Location: MSHCP > VOLUME 2 > BIRDS
American bittern (Botaurus lentiginosus)
State: None
Federal: Species of Management Concern; Partners in Flight Priority Bird Species
The American bittern is sparsely-distributed throughout the MSHCP Plan Area within its suitable habitat, however, it is not predictably distributed within all suitable areas. It is found in margins surrounding open water bodies, and freshwater marshes where emergent vegetation is present. There are several likely Core Areas for this species based on past use by the American bittern or presence of suitable habitat, including Mystic Lake/San Jacinto Wildlife Area, Santa Ana River/Prado Basin, and Collier Marsh. The breeding locations (possibly at Mystic Lake/San Jacinto Wildlife Area [Garrett and Dunn 1980] and Santa Ana River/Prado Basin [L. Hays, pers. obs.]) which have been documented as active or possible are located at specific sites that require conservation. Because it is well known for using emergent habitat but has specific breeding location requirements, it is anticipated that this species will respond to a landscape level of management with site specific requirements.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 410 acres of suitable nesting and foraging habitat for the American bittern consisting of freshwater marsh.
Include within the MSHCP Conservation Area at least 3 Core Areas including Mystic Lake/San Jacinto Wildlife Area (Subunit 4 of RecheCanyon/Badlands Area Plan; 2,690 acres), a possible nesting area, Santa Ana River/Prado Basin (9,670 acres), a known nesting area, and Collier Marsh (Proposed Linkage 2; 160 acres), a potential nesting area, as well as other suitable habitat locations at Lake Skinner/Diamond Valley Lake (Existing Core J; 24,370 acres), Lake Mathews (Existing Core C; 15,610 acres), Vail Lake (Subunit 3 of Southwest Area Plan; 12,320 acres), Temescal Wash (Subunit 3 of Temescal Canyon Area Plan; 4,010 acres), and Temecula Creek (Subunit 2 of Southwest Area Plan; 850 acres).
A 100-meter buffer will be established around emergent vegetation areas identified in Objective 2 as they are incorporated into the MSHCP Conservation Area.
Within the MSHCP Conservation Area, maintain (once every 8 years) the continued use of 50 percent of the Core Areas.
The American bittern is virtually restricted to dense beds of cattails and rushes within freshwater and brackish water systems (Garrett and Dunn 1988). For the purpose of the conservation analysis, potential habitat for the American bittern includes freshwater marsh habitat. In addition, although not quantified, potential habitat includes the margins surrounding open water bodies that may contain desirable emergent plant communities suitable for foraging and nesting opportunities. Based on these habitats, the Plan Area supports approximately 470 acres of potential habitat for the American bittern. Table 1 shows the conservation and loss of potential habitat for the American bittern. Overall, approximately 410 acres ( 87 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public Lands.
TABLE 1
SUMMARY OF HABITAT CONSERVATION FOR
AMERICAN BITTERN
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| All Bioregions | |||||||
| Freshwater Marsh | 470 | 170 | 240 | 410 | 0 | 60 | 60 |
| TOTAL | 470 | 170 (36%) |
240 (51%) |
410 (87%) |
0 (0%) |
60 (13%) |
60 (13%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
The Riparian/Riverine Areas and Vernal Pools policy described in Section 6.1.2 of the MSHCP, Volume 1, provides for conservation of wetlands and riparian values which will protect some habitat as well as important hydrologic functions for this species through avoidance and minimization. Mitigation for impacts to wetlands shall be incorporated in accordance with the "No Net Loss" policy of federal and state wetland regulations. The proposed mitigation shall be directly related to the functions and values of the wetland as related to this species and result in equivalent replacement.
As described below under Data Characterization, six of the eight recent point localities have a high location precision. Of these six point localities, all will be inside the Criteria Area or Public/Quasi-Public Lands. In addition, the one known nesting and one possible nesting location are within the Criteria Area or Public/Quasi-Public Lands. Also, the Core Area at Collier Marsh is within the Criteria Area or Public/Quasi-Public Lands. The other potential areas that contain suitable habitat, Lake Skinner (Existing Core J; 24370 acres), Lake Mathews (Existing Core C; 15610 acres), Vail Lake (Subunit 3 of Southwest Area Plan; 12,320 acres), Temescal Wash (Subunit 3 of Temescal Canyon Area Plan; 4,010 acres), and Temecula Creek (Subunit 2 of Southwest Area Plan; 850 acres), also are within the Criteria Area or Public/Quasi-Public Lands. Conservation of this species will be from a landscape perspective because the species is relatively difficult to detect yet has specific habitat requirements. Additionally, there are definable locations for focusing conservation efforts, and there are two important locations for breeding that are essential for conservation for the species.
Several areas of emergent habitat that contain the current known nesting locations, possible nesting locations, and potential foraging and nesting locations of the American bittern will be conserved in the Criteria Area and Public/Quasi-Public designations including the Prado Basin/Santa Ana River, Mystic Lake/San Jacinto Wildlife Area, Collier Marsh, Lake Skinner, Lake Mathews, Vail Lake, Temescal Wash, and Temecula Creek. Additionally, as these areas are incorporated into the MSHCP Conservation Area the margins surrounding these open water areas will be included in the MSHCP Conservation Area as well. As identified above, the species occurs within the MSHCP Plan Area predominantly as a transient or migrant and, as such, the MSHCP Conservation Area will provide adequate habitat for foraging during nomadic visits to the area and migratory stopovers as well as habitat containing potential nest sites with adequate protection around each nest site and foraging areas during the breeding season. Foraging areas are provided in suitable locations at Vail Lake, Lake Skinner, Mystic Lake/San Jacinto Wildlife Area, Collier Marsh, Lake Mathews, and Prado Basin/Santa Ana River. Potential and likely nest sites are provided in the Mystic Lake/San Jacinto Wildlife Area and known nesting areas are provided in the Prado Basin/Santa Ana River. These MSHCP Conservation Area areas are linked as well, however the American bittern, due to its ability to move long distances and nomadically, may rely less on the linkage than other species.
In summary, conservation for this species will be achieved by inclusion of at least 410 acres of suitable Conserved Habitat including freshwater marsh and the three Core Areas (including the two known or possible nest sites within the Prado Basin/Santa Ana River, Mystic Lake/San Jacinto Wildlife Area, and Collier Marsh) as well as the suitable locations at Lake Skinner, Lake Mathews, Vail Lake, Temescal Wash, and Temecula Creek. The current population size of the American bittern is unknown due to its very secretive nature.
About 60 acres (approximately 13 percent) of potential habitat for the American bittern will be outside the Criteria Area and Public/Quasi-Public areas and individuals within these areas will be subject to Incidental Take consistent with the Plan. Not-conserved habitat includes the margins surrounding Hemet Lake and Lake Riverside. Covered activities in these areas will be subject to the Protection of Species Associated with Riparian/Riverine Areas and Vernal Pools policy included in Section 6.1.2, Volume I of the MSHCP which calls for avoidance and minimization of impacts to wetlands.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The UCR location database contains a total of 18 records dated from 1900 to 1999. A total of eight of these records are recent, (within the past 10 years) and six of these recent records are precise records and could be accurately located within the Plan Area. The habitat types for these records include alkali playa, riparian, marsh, chaparral, and sage scrub, as well as one residential habitat record. This residential record may either no longer be extant or could have been located within a localized marsh within a residential development. Overall, the database records indicate that the American bittern is present within the Plan Area but in relatively low numbers.
The amount of literature available for the American bittern is relatively low. The species is secretive and located within a habitat within which it is difficult to conduct surveys and studies. The literature contains general biology information and some population studies and very little is available for the Plan Area other than general distribution studies.
American bitterns in California are found almost exclusively in emergent habitat of freshwater marshes and vegetated borders of ponds and lakes (Grinnell and Miller 1944). It may occur in sparsely vegetated wetlands occasionally and in tidal marshes rarely (Gibbs et al. 1992). It usually hides, rests, and roosts solitarily amidst tall, dense, emergent vegetation, on the ground, or near the ground on a log, stump, or on emergent plants. It does not normally perch in trees. It feeds in marshes, meadows, and along the edges of shallow ponds (Terres 1980). It also nests within emergent marshes within cattails, cordgrass, sedges, grasses, sedges of a wet meadow or marsh (Terres 1980). It will inhabit wetlands of all sizes but is more abundant on larger wetlands and may prefer impoundments and beaver-created wetlands to wetlands of glacial origin.
American bitterns breed locally from southeastern Alaska eastward to Newfoundland southward to southern California and Virginia; they have also bred (at least formerly) on the Mexican plateau. The species winters from British Columbia eastward to northern Florida south through (at least) Mexico and Cuba (AOU 1998).
The dependence on inland, freshwater marshlands suggests that this species may be a relict over much of the U.S. Historically, the range may have shifted northward, tracking the distribution of wetlands created by retreating glaciers. Breeding Bird Survey sighting frequencies indicate this species is more abundant in Canada than in the U.S., declining sharply below the northern border states. Thus it may be adapted primarily to northern climates and wetlands and now occurs sparsely in the U.S. over what represents the southern edge of its breeding range. Population declines in the U.S. may represent a hastening of an ongoing northern retreat by the species, in part because of habitat destruction in the southern portion of its range (Gibbs et al. 1992).
Zeiner. et al. (1990) describe the distribution, abundance, and seasonality as follows: the American bittern is distributed widely in winter in fresh emergent wetlands, primarily west of the Sierra Nevada. In the Central Valley, it is fairly common October to April, and uncommon to rare the rest of the year; although it breeds there. It is less common on the coastal slope, and no longer breeds regularly south of Monterey County (Garrett and Dunn 1981). In Imperial Valley and along Colorado River, it is fairly common October to April, rare through the summer, and may breed at the northern end of the Salton Sea. In the northeast plateau and east of the Sierra Nevada crest south to Lake Tahoe, it is rare from May to August; it breeds locally. It is rare August to May in saline emergent wetlands along the coast. Elsewhere in the lowlands, it is a rare transient and local winter resident (Cogswell 1977, McCaskie, et al. 1979, Garrett and Dunn 1981). Within coastal southern California, the species is primarily a winter visitor, with nesting occurring only rarely in the coastal plain (Garrett and Dunn 1981).
The small breeding population in the lowlands may be nonmigratory; it may be augmented during October to April by migrants, probably from north of California and from the northeastern plateau, which is deserted in winter by this species (Zeiner, et al. 1990).
Although American bitterns have been repeatedly recorded in the San Jacinto Wildlife Area/Mystic Lake area and it possibly breeds there (Garrett and Dunn 1981) the only known breeding location is at the Prado Basin (L. Hays, pers. comm.).
Geographic locations recorded within the U.C. Riverside database include: Temecula Creek, Temescal Wash, Lake Mathews, Santa Ana River/Prado Basin, Lake Elsinore, Lake Perris, and Mystic Lake/San Jacinto Wildlife Area. These records do not confirm breeding locations but the habitat is present and breeding could occur in these regions or the area may be used for foraging. American bitterns are secretive birds and may escape detection in the absence of relatively intensive, focused surveys.
Genetics: The American bittern is the smallest of the four species of Botaurus bitterns. Within the genus, the American bittern and south American bittern differ sufficiently in skeletal characteristics from one another and from the old world bitterns to be considered separate species (Gibbs et al. 1992). The species is monotypic and available data do not support the subspecific differentiation of birds from the eastern versus western North America (Gibbs et al. 1992).
Diet and Foraging: The American bittern forages within the emergent vegetation and shallow water of fresh or saline wetlands (Zeiner, et al. 1990). It feeds less often in adjacent shallow water of lakes, backwaters of rivers, or estuaries; and occasionally along adjacent shores. It feeds most actively at dusk or at night (Terres 1980), but also apparently at any time of day. It stands motionless and waits for prey, or stalks very slowly; it grasps the prey in the bill with a quick strike (Kushlan 1976b). It eats mainly insects, amphibians, fish, crayfish, and small mammals; also snakes, miscellaneous invertebrates, and birds.
Daily Activity: The American bittern is a year-long, circadian feeder, but most activity is crepuscular and nocturnal (Zeiner, et al. 1990).
Reproduction: The nest of the American bittern is a platform of matted, emergent aquatics, other herbaceous stems, sticks and/or leaves, usually in shallow water, but sometimes floating, or on the ground. It nests within the emergent vegetation and shallow water of fresh or saline wetlands (Zeiner, et al. 1990). Within the Prado Basin, the birds possibly breed in ponds with substantial tule/bulrush cover (L. Hays, USFWS, pers. obs.). The timing of courtship and nest-building is unknown; eggs or young have been reported April to July (Cogswell 1977). It is possibly polygamous, based on minimal evidence. It is basically a solitary nester, but is often in the vicinity of other pairs. The clutch size is usually 3-5 eggs, with a range of 2-6 eggs. It is apparently single-brooded. Incubation is about 24 days. The semi-altricial, downy hatchlings are apparently tended solely by the female, and remain in the nest about two weeks.
Survival: Little information is available. One banded individual of the American bittern lived at least 8 years (Gibbs et al. 1992).
Dispersal: Ages at first flight, independence, and first breeding of the American bittern are unknown (Palmer 1962). The American bittern is thought to undergo extensive, postbreeding dispersal which may account for the number of sightings, mostly in September through December in locations as distant as Iceland, Norway and Great Britain (Gibbs et al. 1992).
Socio-Spatial Behavior: In a slough in Saskatchewan, less than 16 hectares (40 acres) in extent, there were five nests of the American bittern (Bent 1926). Distances between nests have been as little as 18 meters (57 feet) in Michigan (Middleton 1949), 37 meters (120 feet) in lowa (Provost 1947), and 46 meters (150 feet) in Minnesota (Vesall 1940). The territory is probably used mainly for courtship, copulation, and nesting; size is unknown (Palmer 1962).
Community Relationships: No information is available within the literature.
American bitterns apparently historically were more common and widespread in coastal southern California (Garrett and Dunn 1981). As early as the 1940's, Grinnell and Miller (1944) noted that the "extent of distribution and numbers have been diminishing concurrently with the effacement of appropriate habitat." The population has declined due to the draining of marshes, human disturbance, and pesticides. Overgrazing of emergent vegetation also is detrimental to the species. (Arbib 1979).
American bitterns have been known to nest within restored bulrush marsh areas, a floodwater storage pool and even various kinds of upland vegetation, although this is rare (Svedarsky 1992). The species may also make use of wetlands created by surface mining (Perkins and Lawrence 1985).
Habitat degradation is also a factor in causing changes in the population size of the American bittern. Eutrophication, siltation, chemical contamination, and human disturbance may seriously reduce habitat quality, primarily by damaging the prey supplies. Changes in wetland isolation and stabilized water regimes may seriously erode habitat quality for bitterns (Gibbs et al. 1992).
Preservation of freshwater wetland habitats, particularly large (greater than 10 hectares) shallow wetlands with dense growths of robust emergents is the most urgent management need. Wetlands used for breeding by American bitterns also need to be protected from chemical contamination, siltation, eutrophication, and other forms of pollution that harm the birds or their food supplies (Gibbs et al. 1992).
Arbib, R. 1979. The blue list for 1980. American Birds 33: 830-835.
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Bent, A. C. 1926. Life histories of North American marsh birds. U.S. Natl. Mus. Bull. 135. 490pp.
Cogswell, H. L. 1977. Water birds of California. Univ. California Press. Berkeley 399 pp.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Gibbs, J.P., S. Melvin, and F. A. Reid. 1992. American Bittern. The Birds of North America 18: 1-12.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Copper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April, 1986. 617 pp.
Kushlan, J. A. 1976b. Wading bird predation in a seasonally fluctuating pond. Auk 93:464- 476.
McCaskie, G., P. De Benedictis, R. Erickson, and J. Morlan. 1979. Birds of northern California, an annotated field list. 2nd ed. Golden Gate Audubon Soc., Berkeley. 84pp.
Middleton, D. S. 1949. Close proximity of two nests of American bitterns. Wilson Bull. 61:113.
Palmer, R. S., ed. 1962. Handbook of North American birds. Vol. 1. Yale University Press, New Haven, CT. 567pp.
Perkins, G. A. And J. S. Lawrence. 1985. Bird use of wetlands created by surface mining. Trans. Ill. State Acad. Sci. 78: 87-96.
Provost, M. W. 1947. Nesting of birds in the marshes of northwest Iowa. Am. Midl. Nat. 38:485-503.
Sverdarsky, W. D. 1992. Observations on nesting of the American bittern in northwest Minnesota. Prairie Naturalist 24: 241-250.
Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. A. Knopf, New York. 1100pp.
Vesall, D. B. 1940. Notes on nesting habits of the American bittern. Wilson Bull. 52:207- 208.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
bald eagle (Haliaeetus leucocephalus)
State: Endangered; Fully-Protected Species; California Department of Forestry and Fire Prevention Sensitive
Federal: Threatened (Federal Register 60:36010, July 12, 1995); Partners in Flight Priority Bird Species; Bald Eagle Protection Act of 1940
The bald eagle was initially listed on February 14, 1978 as an endangered species throughout the lower 48 states, except in Minnesota, Michigan, Wisconsin, Washington, and Oregon, where it was listed as a threatened species. On July 12, 1995, the USFWS announced that the bald eagle would be reclassified from endangered to threatened in the lower 48 states, effective August 11, 1995. In those states where the species was already listed as threatened, it remains classified that way but was proposed for delisting in July 1999.
The bald eagle has a wide distribution throughout the MSHCP Plan Area within its suitable habitat. It occurs or has occurred at every open water body within the Plan Area. It uses suitable habitat predictably and responds well to available suitable habitat. It occurs within the Plan Area predominantly as a winter visitor with casual occurrences in the summer of individuals that have lingered at the wintering sites. It has attempted to breed at Lake Elsinore and at Lake Skinner but has not done so successfully.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 10,340 acres of open water habitat at the following seven open water bodies and one drainage: Lake Mathews, Diamond Valley Lake, Lake Skinner, Lake Elsinore, Vail lake, Lake Perris, Mystic Lake and Santa Ana River. Include within the MSHCP Conservation Area 5,520 acres of suitable riparian habitat within the Prado Basin and Santa Ana River.
A 100-meter buffer will be established around open water bodies identified in Objective 1 as they are incorporated into the MSHCP Conservation Area.
For the purpose of the conservation analysis, potential habitat for the bald eagle includes open water lakes and reservoirs, a shoreline buffer of 100 meters around each of the open water lakes and reservoirs, and the riparian habitat within the Prado Basin and Santa Ana River. Although the bald eagle has not recently bred successfully within the MSHCP Plan Area, potential breeding habitat does occur around several of the water bodies. Based on these habitats, the Plan Area supports approximately 18,000 acres of potential habitat for the bald eagle. Table 1 shows the conservation and loss of potential habitat for the bald eagle. Overall, approximately 15,860 acres (88 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public lands.
As described below under Data Characterization, 8 of the 17 recent point localities have a high location precision. Of these eight point localities, three will be inside the Criteria Area or Public/Quasi-Public Lands. However, of the five points located outside these habitat areas, all are mapped in existing residential/urban/exotic areas or in existing agriculture or other upland habitats. These habitats do not constitute suitable habitat but these locations may have been of a bird flying overhead or within habitat adjacent to one of the reservoirs. Conservation of this species is being considered from a landscape perspective because the species is found throughout the Plan Area and is well documented for the type of habitat within which they forage. While there are definable locations for focusing conservation efforts, these do not constitute Core Areas. Any nesting locations identified will be important to preserve.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
BALD EAGLE
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| All Bioregions | |||||||
| Open Water | 12,210 | 1,190 | 9,150 | 10,340 | 40 | 1,830 | 1,870 |
| Riparian Habitat within Prado Basin/Santa Ana River | 5,790 | 510 | 5,010 | 5,520 | 0 | 270 | 270 |
| TOTAL | 18,000 | 1,700 (9%) |
14,160 (79%) |
15,860 (88%) |
40 (<1%) |
2,100 (12%) |
2,140 (12%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Several large blocks of habitat supporting the current known locations and potential foraging and nesting locations of the bald eagle will be conserved as Criteria Area and Public/Quasi-Public designations, including the Prado Basin, Santa Ana River, Lake Skinner, Diamond Valley Lake, Lake Mathews, Lake Perris, Mystic Lake, Lake Elsinore, and Vail Lake. The MSHCP Conservation Area will provide adequate habitat for foraging during winter, nomadic visits to the area, and migratory stopovers. The MSHCP Conservation Area will also provide potential nest sites and foraging areas during the breeding season. Foraging areas are provided at Vail Lake, Lake Skinner, Diamond Valley Lake, Lake Perris, Mystic Lake, Lake Elsinore, Lake Mathews, Prado Basin and Santa Ana River. Potential perching and nest sites are provided at these open water/reservoir areas in the form of large trees or snags within the 100 meter wide buffer around each water body. The bald eagle, due to its ability to move long distances, will rely less on the linkages between potential breeding areas than other species.
In summary, conservation for this species will be achieved by inclusion of at least 15,860 acres of suitable Conserved Habitat including open water bodies and riparian habitat within the Santa Ana River and Prado Basin. The current population size of the bald eagle is unknown because it is primarily a winter and transient visitor. However, a single pair has made repeated, but unsuccessful, attempts to breed at Lake Skinner in recent years.
The estimated Take of the bald eagle is based on the acreage of potentially suitable and/or occupied habitat. About 2,140 acres (12 percent) of potential habitat for the bald eagle will be outside the Criteria Area and Public/Quasi-Public designations and individuals within these areas will be subject to Incidental Take consistent with the Plan. Potential habitat not included within the MSHCP Conservation Area includes the open water habitat at Hemet Lake and Lake Riverside.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The UCR location database for the bald eagle includes a total of 31 records dated from 1973 to 1999. All but one of these records is from local biologists reports; a survey conducted in 1996 by the USFWS reported one location record. A total of 17 of these records are relatively recent (within the past 10 years) and of these recent records, a total of 8 are of high precision. The habitats with which these records are associated includes grassland, chaparral, riparian, croplands, residential, and open water. The upland and residential habitat location records probably reflect observations of a bald eagle in flight over an area.
The literature available on the bald eagle is fairly extensive for a number of reasons, not the least of which is the fact that the bald eagle is our Nation's symbol. It has been studied for many years by ornithologists interested in raptors. Due to its listed status, the pesticide problems to which were attributed its population decline a number of years ago, as well as the interest in its recovery from its population decline, a large number of natural history articles as well as summary information within the general ornithological literature is available. Little information is available that pertains directly to the Plan Area other than general distribution information.
Range-wide, bald eagles occur primarily at or near seacoasts, rivers, swamps, and large lakes (AOU 1998). It is considered a bird of aquatic ecosystems but within such areas, it must have an adequate food base, perching areas, and nesting sites to support them (Gerrard and Bortolotti 1988). Perching sites need to be composed of large trees or snags with heavy limbs or broken tops (USFS pers. comm. 1999). The bald eagle nests in trees, rarely on cliff faces and ground nests in treeless areas and always relatively close to water with suitable foraging opportunities. The actual distance to water varies within and among populations of the bald eagle. In some cases, the distance to water is not as critical as the quality of the foraging area. The quality of the foraging areas is defined by the diversity, abundance, and vulnerability of the prey base, the structure of aquatic habitat such as the presence of shallow water and absence of human development and disturbance (Buehler 2000). The diurnal perch habitat is characterized by presence of tall, easily accessible, often super-canopy trees adjacent to the shoreline foraging habitat. The perch tree species used by the bald eagle are highly variable, including both coniferous and deciduous species if present. Most perch trees are live trees although dead trees may be preferred if available. The bald eagle selects a wider range of tree species and sizes for perching than for nesting or roosting (Buehler 2000).
Within southern California, although birds are found in these same habitats, they are most often recorded at large deep inland bodies of water and are considered a winter resident that in the past may have bred in the area (Garrett and Dunn 1981). In winter, bald eagles often congregate at specific wintering sites that are generally close to open water and that offer good perch trees and night roosts. The bald eagle may roost communally in winter in dense, sheltered, remote conifer stands (Zeiner, et al. 1990). In Klamath National Forest, winter roosts were 16-19 kilometers (10-12 miles) from feeding areas (Spencer 1976). The bald eagle often concentrates in large numbers on the wintering grounds. The winter habitat suitability is defined by the food availability, the presence of roost sites that provide protection from inclement weather and absence of human disturbance although bald eagles will tolerate some human activity in areas of high prey availability. The perching habitat during the wintering season is characterized by the presence of tall trees located adjacent to foraging areas similar to other times of the year (Buehler 2000).
The bald eagle is the only sea eagle regularly occurring on the North American continent. Bald eagles breed locally from Alaska eastward to Newfoundland southward locally to Baja California, Sonora, Texas, and Florida. The species winters in the large majority of the breeding range but generally withdraws from central Alaska and the central and the northern portions of Canada (AOU 1998). Individuals that breed in California may make only local winter movements in search of food.
Within mainland southern California, the species primarily winters at larger bodies of water in the lowlands and mountains (Garrett and Dunn 1981). It is fairly common as a local winter migrant at a few favored inland waters in southern California. Largest numbers occur at Big Bear Lake, Cachuma Lake, Lake Mathews, Nacimiento Reservoir, San Antonio Reservoir, and along the Colorado River (Zeiner et al. 1990). Recent breeding attempts on the mainland south of Santa Barbara County (e.g., Silverwood Lake, Lake Skinner, Lake Perris) have been unsuccessful (K. Cleary-Rose, pers. comm., 2002).
The historic breeding range of the bald eagle is probably similar to the present breeding distribution with major changes, both losses and gains of breeding areas in the twentieth century. The distribution reported by Oberholser (1906) is very similar to the present distribution (Buehler 2000).
Notwithstanding failed nesting attempts (see "Current Range" above) by summering or resident birds, the bald eagle is primarily a migrant and wintering species within western Riverside County. Although the species remains nowhere common and is generally rare and local in southern California (Garrett and Dunn 1981), the species could turn up virtually anywhere within western Riverside County in suitable habitats and may, in fact, attempt to nest. Thus, as a species occurring within the area in the summer, it is considered a casual occurrence. Generally, however, it is considered a very localized winter visitor that is fairly common at a few favored wintering sites around inland bodies of water yet is generally very rare otherwise (Garrett and Dunn 1981).
Birds have been detected in recent years at the Prado Basin, Lake Skinner, Lake Mathews, and Lake Perris. There are also records from Lake Elsinore, where the species may have bred in the past (Garrett and Dunn 1981), and the species has been observed infrequently at Lake Hemet and Vail Lake. Recently, the bald eagle has attempted to breed at Lake Skinner. Up to 20 eagles were reported to be present at Lake Mathews (Garrett and Dunn 1981).
Genetics: There are eight species in the genus Haliaeetus which are distributed worldwide except in South America. The genus is most closely related to the other fish eagles and is perhaps also related to the scavenging kites and to the Old World vultures. The bald eagle is likely most closely related to and may constitute a superspecies with the white-tailed eagle (H. Albicilla) (Buehler 2000).
Diet and Foraging: Fish predominate the typical diet of bald eagles, however, many other types of prey are also taken, including waterfowl and small mammals, and carrion especially in the wintering areas (USFWS 1995). It swoops from hunting perches, or soaring flight to pluck fish from water. It is also known to wade into shallow water to pursue fish. It may pounce on, or chase, injured or ice-bound water birds. In flooded fields, the species occasionally pounces on displaced voles, or other small mammals. Open, easily approached hunting perches and feeding areas are used most frequently (Zeiner, et al. 1990). Bald eagles tend to hunt cooperatively (Brown 1999). Studies of prey items in northern California, showed bald eagles do not differentiate between native and non-native freshwater fish species (Jackman, et al. 1999). One study of birds in Texas found them to eat a relatively equal proportion of birds, reptiles and fish (Mabie, et al. 1995). One wintering population in the lower Great Lakes basin was observed feeding on carcasses of white-tailed deer during 47 percent of observed feedings (Ewins and Andress 1995). The same group observed immature individuals feeding on garbage and offal 39 percent of feedings.
Daily Activity: Wintering bald eagles in New Mexico spent 95.3 percent of their time perched and 4.7 percent in flight (Zwank, et al. 1996). Of the time spent in flight, 13.0 percent was spent foraging (Zwank, et al. 1996). Winter feeding usually occurs immediately after dawn and in late afternoon (Zeiner, et al. 1990).
Reproduction: Breeding of the bald eagle occurs in open areas, near water, with nests often in large snags or old-growth trees (Brown 1999). The bald eagle also nests in a dominant live tree with open branch work, especially ponderosa pine. It nests most frequently in stands with less than 40 percent canopy, but there is usually some foliage shading the nest (Call 1978). It often chooses the largest tree in a stand on which to build its stick platform nest. The nest may be a massive structure, twelve feet high, eight and a half feet across and with a wet mass of decaying vegetation in the center, weighing many hundred pounds (Brown and Amadon 1968). The nest is typically located 16-61 meters (50-200 ft) above ground, usually below the tree crown. The species of tree that is used for locating the nest site is apparently not so important as the height and size. The nest is usually located near a permanent water source. In California, 87 percent of the nest sites of the bald eagle were within 1.6 kilometers (1 mile) of water. Individuals have been known to use the same nest for up to 35 years (Brown 1999).
The clutch size of the bald eagle is usually two, but can vary from one to three, and eggs are laid once annually (Brown 1999). The bald eagle breeds from February through July, with a peak in activity from March to June. Incubation of the eggs usually lasts 34-36 days. The semi-altricial young hatch asynchronously (Ehrlich, et al. 1988). The species is monogamous, and breeds first at 4-5 years (Zeiner, et al. 1990).
Survival: In one study of bald eagle nests in British Colombia, Canada, food supply was identified as the "key factor" in limiting breeding success (Elliot, et al. 1998). Because of the asynchronous hatching the older nestling may kill the younger, smaller sibling if the food supply is inadequate (Brown and Amadon 1968). The recorded longevity in the wild is 28 years and 36 years in captivity. Bald eagles may follow the survival pattern similar to other raptors with lower first-year survival followed by increasing survival to adulthood. Adult survival is high in most studies on survivorship (Buehler 2000).
Dispersal: The young of the bald eagle leave the nest 70 to 98 days after hatching but do not reach breeding age until four or five (Brown 1999). A mark-recapture study of a breeding population in Texas concluded that birds fledged there may disperse to breeding communities throughout the southern United States (Mabie, et al. 1994).
Socio-Spatial Behavior: The bald eagle home range of resident pairs on the Columbia River averaged 22 km2 for both breeding and non-breeding periods (Garrett, et al. 1993). The breeding territory in Alaska (n= 14), varied from 11-45 hectares (28-112 acres), and averaged 23 hectares (57 acres) (Hensel and Troyer 1964). The breeding territory is defended from the mating through the fledging period of the pair. Minimum distances between bald eagle nests were 1 kilometer (0.6 miles) in Alaska, and 17 kilometers (10 miles) in Washington (Zeiner, et al. 1990).
Community Relationships: The bald eagle competes with, and steals prey from osprey (Zeiner, et al. 1990). It has been observed causing a turkey vulture to disgorge its food (Brown and Amadon 1968).
Habitat loss, the expressed effects of select pesticides on reproductive success, and persecution of the species necessitated the listing of the bald eagle. The use of DDT after World War II led to eggshell thinning which drastically reduced reproductive success and the species' populations (USFWS 1995). The species does not occupy its former breeding range in southern California or occur in numbers comparable to historical totals (Grinnell and Miller 1944 and Garrett and Dunn 1981). However, successful captive breeding efforts, the banning of certain organochlorine pesticides, and other recovery efforts have resulted in apparent, significant increases in eagle numbers on the continent. Special pressures on individuals in the southwestern United States include: heat stress, nest parasites and entanglement in fishing line debris from intense fishing pressure (USFWS 1995).
A study of nests in Oregon identified the following causes of nest failures: pesticides (32 percent), proximity to nearest-neighbor breeding pairs (11 percent), infertile eggs (7 percent), nestling mortality (3 percent), human disturbance (2 percent), changes in members of a pair (1 percent), and unknown causes (21 percent) (Anthony, et al. 1994).
Human recreational use of reservoirs and rivers occupied by bald eagles has been greatly studied (Stalmaster and Kaiser 1998). Territories have been abandoned after there has been disturbance from logging, recreational development, and other human activities near nests of the bald eagle (Thelander 1973). In northwest Washington, feeding activity was found to decline exponentially with increased recreational activity (Stalmaster and Kaiser 1998). Foot traffic caused the greatest flushing distance but boat activities accounted for a greater proportion of the disturbances (Stalmaster and Kaiser 1998).
Bald eagles are sensitive to human encroachment and disturbance. Currently, over one million dollars in public and private money is spent each year toward recovery and protection of bald eagle populations (USFWS 1995). These efforts have increased populations from 417 active nests in the lower 48 states in 1963, according to the National Audubon Society, to 4,450 in 1994 (USFWS 1995).
Researchers recommended that recreational activity during the breeding season be restricted during the first five hours of sunlight where bald eagles are present (Stalmaster and Kaiser 1998). Another study in Arizona found 22-times more eagles nesting in areas with low human use compared to areas with moderate or high human use (Brown and Stevens 1997).
The variable effects of human activity on the reproductive performance of bald eagles implies a threshold for detrimental impact between pristine isolation and outright destruction. Management concepts to protect nesting bald eagles have evolved from concentric-circles buffer zones at nest sites through single territory zonation to a multiple territory regional approach (Grubb and King 1991). Additional research has concluded that management of potentially disturbing human activity near breeding bald eagles should be based on multivariate considerations of action and reaction (Grubb and King 1991). Distance to disturbance is the most important aspect of human disturbance. Human activities that are distant, of short duration, out of sight, few in number, below, and quiet have the least impact. Despite the multi-dimensional nature of human disturbance, any category of disturbance can, in excess or under the proper circumstances, disrupt normal behavior or cause nesting failure. Importance of disturbance groups varies with their associated characteristics. This study suggests a minimum, generic, primary zone of approximately 600 meters around breeding bald eagles (Grubb and King 1991). A 1,200-meter secondary buffer zone would accommodate most of the distant responses from vehicle, noise, and aircraft disturbance. Typically, no human activity is permitted at any time within a primary protection zone. Within a secondary buffer zone, limited, nonpermanent activity may be allowed during the non-breeding season. Other buffer distances of similar magnitudes have been suggested by other researchers for breeding bald eagles (summarized in Grubb and King 1991). This study has provided additional specific distances based on the general category of the disturbance. These values will be useful for management purposes in the event that the bald eagles located within the western Riverside County area attempt to breed. The management recommendations from Grubb and King (1991) for buffer distances for specific activities in association with breeding bald eagles are as follows: Pedestrian disturbance - complete restriction at 543 meters; aquatic disturbance - restriction at 200 meters; vehicle disturbance - complete restriction at 450 meters and limited vehicular control at 850 meters; noise disturbance (includes gunshot and sonic booms) - restrictions within 1,000 meters but may need extending up to 2,000 meters; aircraft disturbance - exclusion within 625 meters and limited flights within 1,100 meters.
The bald eagle was one of four wintering raptor species shown to be sensitive to urbanization, having a threshold of approximately five to seven percent urbanization (Berry, et al. 1998). A group of researchers have used perch tree abundance and shoreline development measures to accurately predict numbers of bald eagles (Chandler, et al.1995).
Human disturbance activities may elicit various responses from wildlife and differences in persecution histories result in diverse wildlife responses to different activity types. The bald eagle is more likely to flush when approached by a human on foot than when approached by an automobile (Holmes et al. 1993). That a person approaching in plain view of a raptor elicits a stronger response than a person within an approaching vehicle suggests that humans approaching slowly are viewed as a greater disturbance than vehicles, which are moving rapidly and screen humans. Some bald eagles have demonstrated habituation to human presence. Wintering bald eagles show lower flushing responses along rivers and estuaries with high levels of recreational boating activity than along adjacent areas with little boating activity (Holmes et al. 1993). However these studies did not monitor the effects of the human disturbances on the reproductive success. Spatial buffer zones are commonly used to protect nesting sites from disturbance, however, buffer zones for wintering raptors also could be effective if placed around sensitive foraging areas. From this study, a buffer zone that would prevent flushing by approximately 90 percent of the wintering individuals of the golden eagle would be set at 300 meters (Holmes et al. 1993). Although this study did not specify the bald eagle and studies were not conducted for bald eagles, presumably the buffer distance for wintering bald eagles might be set for at least as great as the golden eagle until further research determines a different distance is more beneficial.
Because of the selectivity of roost sites by bald eagles (roost trees have greater diameter at breast height, more branching structure and are generally taller than randomly sampled trees) forest harvests should be conducted through selective thinning, prescribed fire and seeding with roost-like trees (Dellasala, et al. 1998).
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Anthony, R. G., R. W. Frenzel, F. B. Isaacs and M. G. Garrett. 1994. Probable causes of nesting failures in Oregon's bald eagle population. Wildlife Society Bulletin 2:576-582.
Berry, M. E., C. E. Bock and S. L. Haire. 1998. Abundance of diurnal raptors on open space grasslands in an urbanized landscape. Condor 100: 601-608.
Brown, B. T. and L. E. Stevens. 1997. Winter bald eagle distribution is inversely correlated with human activity along the Colorado River, Arizona. Journal of Raptor Research 31:7-10.
Brown, N. L. 1999. World Wide Web-site: http://arnica.csustan.edu/esrpp/baldeg.htm.
Brown, L., and D. Amadon. 1968. Eagles, hawks and falcons of the world. 2 Vols. Country Life Books, London. 945pp.
Buehler, D. A. 2000. Bald Eagle (Haliaeetus leucocephalus). Number 506. In The Birds of North America, A. Poole and F. Gill, Eds. Cornell Laboratory of Ornithology and The Academy of Natural Sciences, Washington D.C.
Call, M. W. 1978. Nesting habits and survey techniques for common western raptors. U. S. Dep. Inter., Bur. Land Manage., Portland, OR. Tech. Note No. 316. 115pp.
Chandler, S. K., J.D. Fraser, D. A. Buehler and J. K. D. Seegar. 1995. Perch trees and shoreline development as predictors of bald eagle distribution on Chesapeake Bay. Journal of Wildlife Management 59:325-332.
Cleary-Rose, K. 2002. Pers. comm. U.S. Fish and Wildlife Service.
Dellasala, D. A., R. G. Anthony, T. A. Spies and K. A. Engel. 1998. Management of bald eagle communal roosts in fire-adapted mixed-conifer forests. Journal of Wildlife Management 62:322-333.
Elliot, J. E., I. E. Moul, K. M. Cheng. 1998. Variable reproductive success of bald eagles on the British Columbia coast. Journal of Wildlife Management 62:518-529.
Ewins, P.J. and R. A. Andress. 1995. The diet of bald eagles, Haliaeetus leucocephalus, wintering in the lower Great Lakes Basin, 1987-1995. Canadian Field-Naturalist 109:418-425.
Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder's handbook. Simon and Schuster, New York. 785pp.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Garrett, M G., J. W. Watson and R. G. Anthony. 1993. Bald Eagle Home Range and Habitat use in the Columbia River Estuary. Journal of Wildlife Management 57:19-27.
Gerrard and Bortolotti. 1988. The bald eagle: haunts and habits of a wilderness monarch. Smithsonian Inst. Press, Washington, 177pp.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Copper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April, 1986. 617 pp.
Grubb, T. G. and R. M. King. 1991. Assessing human disturbance of breeding bald eagles with classification tree models. J. Wildl. Management 55: 500-511.
Hensel, R. J., and W. A. Troyer. 1964. Nesting studies of the bald eagle in Alaska. Condor 66:282-286.
Holmes, T., R. L. Knight, and G. R. Craig. 1993. Responses of wintering grassland raptors to human disturbance. Wildlife Society Bulletin 21: 461-468.
Jackman, R. E., W. G. Hunt, J. M. Jenkins and P. J. Detrich. 1999. Prey of nesting Bald Eagles in northern California. Journal of Raptor Research 33:87-96.
Mabie, D. W., M. T. Merendino and D. H. Reid. 1995. Prey of nesting bald eagles in Texas. Journal of Raptor Research 29:10-14.
Mabie, D. W., M. T. Merendino and D. H. Reid. 1994. Dispersal of Bald Eagles Fledged in Texas. Journal of Raptor Research 28: 213-219.
Oberholser, H. C. 1906. The North American eagles and their economic relations. U.S. Dept. Agriculture Biol. Surv. Bull. 27, Washington, D. C.
Spencer, D. A., ed. 1976. Wintering of the migrant bald eagle in the lower 48 states. Natl. Agric. Chem. Assoc. Publ., Wash. DC. 170pp.
Stahlmaster, M.V. and J. L. Kaiser. 1998. Effects of recreational activity on wintering bald eagles. Wildlife Monographs 137: 1-46.
Thelander, C. G. 1973. Bald eagle reproduction in California, 1972-1973. Calif. Dept. Fish and Game, Sacramento. Wildl. Manage. Branch Admin. Rep. 73-5. 17pp.
United States Fish and Wildlife Service. 1995. Endangered and Threatened Wildlife and Plants; Final Rule to Reclassify the Bald Eagle from Endangered to Threatened in all of the Lower 48. Federal Register 50 CFR Part 17, v.60, n.133 July 12, 1995:35999-36010.
United States Forest Service (USFS). 1999. Pers. comm. Species accounts for threatened, endangered and sensitive wildlife species occurring in the San Bernardino National Forest.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
Zwank, P.J., B. L. Tarrant, R. Valdez and D. L. Clason. 1996. Wintering bald eagle populations and behavior in the middle Rio Grande Basin, New Mexico. Southwestern Naturalist 41:149-154.
Bell's sage sparrow (Amphispiza belli belli)
State: Species of Special Concern
Federal: Partners in Flight Priority Bird Species; Species of Management Concern; Federal Special Concern species
Other: Audubon Society California Watch List
The Bell's sage sparrow is widely but sparsely distributed throughout the MSHCP Plan Area within suitable habitat in the Riverside lowlands, Santa Ana Mountains, Desert Transition and San Jacinto Foothills Bioregions. It is absent from higher elevation Bioregions. The Bell's sage sparrow occurs within several areas that appear to be Core Areas including Jurupa Mountains, Lake Mathews-Estelle Mountain, Wasson Canyon, Santa Rosa Plateau, Sedco Hills, Hogbacks, Lake Skinner/Diamond Valley Lake, Vail Lake/Wilson Valley/Aguanga, Tule Valley, Santa Rosa Hills, Lakeview Mountains, Lake Perris, Badlands, and Box Springs Mountains. However, none of these Core Areas contains large or dense populations of the Bell's sage sparrow. The Bell's sage sparrow is a year-round resident within the Plan Area. Because it is well known for using coastal sage scrub and chaparral habitats, occurs widely but sparsely and well scattered within these habitats in the Riverside lowlands, San Jacinto Foothills, Desert Transition, and Santa Ana Mountains Bioregions, but has specific locations that are Core Areas, it is anticipated that this species will respond well to a landscape level of management with site specific requirements.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 245,750 acres of suitable habitat for Bell's sage sparrow including coastal sage scrub, chaparral, and desert scrubs in Riverside lowland, Santa Ana Mountains, Desert Transition, and San Jacinto foothills Bioregions.
Include within the MSHCP Conservation Area at least 12 of 14 Core Areas and interconnecting linkages for Bell's sage sparrow. Core areas will include the Jurupa Mountains (Proposed Noncontiguous Habitat Block 2; 1,230 acres), Lake Mathews-Estelle Mountain (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres), Wasson Canyon (Subunit 5 of Elsinore Area Plan; 2,320 acres), Sedco Hills (Proposed Linkage 8; 5,470 acres), Hogbacks (Proposed Core 2; 5,050 acres), Lake Skinner/Diamond Valley Lake (Existing Core C plus Proposed Extension of Existing Cores 5, 6, 7; 29,060 acres), Vail Lake/Wilson Valley/Aguanga (Proposed Core 7; 50,000 acres), Tule Valley, (Proposed Core 6; 4,290 acres), Lakeview Mountains (Proposed Noncontiguous Habitat Block 5; 7,150 acres), Lake Perris (Existing Core H; 17,470 acres), Badlands (Proposed Core 3; 24,920 acres), and Box Springs Mountains (Existing Noncontiguous Habitat Block A plus Proposed Constrained Linkage 8; 2,920 acres).
Include within the MSHCP Conservation Area habitat linkages between Core Areas and areas important for dispersal including the Jurupa Mountains, Reche Canyon, and San Timoteo Creek areas.
Although the distribution and habitat use of the Bell's sage sparrow is very similar to that of the coastal California gnatcatcher and Southern California rufous-crowned sparrow, the Bell's sage sparrow differs from each of these species in several factors: it occurs at higher elevations similar to the Southern California rufous-crowned sparrow but different from the coastal California gnatcatcher, it occurs in the Desert Transition bioregion, it rarely or never uses grassland habitat except possibly for dispersal, and it is more sparsely scattered at lower populations levels throughout the MSHCP Plan Area. For the purpose of the conservation analysis, potential habitat includes coastal sage scrub, chaparral, and desert scrubs within the Riverside Lowlands, San Jacinto Foothills, Santa Ana Mountains, and Desert Transition Bioregions. Bell's sage sparrow is documented to use the sparse form of chaparral which is included within the broader category of chaparral for the Plan Area (Martin and Carlson 1998). The mapping for the Plan Area does not distinguish between sparse and dense forms of chaparral. Based on these habitats, the Plan Area supports approximately 423,190 acres of potential habitat for the Bell's sage sparrow. Table 1 shows the conservation and loss of potential habitat for the Bell's sage sparrow. Overall, approximately 245,750 acres (58 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public lands for all the habitats combined.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
BELL'S SAGE SPARROW
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Habitats within Riverside Lowlands, San Jacinto Foothills, Santa Ana Mountains, and Desert Transition Bioregions | |||||||
| Desert Scrubs | 7,940 | 3,440 | 1,170 | 4,610 | 40 | 3,290 | 3,330 |
| Coastal Sage Scrub | 148,220 | 45,550 | 32,750 | 78,300 | 25,790 | 44,130 | 69,920 |
| Chaparral | 267,030 | 55,750 | 107,090 | 162,840 | 47,350 | 56,840 | 104,190 |
| TOTAL | 423,190 | 104,740 (25%) |
141,010 (33%) |
245,750 (58%) |
73,180 (17%) |
104,260 (25%) |
177,440 (42%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
This species may occur within Forest Service lands for nesting and foraging within coastal sage scrub, and chaparral in the Santa Ana Mountains bioregion. Currently there are no database records within the Forest Service lands, however, based on the elevation and habitats available within the Cleveland National Forest, it is likely to occur within the area. The locations within the Forest Service lands are expected to be in coastal sage scrub and chaparral habitat within the Cleveland National Forest. Under the existing Forest Land Allocation plan, these potential locations or habitats generally are located within the Wildhorse and Coldwater roadless areas, San Mateo Canyon Wilderness Area and possibly the Tenaja and Verdugo Range Allotments.
As described below under Data Characterization, 98 of the 264 point localities have a high location precision. Of these 98 point localities, 34 (35 percent) will be inside the Criteria Area or Public/Quasi-Public lands. A total of 18 (18 percent) will be in the Rural/Mountainous zone. Of the 46 (47 percent) points located outside the MSHCP Conservation Area, 26 are mapped in existing residential/urban/ exotic areas.
Twelve of fourteen Core Areas will be conserved within the Jurupa Mountains (Proposed Noncontiguous Habitat Block 2; 1,230 acres), Lake Mathews-Estelle Mountain (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres), Wasson Canyon (Subunit 5 of Elsinore Area Plan; 2,320 acres), Sedco Hills (Proposed Linkage 8; 5,470 acres), Hogbacks (Proposed Core 2; 5,050 acres), Lake Skinner/Diamond Valley Lake (Existing Core C plus Proposed Extension of Core 5, 6, 7; 29,060 acres, Vail Lake/Wilson Valley/Aguanga (Proposed Core 7; 50,000 acres), Tule Valley, (Proposed Core 6; 4,290 acres), Lakeview Mountains (Proposed Noncontiguous Habitat Block 5; 7,150 acres), Lake Perris (Existing Core H; 17,470 acres), Badlands (Proposed Core 3; 24,920 acres), and Box Springs Mountains (Existing Noncontiguous Habitat Block A plus Proposed Constrained Linkage 8; 2,920 acres). The total acreage of Core Areas within Criteria Area and Public/Quasi-Public Lands is 173,590 acres. Some additional locations of Bell's sage sparrows will be conserved within the Sycamore Canyon Regional Park, Steele Peak, North Peak Conservation Bank, Motte-Rimrock Reserve, Santa Rosa Plateau Nature Reserve, and Kabian Park. Although only one location is recorded, the MSHCP Conservation Area within the Gavilan Hills provides potential habitat for Bell's sage sparrow.
Conservation also will be provided for the habitat linkages between Core Areas and areas important for dispersal including the Jurupa Mountains, which is also conserved as a Core Area, Reche Canyon, and San Timoteo Creek areas. Other linkages that may be important for this species and that are within Criteria Area and Public/Quasi-Public Lands include the Gavilan Hills as discussed above, Temecula Creek, a Proposed Linkage to Cactus Valley, Tucalota Valley linkage between Lake Skinner/Diamond Valley Lake area and Vail Lake/Wilson Valley/Aguanga area, Tule Creek, Tenaja Corridor, and a linkage between the Santa Rosa Plateau Nature Reserve and the Santa Margarita Ecological Reserve.
Several large blocks of habitat supporting the Bell's sage sparrow will be conserved as Criteria Area and Public/Quasi-Public designations including the Core Areas for the species in the Jurupa Mountains (Proposed Noncontiguous Habitat Block 2; 1,230 acres), Lake Mathews-Estelle Mountain (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres), Wasson Canyon (2,320 acres), Sedco Hills (Proposed Linkage 8; 5,470 acres), Hogbacks (Proposed Core 2; 5,050 acres), Lake Skinner/Diamond Valley Lake (Existing Core C plus Proposed Extended Core 5, 6, 7; 29,060 acres), Vail Lake/Wilson Valley/Aguanga (Proposed Core 7; 50,000 acres), Tule Valley, (Proposed Core 6; 4,290 acres), Lakeview Mountains (Proposed Noncontiguous Habitat Block 5; 7,150 acres), Lake Perris (Existing Core H; 17,470 acres), Badlands (Proposed Core 3; 24,920 acres), and Box Springs Mountains (Existing Noncontiguous Habitat Block A plus Proposed Constrained Linkage 8; 2,920 acres). By conserving these large blocks of habitats, the edge effects of MSHCP Conservation Areas are reduced which may reduce the effects of edge responsive species such as the brown-headed cowbird, invasion of introduced grasses, and human and urban mesopredator intrusion. Some additional locations of the Bell's sage sparrows will be conserved within the MSHCP Conservation Area outside of the Core Areas including the Sycamore Canyon Regional Park, Gavilan Hills, Steele Peak, North Peak Conservation Bank, Motte-Rimrock Reserve, Kabian Park, and Cleveland National Forest (a likely but not confirmed location).
Areas that are important for preservation for dispersal purposes between the Plan Area and other areas, but that may or may not contain large numbers of Bell's sage sparrows, include the Jurupa Mountains for connectivity to San Bernardino County which is also a Core Area for this species, Chino Hills and Cleveland National Forest for connectivity to Orange County, and the Santa Margarita Ecological Reserve and eastern Temecula Creek for connectivity to San Diego County.
Similar to the California gnatcatcher, the Bell's sage sparrow, as a year-round resident, may not be as adept at dispersing as some of the long distance migrant bird species. Unfortunately, no data is available specific to the Bell's sage sparrow, although the sage sparrow has been documented to be sensitive to fragmentation and edge effects (see below). It is assumed, based on the natural history of this species that the MSHCP Conservation Area will provide habitat linkages between the preserved Core Areas. The large block of habitat within the core population area at Lake Mathews-Estelle Mountain Reserve is connected to the Wasson Canyon population along Temescal Wash and the hillsides east of the wash with a wide linkage at a 2,000 foot minimum width. These Core Areas also are connected by the Proposed Linkage at the Gavilan Hills. Connections to the eastern foothills of the Santa Ana Mountains are located at Indian Canyon, and Horsethief Canyon. The Wasson Canyon population is connected to the Hogbacks population along the Sedco Hills Core Area, and then to the Lake Skinner population via the AD161 mitigation area and conservation of other small drainages including Warm Springs, Ken & Barkley Canyon and Tucalota Creek. The Lake Skinner population is linked to the Vail Lake/Wilson Valley/Aguanga area by preservation within the entire area in Wilson Valley as well as the eastern reach of Tucalota Creek. The Cactus Valley area is a large block of habitat connecting the Lake Skinner/Diamond Valley Lake area east to the San Bernardino National Forest, along Bautista Creek and within the large block of habitat within the Badlands. The block of habitat within the Lake Perris Core Area is connected to the Badlands along the San Jacinto River and Lamb Canyon. The Core Area in the Lakeview Mountains is somewhat isolated from other MSHCP Conservation Area areas due to existing development, however a narrow connection is provided between the north edge of the Lakeview Mountains and the San Jacinto River. The Box Springs Mountains area is connected by Reche Canyon to the Badlands.
MSHCP Conservation Area design for the Bell's sage sparrow will take into account that large scale fires damages habitat for a relatively long length of time and large areas are necessary to provide refugia for birds and to supply dispersing individuals to a recovered area. In contradiction to this, and a complicating factor, is that fire may also assist with providing additional suitable habitat for the Bell's sage sparrow. Long term fire suppression in California has allowed some of the shrub communities to reach tall, thick shrublands reducing the availability of suitable habitat. Fire management will be an important factor in addressing the conservation of this species.
Duplicate linkages also provide for the temporary loss of function of the coastal sage scrub or chaparral habitat in the event of a fire. A duplicity of habitat linkages composed of sage scrub and other undeveloped habitats which may be composed of native as well as non-native habitats may provide for dispersal. Several duplicate linkages are preserved in the MSHCP Plan Area including linkages along the Santa Ana Mountains foothills with the Interstate 15 corridor and between AD161 and the Hogbacks and between the Lake Skinner/Diamond Valley Lake area and other areas to the east.
In summary, conservation for this species will be achieved by inclusion of at least 245,750 acres of suitable Conserved Habitat and 12 of 14 Core Areas within large blocks of habitat in the MSHCP Conservation Area. In addition, 34 recent and high precision locations will be inside the Criteria Area or Public/Quasi-Public Lands, all of which are recorded for the suitable habitat of Bell's sage sparrow. Conservation also will be provided for the habitat linkages between Core Areas and areas important for dispersal including the Jurupa Mountains, which is also conserved as a Core Area, Reche Canyon, and San Timoteo Creek areas as well as other linkages as described above. The current population size of the Bell's sage sparrow is unknown. However the habitat requirements of the species and locations that constitute key populations are well documented.
The Incidental Take of the Bell's sage sparrow is difficult to quantify due to our limited knowledge of its distribution and abundance within the Plan Area. The maximum level of Incidental Take of Bell's sage sparrow can be anticipated by the loss of the number of acres of habitat that will become unsuitable for this species. About 177,440 acres of potential habitat for the Bell's sage sparrow will be outside the Criteria Area and Public/Quasi-Public designations, or about 42 percent of the total potential habitat and individuals within these areas are subject to Incidental Take consistent with the Plan. Of this, approximately 73,180 acres (17 percent) of potential habitat are located within Rural/Mountainous designation areas, which may provide some habitat value, but will not be managed for the benefit of covered species and cannot be relied upon as conserved habitat for the Bell's sage sparrow. These areas include the Santa Rosa Plateau, Santa Rosa Hills, and a portion of the Badlands.
Core areas not conserved within Criteria Area and Public/Quasi-Public designations include the Santa Rosa Plateau and Santa Rosa Hills. A total of 64 recent and high precision point locations of the Bell's sage sparrow will be outside the Criteria Area and Public/Quasi-Public designations. Of these 64 point locations, 18 (18 percent) will be in the Rural/Mountainous zone. Of the 46 (47 percent) points located outside the MSHCP Conservation Area, 26 are mapped in existing residential/urban/exotic areas.
The UCR location database contains approximately 352 location records for the Bell's sage sparrow dated from 1887 to 1999. Due to its overlap in habitat with the gnatcatcher, the Bell's sage sparrow has probably been well surveyed within sage scrub habitat. In areas where there is no requirement for surveys for the gnatcatcher, the sage sparrow is likely under represented and the documentation of presence in outlying areas probably has not been accomplished. Approximately 264 of the records are relatively recent (within the past 10 years) and approximately 98 of these records are precise. Approximately 26 of these recent and precise records are located within residential or developed habitats and may no longer be extant, the rest are located within sage scrub, chaparral or other undeveloped habitats and may represent existing locations.
The sage sparrow has a moderate amount of literature available for it. It has been well studied with the suite of species located within the shrub-steppe region and has general natural history information well summarized within the ornithological literature. Although, the subspecies and information for the Plan Area have a relatively little amount of literature available, the species as a whole has been well documented for its distribution and biology.
The sage sparrow prefers semi-open habitats with evenly spaced shrubs 1 to 2 meters high (Martin and Carlson 1998). Vertical structure, habitat patchiness, and vegetation density may be more important in habitat selection by the sage sparrow than the specific shrub species, but this sparrow is closely associated with sagebrush throughout most of its range (Wiens and Rotenberry 1981). The species is often missing from what appears to be suitable habitat, so other unknown habitat characteristics may be important (Martin and Carlson 1998).
Bell's sage sparrow is an uncommon to fairly common but localized resident breeder in dry chaparral and coastal sage scrub along the coastal lowlands, inland valleys, and in the lower foothills of local mountains. In transmontane California, it occupies sagebrush, alkali desert scrub, desert scrub, and similar habitats. In cismontane California, it frequents chaparral dominated by chamise, and coastal scrub dominated by sage. Other coastal scrub plant species associated with Bell's sage sparrow include Artemisia, Purshia, and Atriplex as well as mixed brush and cactus patches in arid washes (Grinnell and Miller, 1944). The preference for chamise chaparral appears to occur only in the more northern parts of its range. High overgrown chaparral stands generally have fewer sage sparrows than shorter shrubs recovering from recent fires (Martin and Carlson 1998). Bell's sage sparrow is also found in big sagebrush at higher elevations in southern mountains (Martin and Carlson 1998).
Bell's sage sparrow seeks cover in fairly dense stands in chaparral and scrub habitats in the breeding season, and they forage on the ground beneath and between shrubs. The species uses similar habitat structure in the winter, however the habitat may be in more arid, open shrub habitats (Zeiner, et al. 1990).
The sage sparrow occurs in western North America from the interior west-central Washington, within the eastern portion of Idaho to western Wyoming, through Nevada, Utah, Colorado south to New Mexico, Arizona and into California. The subspecies Bell's sage sparrow, A. belli belli, occurs as a nonmigratory resident on the coastal ranges of California, on the western slope of the central Sierra Nevada mountains, and into northwestern Baja California (Bent, 1968). Generally it is found throughout the year in southern California and Baja areas where the winter range overlaps with the breeding range (Martin and Carlson, 1998).
Zeiner, et al. (1990) characterized the distribution, abundance and seasonality of the Bell's sage sparrow as follows. It is a common to uncommon resident and summer visitor. In summer, it is uncommon to common east of the Cascade Range and Sierra Nevada, in foothills bounding the Central Valley, and in the Transverse, Peninsular, and coastal ranges from Trinity Co. south to the Mexican border. It is not migratory in many areas, but mostly withdraws from higher elevations and the northern Great Basin in winter and moves to southern deserts. It is most common from the western edge of Owens Valley, Inyo County, south through southern Sierra Nevada and the western edge of Mojave Desert to desert slopes of the Transverse Ranges. On coastal slopes, it is mostly absent north of Sonoma County, and uncommon and local to the south. It occurs only locally at montane elevations, mostly in southern California. The resident race, A. b. clementeae, on San Clemente Island, is classified as a Federally listed threatened species (Grinnell and Miller 1944, McCaskie, et al. 1979, Garrett and Dunn 1981).
The Bell's sage sparrow has a wide but sparse and patchy distribution in western Riverside County. Bell's sage sparrow may occur in extant stands of dry chaparral and coastal sage scrub habitat nearly throughout the Plan Area within the Riverside lowlands, San Jacinto Foothills, Santa Ana Mountains and Desert Transition Bioregions. Although difficult to assign Core Areas to the broad but sparse scatter of database locations some trends of clusters of locations appear to include the areas in the vicinity of Jurupa Mountains, Lake Mathews-Estelle Mountain, Wasson Canyon, Santa Rosa Plateau, Sedco Hills, Hogbacks, Lake Skinner/Diamond Valley Lake, Vail Lake/Wilson Valley/Aguanga, Tule Valley, Santa Rosa Hills, Lakeview Mountains, Lake Perris, Badlands, and Box Springs Mountains (B. Carlson 1998 pers. comm.). Although these areas are considered Core Areas, none of the areas consists of very high or very dense populations except for the Wasson Canyon and Lake Skinner/Diamond Valley Lake areas.
Genetics: The sage sparrow varies in morphometrics, plumage coloration, and habitat selection in correlation with features that roughly agree with observed genetic and biochemical variation. Within the three subspecies, belli, canescens, and nevadensis, the average percentage of nucleotide difference is 0.1 percent within populations and 0.4 percent between populations within the same subspecies, and 0.6 percent between subspecies (Johnson and Cicero 1991).
Diet and Foraging: Bell's sage sparrows predominantly forage on the ground, mostly by gleaning from the ground and low foliage of shrubs; it rarely catches insects on the wing (Zeiner, et al. 1990). The sage sparrow is categorized as a ground foraging omnivore during the breeding season and a ground gleaning granivore during the nonbreeding period (Martin and Carlson 1998). It feeds mostly on insects, spiders, and seeds while breeding, switching to grasshoppers in the late breeding season (Rotenberry 1980), and mostly on seeds in winter; it also takes green foliage. Apparently, the species drinks regularly (Bent 1968, Smyth and Coulombe 1971). Captives could not survive exclusively on seeds unless supplemented with succulent foods. When water was available, captives drank an average of 49 percent (range 12-99 percent) of body weight daily. It may meet a portion of its water needs from invertebrate foods (Moldenhauer and Wiens 1970).
Daily Activity: A study in Oregon revealed the following breakdown of a sage sparrow's day: 51 percent singing, 35 percent foraging, 12 percent inactivity, 4 percent locomotion and 3 percent aggression (Martin and Carlson 1998). The Bell's sage sparrow exhibits year-long, diurnal activity (Zeiner et al. 1990).
Reproduction: Bell's sage sparrow usually nests in sagebrush or chaparral, and may have two broods per nesting season (Ehrlich, et al. 1988). They prefer to nest in an intermediate sized shrub, 50 to 70 centimeters tall, which may represent a compromise between shrubs that provide favorable foraging sites, avenues of movement, and sufficient cover Martin and Carlson 1998). The subspecies uses a very diverse selection of shrubs including brittlebush (Encelia farinosa), black sage (Salvia mellifera), California buckwheat (Eriogonum fasciculatum), California sagebrush (Artemisia californica), bush mallow (Malocothamnus fasciculatum), chamise (Adenostema fasciculata), white sage (Salvia apiana), valley cholla (Opuntia parryi), ceanothus (Ceanothus sp.), willow (Salix sp.) and bunchgrass species (Martin and Carlson 1998). Individuals remain monogamously pair bonded throughout the year, although partners may change after the breeding season (Martin and Carlson 1998). The nest is a cup of dry twigs and herb stems; it is lined with shreds of bark and grass and contains an inner lining of finer bark fiber, grass, fur, hairs, wool tufts, feathers (Harrison 1978). The nest is located on the ground beneath a shrub; or in a shrub usually 0.15 to 0.45 meters (6-18 inches) above ground, but up to 1 meter (39 inches) in height. It breeds from late March to mid-August with a peak in May and June. The clutch size is 3-5 eggs, usually 3 or 4 eggs. Incubation is typically 13-16 days, and the altricial young fledge in 9-11 days (Harrison 1978, Ehrlich, et al. 1988, Reynolds 1981).
Survival: Sage sparrow populations exhibit substantial yearly fluctuations in population size from unknown causes (30-90 individuals/0.4m2) (Rotenberry 1980, Wiens, et al. 1986, Rotenberry and Wiens 1991). Variations in clutch size have been most strongly correlated with predation; in some cases, predation was by snakes, in other instances by Townsend's ground squirrels (Rotenberry and Wiens 1989).
Dispersal: Young Bell's sage sparrow have been recorded 800 to 900 meters from the nest site by the following spring. Ten hatch-year individuals banded during the breeding season moved 75 to 600 meters by the following spring (Martin and Carlson 1998).
Socio-Spatial Behavior: Male sage sparrows show a strong site tenacity to the breeding territory, even if the habitat is greatly modified (Ehrlich, et al. 1988). In Oregon, Gashwiler (1977) recorded 24-33 pairs per 40 hectares (100 acres). In Nevada, Gustafson (1975) recorded 30 males per 40 hectares (100 acres). Weston and Johnston (1980) reported a density varying from 27-85 individuals per 40 hectares (100 acres) in sagebrush habitat in Mono County. Territory size of the species is highly variable (0.9 to 8.1 acres) depending on local environmental conditions (Reynolds 1981; Rich 1980; Wiens, et al. 1986). For A. belli, the territories in San Diego and Riverside counties varied from 0.75 to 5.7 hectares (Lovio 1993).
Community Relationships: In Nevada, Bond (1940) observed predation by great horned owls. The Bell's sage sparrow is a rare host to cowbird parasitism (Terres 1980).
Long-term fire suppression alters the pattern of natural plant succession and allows communities to reach tall, thick shrublands, probably reducing the availability of sage sparrow habitat for breeding (Martin and Carlson 1998).
Increasing fire frequency in some areas results in the invasion of exotic weeds. With increased fire frequency, native plants are killed and seed reservoirs of grasses and shrubs are depleted and replaced with exotic annuals (Martin and Carlson 1998).
Loss of coastal sage scrub habitat, which includes foraging, roosting and nesting areas, to development activities, fire, and agriculture appear to the primary threats to the Bell's sage sparrow in western Riverside County. Local populations in some areas of southern California have been extirpated as a result of urbanization and agricultural conversion (Barbara Carlson 1998 pers. comm.).
Threats from brood parasitism and predation have not been quantified (Martin and Carlson 1998).
Generally associated with dense stands of chaparral or coastal sage scrub, Bell's sage sparrow is one of the first bird species to return after fires in these preferred habitat areas (B. Carlson 1998 pers. comm.). Sage sparrow populations exhibit substantial yearly fluctuations in population sizes, the cause of which is unknown (30-90 individuals/0.4m2) (Rotenberry 1980, Wiens, et al. 1986, Rotenberry and Wiens 1991). The species also shows differences in their behavior from year to year and from habitat area to habitat area (Wiens et al. 1990).
The territory size of sage sparrows appears to be positively related to coverage of spinescent shrub species and to an index of vegetational horizontal heterogeneity or patchiness, while varying inversely with total vegetation coverage and its horizontal variation and with coverage of grass and sagebrush. Thus, over this range of sites, the sage sparrow territories generally were smaller in areas with more grass and sagebrush and larger in the more heterogeneous areas dominated by spinescent shrubs (Wiens et al. 1985). Territories rapidly expand in size at low densities, with no apparent upper limit. At intermediate to high densities, however, territory size hardly changes with increasing density, suggesting that a minimal acceptable size of territory has been reached and that all usable areas, including suboptimal habitat areas have been occupied (Wiens et al. 1985).
Protective fencing in the Mojave Desert increased abundance and nesting activity of sage sparrows (Brooks 1999). Bolger, et al. (1997) studied the 20-most common bird species within a 260 km2 area of coastal San Diego County in relation to edge/fragmentation sensitivity. Bell's sage sparrow was found to be one of four species whose abundance is most reduced by presence of edges/ fragmentation.
Because of the dense habitat and general tendency of this subspecies to stay below the plant canopy and run behind and beneath bushes, it is more difficult to detect than other subspecies (Bent 1968). Population size estimates may be inaccurate owing to the secretive habits of the species. It moves under cover rapidly when approached and incubating birds rarely leave the nest. However, spring counts to assess population numbers are enhanced by the frequent seasonal vocalizations.
The sage sparrow shows an approximate one year time lag in response to habitat changes. This may be due to the site tenacity of the breeding individuals. Such time lags complicate the attempts to formulate management policies on the basis of short-term before and after surveys. It may be necessary to conduct longer periods of post-treatment studies in order to assess true changes in population sizes (Wiens and Rotenberry 1985). Additionally, territory size did not increase significantly over the short term in areas where vegetation was removed and in fact, territory fidelity or tenacity may be a factor for the first 12 years after vegetation removal (Wiens, et al. 1985). In addition, if insular patches of vegetation are left within territories, sage sparrows may adjust to removal without significant density changes. Where individuals are less abundant, they appear to increase territory size with no apparent upper limit, but do not completely saturate the available habitat (Wiens and Rotenberry 1985).
Fragmentation of shrubland habitats has the potential to affect significantly, the conservation of shrub-obligate species because of the potential permanence of the disturbance (Knick and Rotenberry 1995). Disturbance of shrub habitats in the shrubsteppe regions has the potential to allow invasion of exotic species, including grasses, and increase the fire frequency which then changes the dominance of the shrub areas (Knick and Rotenberry 1995). For the Bell's sage sparrow, the total shrub cover and abundance of shrub species (predominantly sagebrush) are important habitat characteristics. Additionally, the importance of landscape characteristics for the Bell's sage sparrow, especially those relating to fragmentation, have been implicated. The Bell's sage sparrow is more likely to remain in an area that has high shrub cover, low disturbance, combined with large patch size and high within-site spatial similarity. The scale at which species presence is influenced has not been quantified but has been determined to be much larger than the size of an individual's home range (Knick and Rotenberry 1995).
Bent, A.C. 1968. Life histories of North American cardinals, grosbeaks, buntings, towhees, finches, sparrows, and allies. 3 Parts. Edited by O.L. Austin Fr. U.S. Natl.Mus.bull. 237. 1,889 pp.
Bolger, D. T., T. A. Scott and J. T. Rotenberry. 1997. Breeding bird abundance in an urbanizing landscape in coastal Southern California. Conservation Biology 11:406-421.
Bond, R. M. 1940. Food habits of horned owls in the Pahranagat Valley, Nevada. Condor 42:164-165.
Brooks, Matthew. 1999. Effects of protective fencing on birds, lizards, and black-tailed hares in the Western Mojave Desert. Environmental Management 23: 387-400.
Carlson, B. 1998. Pers. Comm.
Ehrlich, R. R., D. S. Dobkin, and D. Wheye. 1988. The Birder's Handbook: A field guide to the natural History of North American Birds. Simon and Schuster, New York.
Garrett, K., and J. Dunn. 1981. Birds of southern California. Los Angeles Audubon Soc. 408pp.
Grinnell, J. and A.H. Miller. 1944. The distribution of the birds of California. Pacific Coast Avifauna 27.
Gashwiler, J. S. 1977. Bird populations in four vegetational types in central Oregon. U.S. Dep. Inter. Fish and Wildl. Serv., Portland OR. Special Tech. Rep. No. 205. 20pp.
Gustafson, J. R. 1975. A sage sparrow egg in a black-throated sparrow nest. Auk 92:805- 806.
Knick, S. T. And J. T. Rotenberry.1995. Landscape characteristics of fragmented shrubsteppe habitats and breeding passerine birds. Conservation Biology 9:1059- 1071.
Harrison, C. 1978. A field guide to the nests, eggs and nestlings of North American birds. W. Collins Sons and Co., Cleveland, OH. 416pp.
Johnson, N. K., and C. Cicero. 1991. Mitochondrian DNA sequence variability in two species of sparrows of the genus Amphispiza. Proc. Inter. Congr. Ornithol. 20: 600-610.
Lovio, J. C. 1993. Diegan coastal sage scrub. I. Breeding bird census. J. Field Ornithol. 64: 95-96.
Martin, John W. and Barbara A. Carlson. 1998. Sage sparrow (Amphispiza belli) In The Birds of North America, No. 326 (A. Poole and F. Gill, eds.) The Birds of North America, Inc., Philadelphia, PA.
McCaskie, G., P. De Benedictis, R. Erickson, and J. Morlan. 1979. Birds of northern California, an annotated field list. 2nd ed. Golden Gate Audubon Soc., Berkeley. 84pp.
Moldenhauer, R. R., and J. A. Wiens. 1970. The water economy of the sage sparrow, Amphispiza belli nevadensis. Condor 72:265-275.
Reynolds, T.D. 1981. Nesting of the sage thrasher, sage sparrow, and Brewer's sparrow in southeastern Idaho. Condor 83: 61-64.
Rich, T. 1980. Territorial behavior of the sage sparrow: spatial and random aspects. Wilson Bulletin 92: 425-438.
Rotenberry, J. T. 1980. Dietary relationships among shrub-steppe passerine birds: competition or opportunism in a variable environment? Ecol. Monogr. 50: 93-110.
Rotenberry, J. T. and J. A. Wiens. 1989. Reproductive biology of shrubsteppe passerine birds: Geographical and temporal variation in clutch size, brood size and fledging success. Condor 91:1-14.
Rotenberry, J.T., and J.A. Wiens. 1991. Weather and reproductive variation in shrub-steppe sparrows: a hierarchical analysis. Ecology 72: 1325-1335.
Smyth, M., and H. M. Coulombe. 1971. Notes on the use of desert springs by birds in California. Condor 73:240-243.
Terres, J. K. 1980. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf, New York, New York. 1109pp.
Weston, H. G., Jr., and D. Johnston. 1980. Summer and fall censusing of bird populations in the Bodie/Coleville region. Harvey and Stanley Assoc., Alviso, CA. Rep. To U. S. Dep. Inter. Bur. Land Manage., Bakersfield CA Contract No. CA-01.
Wiens, J.A. and J.T. Rotenberry. 1981. Habitat associations and community structure of birds in shrubsteppe environments. Ecological Monographs 51: 21-41.
Wiens, J.A. and J.T. Rotenberry. 1985. Response of breeding passerine birds to rangeland alteration in a North American shrubsteppe locality. J. Applied Ecology 22: 655-668.
Wiens, J.A. and J.T. Rotenberry, and B. Van Horne. 1985. Territory size variation in shrubsteppe birds. Auk 102: 500-505.
Wiens, J.A., J.T. Rotenberry, and B. Van Horne. 1986. A lesson in the limitations of field experiments: shrub-steppe birds and habitat alteration. Ecology 67: 365-376.
Wiens, J. A., B. Van Horne, and J. T. Rotenberry. 1990. Comparisons of the behavior of sage and Brewer's sparrows in shrubsteppe habitats. Condor 92: 264-266.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
black-crowned night heron (Nycticorax nycticorax) (Breeding Rookeries)
State: None
Federal: None
The black-crowned night heron is relatively well-distributed throughout the MSHCP Plan Area within its suitable habitat; however, it is not predictably distributed within all suitable areas. It occurs at almost all of the open water bodies where emergent or riparian vegetation is present and many of the playas and riparian drainages that may provide foraging opportunities. There are several Core Areas for this species, including Mystic Lake/San Jacinto Wildlife Area, Prado Basin/Santa Ana River, and Collier Marsh. The breeding locations, which have been documented as active or historic, are located at specific sites that require conservation. Because it is well known for using emergent habitat, riparian areas for breeding, and ponds and other aquatic habitat for foraging, but has specific locations that are used for breeding, it is assumed that this species will respond to a landscape level of management with site-specific requirements (e.g., breeding rookeries).
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 16,560 acres of suitable nesting and foraging habitat for the black-crowned night heron including freshwater marsh, playas and vernal pools, riparian scrub, woodland, and forest, and cismontane alkali marsh.
Include within the MSHCP Conservation Area at least the 3 known and historic breeding locations in the Prado Basin/Santa Ana River (9,670 acres), Mystic Lake/San Jacinto Wildlife Area (Subunit 4 of Reche Canyon/Badlands Area Plan; 2,690 acres), and Collier Marsh areas (Proposed Linkage 2; 160 acres).
A 100-meter buffer will be established around the Core Areas identified in Objective 2 as they are incorporated into the MSHCP Conservation Area.
The black-crowned night-heron is virtually restricted to more aquatic wetlands for foraging but may use more forested riparian areas for nesting (Garrett and Dunn 1988). Because they will use a relatively wide variety of wetlands for various parts of their life history, a wide range of habitats has been included for this analysis. For the purpose of the conservation analysis, potential habitat for the black-crowned night-heron has been separated into the primary breeding habitat which includes freshwater marsh and riparian scrub, forest, and woodland. The secondary habitat, which is composed only of foraging habitat includes playas and vernal pools and cismontane alkali marsh. Based on these habitats, the Plan Area supports approximately 20,560 acres of potential habitat for the black-crowned night-heron composed of 12,680 acres of primary breeding and foraging habitat and 7,880 acres of secondary foraging habitat. Table 1 shows the conservation of potential habitat for the black-crowned night-heron. Overall, approximately 9,840 acres (78 percent) of potential primary breeding and foraging habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public Lands. Approximately 6,720 acres (86 percent) of secondary foraging habitat will be conserved in Criteria Area or existing Public/Quasi-Public lands.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
BLACK-CROWNED NIGHT-HERON
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Riverside Lowlands and San Jacinto Foothills Bioregions | |||||||
| Primary Habitat for Breeding and Foraging | |||||||
| Freshwater Marsh | 470 | 170 | 240 | 410 | 0 | 60 | 60 |
| Riparian Scrub, Woodland, Forest | 12,210 | 3,570 | 5,860 | 9,430 | 180 | 2,600 | 2,780 |
| Subtotal Primary Habitat | 12,680 | 3740 (30%) |
6100 (48%) |
9840 (78%) |
180 (1%) |
2660 (21%) |
2840 (22%) |
| Secondary Habitat for Foraging | |||||||
| Playas and Vernal Pools | 7,870 | 3,830 | 2,880 | 6,710 | 0 | 1,160 | 1,160 |
| Cismontane Alkali Marsh | 10 | 10 | 0 | 10 | 0 | 0 | 0 |
| Subtotal Secondary Habitat | 7,880 | 3,840 (49%) |
2,880 (37%) |
6,720 (86%) |
0 (0%) |
1,160 (14%) |
1,160 (14%) |
| TOTAL | 20,560 | 7,580 (37%) |
8,980 (44%) |
16,560 (81%) |
180 (1%) |
3,820 (18%) |
4,000 (19%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
In addition, the Riparian/Riverine Areas and Vernal Pools policy described in Section 6.1.2 of the MSHCP, Volume I, provides for conservation of wetlands, which provide habitat for this species, through avoidance and minimization. Mitigation for impacts to wetlands shall be incorporated in accordance with the "No Net Loss" policy of federal and state wetland regulations. The proposed mitigation shall be directly related to the functions and values of the wetland as related to this species and result in equivalent replacement.
As described below under Data Characterization, 29 of the 69 recent point localities have a high location precision. Of these 29 point localities, 5 will be inside the Criteria Area and 5 will be inside the Public/Quasi-Public Lands. In addition, the one known nesting colony location and the potential or historical nesting locations are within the Criteria Area or Public/Quasi-Public Lands. A total of 17 point localities will be outside of the MSHCP Conservation Area. However, these locations, if within a wetland area, will continue to receive protection by the wetland policy. Conservation of this species can be considered from a landscape perspective because the species has well identified habitat requirements.
In addition, there are definable locations composed of Core Areas for focusing conservation efforts which are included within the MSHCP Conservation Area. These conserved Core Areas include the 3 known and historic breeding locations in the Prado Basin/Santa Ana River (9,670 acres), Mystic Lake/San Jacinto Wildlife Area (Subunit 4 of Reche Canyon/Badlands Area Plan; 2,690 acres), and Collier Marsh areas (Proposed Linkage 2; 160 acres). The Core Area at Prado Basin/Santa Ana River includes the only known nesting colony for the black-crowned night-heron and the Core Area at Mystic Lake/San Jacinto Wildlife Area is an historic or potential breeding location. A total of 12,520 acres of Core Areas are conserved within the MSHCP Conservation Area. Additionally, as part of the reserve assembly, a 100-meter buffer will be established around the Core Areas identified above as they are incorporated into the MSHCP Conservation Area.
Several large blocks of habitat including potential or historic foraging and nesting areas for the black-crowned night-heron will be conserved as Criteria Area and Public/Quasi-Public Lands including the Prado Basin/Santa Ana River, Lake Skinner, Diamond Valley Lake, Lake Mathews, Mystic Lake, San Jacinto Wildlife Area/Mystic Lake, Lake Perris, Wasson Canyon, Temecula and Murrieta creeks, San Timoteo Creek, Temescal Wash, Lake Elsinore, and Vail Lake. The MSHCP Conservation Area will provide adequate habitat for foraging during nomadic visits to the area and migratory stopovers as well as habitat containing potential nest sites with adequate protection around each nest site and foraging areas during the breeding season. Foraging areas are provided at Vail Lake, Lake Skinner, Diamond Valley Lake, San Jacinto Wildlife Area/Mystic Lake, Lake Perris, Lake Elsinore, Lake Mathews, Prado Basin and Santa Ana River, and a variety of other smaller riparian and wetland areas. Potential and known nest sites are provided in the San Jacinto Wildlife Area/Mystic Lake, Collier Marsh, and Prado Basin and foraging for a potential breeding season is provided in the riparian and marsh areas within and around Collier Marsh, within the Santa Ana River system and along the San Jacinto River near the San Jacinto Wildlife Area and Mystic Lake. These MSHCP Conservation Area locations are interconnected as well, though the ability of this species to move long distances may reduce the importance of these linkages for this species.
In summary, conservation for this species will be achieved by inclusion of at least 16,560 acres of suitable Conserved Habitat including 9840 acres of primary breeding and foraging habitat and 6,720 acres of secondary foraging habitat. Additionally, the three core known or potential breeding locations, Prado Basin/Santa Ana River, Collier Marsh, and Mystic Lake/San Jacinto Wildlife Area within large blocks of habitat are included in the MSHCP Conservation Area. As these Core Areas are incorporated into the MSHCP Conservation Area, a 100-meter buffer will be established around each Core Areas. The current population size of the black-crowned night-heron is unknown.
The Incidental Take of the black-crowned night-heron is difficult to quantify at this time owing to our limited knowledge of the precise location and extent of nesting sites and the fact that losses may be masked by fluctuations in abundance and distribution during the life of the permit. However, the level of Take of black-crowned night-heron can be anticipated by the loss of the number of acres of habitat that will be impacted or become unsuitable for this species. About 2,840 acres (22 percent) of potential primary breeding and foraging habitat for the black-crowned night-heron will be outside the Criteria Area and Public/Quasi-Public Lands. Approximately 1,160 acres (14 percent) of potential secondary foraging habitat for the black-crowned night-heron will be outside the Criteria Area and Public/Quasi-Public Lands.
This comprises approximately 19 percent of the total potential habitat. No Take of nesting colonies will occur. The estimate of Incidental Take is consistent with the anticipated land uses and the application of the riparian/riverine area and vernal pool avoidance and land use adjacency policies/guidelines.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The UCR location database includes approximately 79 records for the black-crowned night-heron within the Plan Area dated from 1900 to 2000. A total of approximately 69 records are relatively recent (dated since 1990) and of these recent records, 29 are high precision records that can be accurately placed within the area. The habitat types associated with these recent and high precision data records include riparian, agriculture, alluvial, grassland, alkali playa, open water, sage scrub, and residential. The residential habitat records may reflect records that are either no longer extant or where the location is a small pocket of suitable habitat within or adjacent to a developed area. The upland records or records in habitat that is not suitable may also be records of the species observed in a small pocket of suitable habitat that is adjacent to the upland habitat. Breeding locations have not been recorded specifically within the database but have been documented from other sources as identified below.
Black-crowned night-herons require marshes, ponds, reservoirs, and estuaries for foraging and also occur along the margins of lacustrine, large riverine, and fresh and saline emergent habitats and, rarely, in kelp beds in marine subtidal habitats (Garrett and Dunn 1981; Gallagher 1997). Its habitat requirements are varied, including all types of wetland areas including swamps, streams, rivers, margins of pools, ponds, lakes, lagoons, tidal mudflats, fresh, brackish, and salt water ecosytems and even using man-made ditches, canals, reservoirs, and wet agricultural fields (Davis 1993). In inland areas, most colones are associated with large wetlands. These wetland areas, if they rely on rainfall, may have varying water levels. Therefore, black-crowned night-herons may fluctuate in their usage of such inland areas (Davis 1993). It nests and roosts in dense-foliaged trees, not always near water, and in dense, fresh or brackish emergent wetlands (Grinnell and Miller 1944). As might be expected of a widely distributed, opportunistic forager, these birds use a broad spectrum of habitat types for nesting, and choose nest sites from ground to 160 feet in height (Palmer 1962). Most colony sites are on islands, in swamps, or over water, suggesting that site selection may be related to predator avoidance. The variety of substrates used for nesting is enormous including oak trees, willow trees, poison ivy, box elder trees, cattails, and areas level with the water surface supported by floating dead vegetation (Davis 1993). It often rests on piers and pilings (Zeiner, et al. 1990).
Black-crowned night-herons breed in the western hemisphere from British Columbia eastward to Nova Scotia southward locally through the Americas to southern South America. The species winters locally from Washington to New England southward throughout the remainder of the breeding range (AOU 1998). The distribution of the species is generally determined by the suitable wetland habitat for feeding. The colonies are locally distributed within this range and they often occur on islands (Davis 1993).
Hunting, disturbance at breeding colonies, drainage of wetlands, and land development for homes and recreation have caused declines in heron numbers (Gross 1923; Davis 1993). DDT and other pesticides are thought to have caused local reproductive failure and population declines but convincing documentation is lacking and sparse census data from the early 20th century makes trend analysis difficult (Davis 1993).
Zeiner, et al. (1990) summarize the distribution, abundance, and seasonality of the black-crowned night-heron within California as follows. The black-crowned night-heron is a fairly common, year-long resident in lowlands and foothills throughout most of California, including the Salton Sea and Colorado River areas, and very common locally in large nesting colonies. It is a common nesting species on the northeastern plateau of California from April to August. It is uncommon in the northwestern part of the state, and rare in northeastern California in midwinter. It is an uncommon transient and rare species in winter in the southern deserts, and rare on the Channel Islands. It is seldom seen in the mountains, but formerly nested at Big Bear Lake in San Bernardino Mts. (Cogswell 1977, McCaskie, et al. 1979, Garrett and Dunn 1981). In southern California, the species generally occurs locally throughout as a year round resident except for mountainous and desert areas (Garrett and Dunn 1981). Rookeries are scarce within southern California. It is a local migrator, dispersing widely from breeding colonies after nesting (Gill and Mewaldt 1979). Much of the breeding population from northwestern and northeastern California probably moves southward and is absent from those areas in midwinter.
The black-crowned night-heron may be found throughout the Plan Area in appropriate habitat within Riverside lowland and San Jacinto Foothills Bioregions. The only known recently active rookery in western Riverside County is in the Prado Basin (Patten 1998, pers. comm.) . However, there was no direct evidence of nesting in the Prado Basin in recent years (Pike, 2001, pers. comm.). Additional potential locations include Collier Marsh, Mystic Lake/San Jacinto Wildlife Area (the species formerly bred at this locale [Garrett and Dunn 1981]), Lake Mathews, Vail Lake, Lake Perris, and Lake Skinner.
Other geographic locations recorded within the U.C. Riverside database include: Santa Ana River, Temescal Wash, Cajalco Creek, Woodcrest, Moreno Valley, Lake Perris, San Timoteo Creek, San Jacinto River, Winchester, Canyon Lake, Temecula Creek, and Lake Skinner.
Genetics: Sheldon's (1987) DNA-DNA hybridization work on the phylogeny of herons generally supports a linear arrangement of herons beginning with day and night herons and ending with tiger herons and bitterns, but suggests that no great genetic distinction exists between the day and night herons. It is concluded that the yellow-crowned and black-crowned night-herons are as divergent genetically from each other as either is from most day herons.
Diet and Foraging: The black-crowned night-heron feeds along the margins of lacustrine, large riverine, and fresh and saline emergent habitats and rarely on kelp beds in marine subtidal habitats. It prefers shallow, weedy pond margins, creeks, and marshes (Davis 1993). One study listed the following food items found in regurgitated samples: annelids, insects, crustaceans, amphibians and fishes, with fishes being dominant (Sodhi 1992). Other investigators have described the diet as: a highly variable diet consisting of fishes, crustaceans, aquatic insects and other invertebrates, amphibians, reptiles, small mammals, and rarely young birds (Palmer 1962, Wolford and Boag 1971b). Collins (1970) and Hunter and Morris (1976) reported observing the species feeding on young terns. It usually hunts in shallow water, waiting motionlessly or, less commonly, stalking its prey slowly (Kushlan 1976a). Sometimes it vibrates its bill to lure or flush prey, and it may alight briefly on deep water to make a strike.
Daily Activity: The black-crowned night-heron feeds mostly nocturnally and crepuscularly and sometimes also feeds diurnally (Zeiner, et al. 1990; Terres 1980). It generally feeds throughout the night, avoiding competition with day herons which use the same habitat (Kushlan 1973).
Reproduction: Nests of the black-crowned night-heron are located in dense-foliaged trees, dense, fresh or brackish emergent wetlands, or dense shrubbery or vine tangles, usually near aquatic or emergent feeding areas. The nests are built of twigs and/or marsh plants (Zeiner, et al. 1990). The nest is usually a platform of sticks of whatever trees or vegetation is available. As an example, they may use box elder, cedar, oak, pine, bayberry, plum, and cattails (Davis 1993). Some nests are sturdy, others are flimsy and the eggs are visible from below. Nest-sites are usually near aquatic or emergent feeding areas, but the non-breeding-season roosts may be farther away. Nests can be near tree trunks or distal forks of branches, in the open or deep in the foliage (Davis 1993). Beaver et al. (1980) gives the average nest heights and standard deviations for colonies as 2.6 meters + 0.93.
The species breeds mainly February to July, but also April to August in northeastern California (Cogswell 1977). It is a monogamous, colonial nester. The clutch size is 3-4 eggs, sometimes 5 eggs. The mean clutch size for 684 nests in a South San Francisco Bay colony (Bair Island) in May 1971, was 2.9 eggs (Gill 1977). Incubation is reportedly 24-26 days. The semi-altricial, downy young are tended by both parents. They fly first at six weeks, but are not independent until some time later. A few breed at 1 year, but most do not breed until 2-3 years of age (Palmer 1962, Harrison 1978).
Survival: The nesting success of the black-crowned night-heronis mainly affected by avian predation for a current population in Oregon and Washington (Blus, et al. 1997). Survival rates measured for chicks in coastal Virginia were between 0.90 and 1.00 during the first two weeks of life and between 0.25 and 0.60 during the next 40 to 55 days when birds have left their birth colony (Erwin, et al. 1996). There are banding recoveries for birds aged 15 years to 21 years (Davis 1993).
Dispersal: Many year-old black-crowned night-herons return to the vicinity of their natal colony, but many are widely dispersed and may end up thousands of miles from the natal area. The juvenile birds disperse widely in all directions after nesting but make relatively restricted movements thereafter (Davis 1993, Erwin et al. 1996).
Socio-Spatial Behavior: The black-crowned night-heron occurs in large nesting colonies. Individuals can be relatively social during their foraging activity. In North Carolina they may forage up to 8 kilometers (5 miles) from the nesting area (Custer and Osborn 1978). The breeding territory, used for courtship, copulation, and nesting, is large initially, but shrinks after pair-formation to a few feet around the nest (Palmer 1962). Sometimes the species defends roosting and feeding territories (Palmer 1962).
Community Relationships: Corvidae and other predators eat the eggs of black-crowned night-herons (Zeiner, et al. 1990). The black-crowned night-heron is gregarious at all seasons. It may nest in the same tree with most North American day herons and several species of ibises. It occurs in communal roosts in winter. It is usually a solitary forager and often is supplanted or driven off by day herons during the breeding season (Davis 1993).
Grinnell and Miller (1944) reported that whereas the black-crowned night-heron was formerly abundant within the State of California, it was by then greatly depleted locally. Although habitat destruction and persecution (Gallagher 1997) are implicated in the species' decline, environmental contaminants and disease may also be problematical, as is evidenced by recent, massive die-offs of water-associated species at the Salton Sea (USFWS, 1999, unpublished data).
Human disturbance of nesting colonies in Quebec (simulating a typical scientific nesting study) resulted in nest abandonment, predation of eggs, and reduced late-season nesting (Tremblay and Ellison 1979). Numbers have been reduced from the drainage of marshes and swamps, and cutting of trees, but this species is more adaptable and persistent than most other herons, bitterns, and egrets (Davis 1993).
The black-crowned night-heron rookery in the Prado Basin apparently is one of few undisturbed colonies in coastal southern California, although nesting was not confirmed for the 2001 breeding season. For instance, several potential breeding records in Orange County came to light during the breeding bird atlas effort there because citizens reported the felling of trees supporting heron nests which then destroyed the colony (Gallagher 1997).
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Beaver, D. L., R. G. Osborn, and T. W. Custer. 1980. Nest-site and colony characteristics of wading birds in selected Atlantic coast colonies. Wilson Bull. 92: 200-220.
Blus, L. J., B. A. Rattner, M. J. Melancon, and C. J. Henny. 1997. Reproduction of black-crowned night-herons related to predation and contaminants in Oregon and Washington, USA. Colonial Waterbirds 20:185-197.
Cogswell, H. L. 1977. Water birds of California. Univ. California Press, Berkeley. 399pp
Collins, C. T. 1970. The black-crowned night heron as a predator of tern chicks. Auk 87:584-586.
Custer, T. W., and R. G. Osborn. 1978. Feeding habitat use by colonially-breeding herons, egrets, and ibises in North Carolina. Auk 95:733-743.
Davis, W. E. Jr. 1993. Black-crowned night-heron (Nycticorax nycticorax). In The Birds of North America, No. 205 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, and The American Ornithologists' Union, Washington, D.C.
Erwin, R. M., J. G. Haig, D. B. Stotts and J. S. Hatfield. 1996. Reproductive success, growth and survival of black-crowned night-heron (Nycticorax nycticorax) and snowy egret (Egretta thula) chicks in coastal Virginia. Auk 113:119-130.
Erwin, R.M., J.G. Haig, D.B. Stotts, and J.S. Hatfield. 1996. Dispersal and habitat use by post-fledging juvenile snowy egrets and black-crowned night herons. Wilson Bulletin 108:342-356.
Erwin, R. M., J. S. Hatfield, and W. A. Link. 1991. Social foraging and feeding environment of the black-crowned night-heron in an industrialized estuary. Bird Behaviour 9:94:102.
Gallagher, S. 1997. Breeding Bird Atlas (Orange County). Sea and Sage Audubon Press, Santa Ana, California. 264 pp.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Gill, R. E., Jr. 1977. Breeding avifauna of the South San Francisco Bay estuary. West. Birds 8:1-12.
Gill, R. E., Jr., and L. R. Mewaldt. 1979. Dispersal and migratory patterns of San Francisco Bay produced herons, egrets, and terns. North Am. Bird Bander 4:4-13.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Copper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April 1986. 617 pp.
Gross, A. O. 1923. The black-crowned night heron of Sandy Neck. Auk 40: 1-30.
Harrison, C. 1978. A field guide to the nests, eggs and nestlings of North American birds. W. Collins Sons and Co., Cleveland, OH. 416pp.
Hunter, R. A., and R. D. Morris. 1976. Nocturnal predation by a black-crowned night heron at a common tern colony. Auk 93:629-632.
Kushlan, J. A. 1973. Black-crowned night-heron diving for prey. Fla. Field Nat. 1: 27-28.
Kushlan, J. A. 1976. Feeding behavior of North American herons. Auk 93:86-94.
Landin, M. C. and R. F. Soots. 1977. Colonial bird use of dredged material islands: a national perspective. Proc. Colon. Waterbird Group 1977: 62-72.
McCaskie, G., P. De Benedictis, R. Erickson, and J. Morlan. 1979. Birds of northern California, an annotated field list. 2nd ed. Golden Gate Audubon Soc., Berkeley. 84pp.
Palmer, R. S., ed. 1962. Handbook of North American birds. Vol. 1. Yale University Press, New Haven, CT. 567pp.
Patten, M. 1998. Riverside County Editor for American Field Notes and Past Secretary, California Bird Records Committee, pers. comm.
Pike, J. 2001. USFWS Volunteer Field Biologist, pers. comm.
Sheldon, F. H. 1987. Phylogeny of herons estimated from DNA-DNA hybridization data. Auk 104: 970108.
Sodhi, N. S. 1992. Food of black-crowned night-heron nestlings. Pavo 23:47-52.
Terres, J. K. 1980. The Audubon Society Encyclopedia of North American birds. A. Knopf, New York. 1100pp.
Tremblay, J., and L. N. Ellison. 1979. Effects of human disturbance on breeding of black- crowned night herons. Auk 96:364-369.
USFWS, 1999, unpublished data.
Wolford, J. W., and D. A. Boag. 1971a. Distribution and biology of black-crowned night herons in Alberta. Can. Field-Nat. 85:13-19.
Wolford, J. W., and D. A. Boag. 1971b. Food habits of black-crowned night herons in southern Alberta. Auk 88:435-437.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
black swift (Cypseloides niger) - breeding
State: Species of Special Concern
Federal: Partners in Flight Watch List; Fish and Wildlife Service Migratory Nongame Birds of Management; San Bernardino National Forest Sensitive
The black swift has been recorded in very low numbers spread widely over the Plan Area. Almost all of the observations are of migrating individuals except for the vicinity of the known nesting location in the San Jacinto Mountains. It will forage on the wing in every habitat available within the Plan Area. It has very specialized nest site requirements that only occur in one or possibly two locations within the Plan Area both of which are located within the San Bernardino National Forest. For foraging purposes, it can be managed on a landscape level.
The black swift is designated as a Forest Service Sensitive Species. Forest Service Sensitive Species are protected through the implementation of Forest plans and the biological evaluation (BE) process, which considers the potential effects of Forest Service activities on these species.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation area at least 34,020 acres of deciduous woodland and forest and montane coniferous forest within the San Bernardino Mountains and San Jacinto Mountains Bioregions to provide breeding and foraging habitat, including the known nesting location of the black swift at Tahquitz Creek within the San Jacinto Wilderness Area and the potential nesting location at the north fork of the San Jacinto River in the San Jacinto Mountains.
For the purpose of the conservation analysis, habitats for the black swift include montane coniferous woodland and deciduous woodland and forest habitats of the San Jacinto Mountains and San Bernardino Bioregions that contain mountainous waterfalls and cliffs required for nesting and roosting. One black swift nest site and another potential nest site have been documented within the habitat and the area is likely to contain additional cliffs suitable for nesting and roosting. Based on these habitats, the Plan Area supports approximately 46,290 acres of potential habitat for the black swift. Table 1 shows the conservation and loss of potential habitat for the black swift. Overall, approximately 34,020 acres (73 percent) of potential habitat will be conserved in the Criteria Area or existing Public/Quasi-Public lands.
The one known nest location at the falls on Tahquitz Creek, and a potential nest site on the north fork of the San Jacinto River, will be conserved within Public/Quasi-Public Lands. Other likely nest locations within cliff areas are generally located within The San Jacinto Wilderness Area, which will be conserved.
The MSHCP indicates that the black swift will be conserved at the landscape level. Conserving large blocks of suitable habitat within the area of known occurrences and nest site locations will capture additional localities of the black swift. The U.S. Forest Service will need to manage known and potential nest sites as well as maintain the condition of the waterfalls within the drainages where nesting may occur. Additionally, since waterfalls are also popular recreation sites, the U.S. Forest Service management attention is needed to ensure that black swift nest sites are not disturbed (Stephenson and Calcarone 1999).
TABLE 1
SUMMARY OF HABITAT CONSERVATION
BLACK SWIFT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| San Jacinto Mountains and San Bernardino Mountains Bioregions | |||||||
| Deciduous Woodlands and Forests | 16,490 | 300 | 13,320 | 13,620 | 850 | 2,020 | 2,870 |
| Montane Coniferous Forest | 29,800 | 20 | 20,380 | 20,400 | 40 | 9,360 | 9,400 |
| TOTAL | 46,290 | 320 (<1%) |
33,700 (73%) |
34,020 (73%) |
890 (2%) |
11,380 (25%) |
12,270 (27%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Several large blocks of habitat supporting the known and potential foraging and nesting locations of the black swift will be conserved within the Criteria Area and Public/Quasi-Public lands, including deciduous and coniferous woodland habitat within the San Jacinto Mountains and San Bernardino Mountains Bioregions. Good dispersal and foraging capabilities allow the black swift to use foraging and migration habitat throughout the MSHCP Plan Area. As such, the MSHCP Conservation area will provide adequate foraging and migration areas for this species.
In summary, conservation for this species will be achieved by inclusion of at least 34,020 acres of suitable Conserved Habitat, including montane coniferous woodland and deciduous woodland and forest habitats of the San Jacinto Mountains and San Bernardino Bioregions. In addition, the one known and one potential nest site will be conserved in the MSHCP Conservation Area. The current population size of the black swift within the Plan Area is unknown.
The Incidental Take of the black swift is difficult to quantify due to our limited knowledge of its distribution and abundance within the Plan Area. The maximum level of Incidental Take of black swift can be anticipated by the loss of the number of acres of habitat. Approximately 12,270 acres (27 percent) of potential habitat for the black swift will be outside the Criteria Area and Public/Quasi-Public Land designations and individuals within this area will be subject to Incidental Take consistent with the Plan. No known nesting locations will be subject to Take.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The location database for the black swift includes nine records dated from 1897 to 1999. The older records (1959 and earlier) are likely from museum records or skins and all but two of the records are lacking precision to be able to locate the record accurately. Two records, from 1995 and 1999, are of high precision and documented to occur within riparian and oak woodland habitat and likely accurately reflect the low population numbers within the Plan Area. These two records are of foraging individuals and probably were recorded during migration.
Little literature is available for the black swift probably due to its low population size. Most of the available information is relatively old or is very general in nature and descriptive of the natural history of the species. There are no controlled scientific studies that have been conducted and little management information is available. Very little information is available for the Plan Area other than what is available regarding basic distribution information.
The black swift is observed flying high over western mountains and canyons and thus is not documented as being present very often. If there are suitable nest sites for breeding, the black swift will forage over almost any terrain and habitat (Lack 1956). It nests in moist crevices or caves on sea cliffs above the surf, or on cliffs behind, or adjacent to, waterfalls in deep canyons (Lack 1956). It forages widely over many habitats. It lives where there are rocky cliffs available for its somewhat specialized nest site but has great powers of flight and often ranges far away from the nesting area. It generally requires coastal or mountain cliffs (Terres 1980). Habitats that are used by the black swift in the Sierra Nevada include montane hardwood conifer forest, mixed conifer, Jeffrey pine forest, red fir, lodgepole pine forest, montane riparian habitat, barren habitat, and douglas fir forest (DeSante 1999).
It breeds from southeastern Alaska, British Columbia, western Washington, Montana, south to the Rocky Mountain States, New Mexico, Nevada and to southern California, south to Costa Rica and the West Indies. Its winter range is not precisely known but it includes tropical America. The areas where it occurs in highest abundance are the Pacific Northwest regions and coastal British Columbia (Terres 1980). Black swifts tend to be more common along the west coast states from Mexico north into Canada. Their range extends into Arizona and Colorado.
The black swift breeds very locally in the Sierra Nevada and Cascade Range, the San Gabriel, San Bernardino, and San Jacinto Mountains, and in coastal bluffs and mountains from San Mateo County south probably to San Luis Obispo County. It seems to avoid arid regions, however, such as the Great Basin, southern deserts, and Central Valley. In migration, it is rare and irregular outside the breeding range and does not winter in the state (Grinnell and Miller 1944, Remsen 1978, McCaskie, et al. 1979, McCaskie et al. 1988, Garrett and Dunn 1981). The black swift migrates south for the winter and is mostly absent from October through April. It is noted rarely and irregularly outside the breeding range, mostly west of the Great Basin and southern deserts (Knorr 1961).
The black swift is present within western Riverside County as a breeding bird in the San Bernardino and San Jacinto Mountains (Zeiner, et al. 1990). It is documented as breeding at Tahquitz Creek and probably the north fork of the San Jacinto River in the San Jacinto Mountains (Garrett and Dunn 1981). Although recorded in other parts of the Plan Area, these location records are probably of migrant individuals which occur within the area on an irregular basis. It has been documented in the literature to occur in other parts of the Plan Area as an irregular transient (Garrett and Dunn 1981).
Genetics: The groupings of the species within each genera of the swift family are based on the stiffening of the rectrices and the presence or absence of spiny tips on the tail feathers (Lack 1956). The black swift is different from other congeners due to its normal tail feathers without spiny tips. All the rest of the congeners have rectrices somewhat stiffened with slightly projecting bare tips. However, with the dark plumage of C. niger and its nesting habits, it is in close relationship with the rest of the Cypseloides (Lack 1956).
Diet and Foraging: The black swift feeds exclusively on flying insects, captured in sustained, long-distance foraging flights, usually high in the air. It often pursues insects in updrafts associated with cliffs or storm fronts (Udvardy 1954). Winged ants comprise 91 percent of the prey items provided to the nestlings (Marin 1999). Other food items include caddis flies, mayflies, crane flies, flesh flies, midges, beetles, termites, aphids, bees, wasps, and spiders (Terres 1980).
Daily Activity: The black swift exhibits diurnal activity, including during migration (Zeiner et al. 1990). Other swifts undergo periods of torpor in cold weather, when flying insects are scarce (Terres 1980), and the black swift may do the same. Apparently the only regular resting or roosting places are on steep, rocky, often moist, cliffs, such as those used for nesting (Bent 1940).
Reproduction: The black swift builds its nest in moist locations, usually associated with water, on a sea cliff above the surf, or on the cliff behind, or adjacent to a waterfall in a deep canyon (Lack 1956; Marin 1997). The nest location must provide complete protection from rain, wind and sunshine and tends to be located on inaccessible cliffs at isolated locations (Michael 1927). The nest is constructed of mud mixed with moss, ferns, seaweed, or other plant materials; it is located in a deep, dark crevice, in a cave, or under an overhang (Bent 1940). It nests in a colony of a few pairs; six nests were observed at a location in Yosemite (Lack 1956; Michael 1927). The nest is usually kept moist by mist from the surf or waterfall (Lack 1956). The breeding season lasts from early June to late August with the peak egg-laying period in mid-June (Lack 1956; Marin 1999). It lays only 1 large egg per year (Harrison 1978; Marin 1997; Knorr 1961). Incubation lasts 24-27 days. The altricial young leave the nest at about 45 days (Hunter and Baldwin 1962), but the nestling period is probably highly variable as in other swifts (Lack 1956). The young can go without food for long periods (Terres 1980).
Survival: No information is available in the literature.
Dispersal: Summer movements of the black swift may be of great distances extending to areas several hundred or even more than a thousand miles from the breeding localities and that distance is easily flown in two or three days. These movements appear to be related to weather conditions and seasonal cyclones (Udvardy 1954).
Socio-Spatial Behavior: The home range of the black swift is very large, but has not been measured (Bent 1940, Grinnell and Miller 1944). Territoriality has not been reported for this species. The territory is presumably limited to the nest site (Zeiner, et al. 1990).
Community Relationships: Nests of the black swift are inaccessible to terrestrial predators and human disturbance, with the exception of rock climbers, who rarely use these wet cliffs (Zeiner, et al. 1990).
No information is available in the literature. Potential threats to the species may be related to the relatively narrow requirements for the nesting location (see below) and the relatively few situations available within the range of the species that satisfy these requirements.
Conflicts related to nesting black swifts could include rock climbing, spelunking, mining, road construction, hiking, bicycling, horseback trails, water diversions, and housing developments. Probably the greatest disturbance to the black swift nesting habitat is hiking trails to the base or top of waterfalls and any rock or ice climbing. The effect that ice climbing may have on nesting habitat needs research. Rock climbing can remove lichens, mosses and other hydrophilic plants needed in the building of nests, and climbing at waterfalls could disturb incubation, brooding, and foraging of swifts (Colorado Partners in Flight 2000).
Five ecological features seem to be of importance for the presence of black swifts within an area within their range: the presence of water, high relief as regards the configuration of the terrain, inaccessibility, darkness, and the lack of flyway obstructions (Knorr 1961). The discussion of these ecological requirements is as follows (Knorr 1961). Without exception, water is present at every nesting site, varying in degree from a rushing torrent to a mere trickle, although the former seems to be preferred. There appears to be a requirement that the nesting site have a commanding position above the surrounding terrain so that birds flying out from the nest on a horizontal course find themselves automatically at feeding altitude above the adjacent valley. The requirement that a black swift nest be inaccessible to terrestrial predators appears to be inflexible. No nest has been found which was accessible to anything without wings. It appears that the gloom of the innermost recesses in the rock is preferred to lighter situations and it has been observed that the sun rarely shines on the nest. In conjunction with the requirement of high relief, the air immediately in front of a nesting site must be free of obstructions such as trees or tree branches.
Bent, A. C. 1940. Life histories of North American cuckoos, goatsuckers, hummingbirds, and their allies. U.S. Natl. Mus. Bull. 176. 506pp.
Colorada Partners in Flight. 2000. Physiographic Region 62:Southern Rocky Mountains.
DeSante, D. 1999. Species Accounts of the Sierra Nevada Bird Conservation Plan. www.prbo.org CPIF/Sierra.
Garrett, K., and J. Dunn. 1981. Birds of southern California. Los Angeles Audubon Soc. 408pp.
Grinnell, J., and A. H. Miller. 1944. The distribution of the birds of California. Pac. Coast Avifauna No. 27. 608pp.
Harrison, C. 1978. A field guide to the nests, eggs and nestlings of North American birds. W. Collins Sons and Co., Cleveland, OH. 416pp.
Hunter, W. F., and P. H. Baldwin. 1962. Nesting of the black swift in Montana. Wilson Bull. 74:409-416.
Knorr, O. A. 1961. The geographical and ecological distribution of the black swift in Colorado. Wilson Bull. 73:155-170.
Lack, D. 1956. A review of the genera and nesting habits of swifts. Auk 73:1-32.
Marin, M. 1997. Some aspects of the breeding biology of the black swift. Wilson Bulletin. 109: 290-306.
Marin. M. 1999. Food, foraging and timing of breeding of the black swift in California. Wilson Bulletin 111: 30-37.
McCaskie, G., P. De Benedictis, R. Erickson, and J. Morlan. 1979. Birds of northern California, an annotated field list. 2nd ed. Golden Gate Audubon Soc., Berkeley. 84pp.
McCaskie, G., P. De Benedictis, R. Erickson, and J. Morlan. 1988. Birds of northern California, an annotated field list. 2nd ed. Golden Gate Audubon Soc., Berkeley. Reprinted with suppl. 108pp.
Michael, C W. 1927. Black swifts nesting in Yosemite National Park. Condor 29: 89-97.
Remsen, J. V., Jr. 1978. Bird species of special concern in California. Calif. Dep. Fish and Game, Sacramento. Wildl. Manage. Admin. Rep. No. 78-1. 54pp.
Stephenson, J. R. and G. M. Calcarone. 1999. Southern California mountains and foothills assessment: habitat and species conservation issues. General Technical Report GTR-PSW-172. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. 402 pp.
Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. A. Knopf, New York. 1100pp.
Udvardy, M. D. F. 1954. Summer movements of black swifts in relation to weather conditions. Condor 56:261-267.
Zeiner, D.C., W. F. Laudenslayer, K. E. Mayer and M. White eds. 1990. California's Wildlife: Volume II - Birds. California Department of Fish and Game. Sacramento, California. 732pp.
burrowing owl (Athene cunicularia hypugaea)
State: Species of Special Concern
Federal: Federal Special Concern species; Partners in Flight Priority Bird Species; Fish and Wildlife Service Species of Management Concern
The burrowing owl is narrowly distributed at relatively few locations within the Plan Area in suitable habitat. Although the preferred habitat, grassland and some forms of agriculture land, is well distributed, the recent locations of the burrowing owl are clumped in only a few locations. Because this species requires specific soil and micro-habitat conditions, occurs in few locations within a broad habitat category, requires a relatively large home range to support its life history requirements, occurs in relatively low numbers, and is semi-colonial, the burrowing owl will require site-specific considerations and management conditions.
This is a species on the Additional Survey Needs and Procedures (Section 6.3.2) list and surveys for burrowing owl will be conducted as part of the project review process for public and private projects within the burrowing owl survey area where suitable habitat is present (see Burrowing Owl Survey Area Map, Figure 6-4 of the MSHCP, Volume I). Burrowing owls located as a result of survey efforts shall be conserved in accordance with procedures described within Section 6.3.2, MSHCP, Volume 1.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 27,470 acres of suitable primary habitat for the burrowing owl including grasslands.
Include within the MSHCP Conservation Area at least 5 Core Areas and interconnecting linkages. Core areas may include the following: (1) Lake Skinner/Diamond Valley Lake area (Existing Core C plus Proposed Extension of Existing Cores 5, 6, 7; 29,060 acres); (2) playa west of Hemet (Proposed Noncontiguous Habitat Block 7; 1,250 acres); (3) San Jacinto Wildlife Area/Mystic Lake area including Lake Perris area (Existing Core H; 17,470 acres); (4) Lake Mathews (Existing Core C plus Proposed Extension of Existing Cores 2; 23,710 acres); and (5) along the Santa Ana River (9,670 acres). The Core Areas should support a combined total breeding population of approximately 120 burrowing owls with no fewer than five pairs in any one Core area.
Include within the MSHCP Conservation Area at least 22,120 acres of suitable secondary habitat for the burrowing owl including playas and vernal pools, and agriculture outside of the Core Areas identified above. Areas where additional suitable habitat could be conserved include west of the Jurupa Mountains, near Temescal Wash (i.e., vicinity of Alberhill), near Temecula Creek, within the Lakeview Mountains, Banning, the Badlands, Gavilan Hills, and Quail Valley.
Include within the MSHCP Conservation Area the known nesting locations of the burrowing owl at Lake Perris, Mystic Lake/San Jacinto Wildlife area, Lake Skinner area, the area around Diamond Valley Lake, playa west of Hemet, Lakeview Mountains, Lake Mathews/Estelle Mountain Reserve and Sycamore Canyon Regional Park.
Surveys for burrowing owl will be conducted as part of the project review process for public and private projects within the burrowing owl survey area where suitable habitat is present (see Burrowing Owl Survey Area Map, Figure 6-4 of the MSHCP, Volume I). The locations of this species determined as a result of survey efforts shall be conserved in accordance with procedures described within Section 6.3.2, MSHCP, Volume I and the guidance provided below:
Burrowing owl surveys shall be conducted utilizing accepted protocols as follows. If burrowing owls are detected on the project site then the action(s) taken will be as follows:
If the site is within the Criteria Area, then at least 90 percent of the area with long-term conservation value will be included in the MSHCP Conservation Area. Otherwise:
The survey and conservation requirements stated in this objective will be eliminated when it is demonstrated that Objectives 1 – 4 have been met.
Pre-construction presence/absence surveys for burrowing owl within the survey area where suitable habitat is present will be conducted for all Covered Activities through the life of the permit. Surveys will be conducted within 30 days prior to disturbance. Take of active nests will be avoided. Passive relocation (use of one way doors and collapse of burrows) will occur when owls are present outside the nesting season.
Translocation sites for the burrowing owl will be created in the MSHCP Conservation Area for the establishment of new colonies. Translocation sites will be identified, taking into consideration unoccupied habitat areas, presence of burrowing mammals to provide suitable burrow sites, existing colonies and effects to other Covered Species. Reserve Managers will consult with the Wildlife Agencies regarding site selection prior to translocation site development.
The burrowing owl uses predominantly open land, including grassland, agriculture (e.g., dry-land farming and grazing areas), playa, and sparse coastal sage scrub and desert scrub habitats (Garrett and Dunn 1988). Some breeding burrowing owls are year-round residents and additional individuals from the north may winter throughout the MSHCP Area Plan. For the purpose of the conservation analysis, the primary habitat of the species is considered to include only grassland. The burrowing owl is also known to use some forms of agricultural lands, playa and vernal pool (especially in its grassy condition) and sparsely vegetated scrub habitats. However, these habitat types are considered to be secondary in importance. Due to the overall low occurrence of sparse scrub habitat within the larger habitat category of coastal sage scrub, this habitat type is not included in the analysis. Based on these habitats, the Area Plan supports a total of approximately 109,960 acres of potential primary habitat and approximately 123,520 acres of secondary habitat for the burrowing owl. Table 1 shows the conservation and loss of potential habitat for the burrowing owl. Overall, approximately 27,470 acres (25 percent) of potential primary habitat and 22,120 acres (18 percent) of secondary habitat in the Area Plan will be conserved.
As described below under Data Characterization, 38 of the 82 recent point localities have a high location precision. Of these 38 point localities, 16 will be inside the MSHCP Conservation Area or Public/Quasi-Public Lands. A total of 22 point localities will be outside of the MSHCP Conservation Area.
Five of the six Core Areas will be conserved within Criteria Area and Public/Quasi-Public designations including Lake Skinner/Diamond Valley Lake area (Existing Core C plus Proposed Extension of Existing Cores 5, 6, 7; 29,060 acres); playa west of Hemet (Proposed Noncontiguous Habitat Block 7; 1,250 acres); San Jacinto Wildlife Area/Mystic Lake area including Lake Perris area (Existing Core H; 17,470 acres); Lake Mathews (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres); and along the Santa Ana River (9,670 acres). The total acreage of Core Areas within Criteria Area and Public/Quasi-Public Lands is 81,160 acres. The Core Areas must support a breeding population of approximately 120 burrowing owls combined total (but no fewer than 5 pairs in any one Core Area). Other burrowing owl locations within areas that do not consist of a Core Area also will be conserved within the MSHCP Conservation Area including: the vicinity of Alberhill, between San Jacinto River and Lakeview Mountains, along Santa Gertrudis Creek and Tucalota Creek, and Steele Peak, Sycamore Canyon Regional Park, and the Badlands.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
BURROWING OWL
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Riverside Lowland Bioregion | |||||||
| Primary Habitat | |||||||
| Grassland | 109,960 | 12,820 | 14,650 | 27,470 | 5,650 | 76,840 | 82,490 |
| Subtotal Primary Habitat | 109,960 | 12,820 (12%) |
14,650 (13%) |
27,470 (25%) |
5,650 (5%) |
76,840 (70%) |
82,490 (75%) |
| Secondary Habitat | |||||||
| Agriculture (field crops) | 115,650 | 5,590 | 9,820 | 15,410 | 490 | 99,750 | 100,240 |
| Playas and Vernal Pools | 7,870 | 3,820 | 2,890 | 6,710 | 0 | 1,160 | 1,160 |
| Subtotal Secondary Habitat | 123,520 | 9,410 (8%) | 12,710 (10%) | 22,120 (18%) | 490 (<1%) | 100,910 (82%) | 101,400 (82%) |
| TOTAL | 233,480 | 22,230 (9%) |
27,360 (12%) |
49,590 (21%) |
6,140 (3%) |
177,750 (76%) |
183,890 (79%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Available data is not adequate to fully determine the distribution of burrowing owls in the MSHCP Conservation Area or how much conservation the MSHCP Conservation Area will provide. In addition, individual burrowing owl pairs in the Plan Area may be important to the conservation of the species in the Plan Area and Take of individuals will be minimized. Therefore, objectives have been incorporated into the conservation strategy for this species, and are summarized below, to provide assurance of protection and management of a suitable number of known and future localities to conserve this species. Minimization efforts are focused at actively and/or passively relocating burrowing owls from development areas to appropriate MSHCP Conservation Area lands.
Surveys for western burrowing owl will be conducted as part of the project review process for public and private projects within the Criteria Area where suitable habitat is present (see Burrowing Owl Survey Area Map, Figure 6-4 of the MSHCP, Volume I). The locations of this species determined as a result of survey efforts shall be conserved in accordance with procedures described within Section 6.3.2, MSHCP, Volume 1 and the guidance proved below:
Burrowing owl surveys shall be conducted utilizing the protocols identified in the CDFG Staff Report on Burrowing Owl Mitigation. If burrowing owls are detected on the project site then the action(s) taken will be as follows: If the site is within the Criteria Area, then at least 90 percent of the area with long-term conservation value will be included in the MSHCP Conservation Area. Otherwise:
The survey and conservation requirements stated in this objective will be eliminated when it is demonstrated that Objectives 1 – 4 have been met.
Pre-construction presence/absence surveys for burrowing owl will be conducted for all Covered Activities through the life of the permit. Surveys will be conducted within 30 days prior to disturbance. Take of active nests will be avoided. Passive relocation (use of one way doors and collapse of burrows) will occur when owls are present outside the nesting season.
Translocation sites for the burrowing owl will be created in the MSHCP Conservation Area for the establishment of new colonies. Translocation sites will be identified, taking into consideration unoccupied habitat areas, presence of burrowing mammals to provide suitable burrow sites, existing colonies and effects to other Covered Species. The Wildlife Agencies will concur with the site selection prior to translocation site development.
Several large blocks of habitat supporting the current known and potential foraging and nesting locations of the burrowing owl will be conserved as MSHCP Conservation including the Lake Skinner/ Diamond Valley Lake area, playa west of Hemet, Lake Perris/Mystic Lake area, Lake Mathews, and Santa Ana River area, and more isolated locations are preserved in the large blocks of habitat at Alberhill, Sycamore Canyon Regional Park, Badlands, Motte-Rimrock Reserve, Steele Peak, Vail Lake, and Wilson Creek with smaller areas preserved in Antelope Valley. Additional areas that provide potential habitat include Lake Elsinore grasslands, Sedco Hills, Box Springs Mountain, Lakeview Mountains, Sage, and foothills of the national forest lands. As identified below, the species occurs within the MSHCP Area Plan as a breeding and wintering resident and as such, the MSHCP Conservation Area will provide adequate habitat for foraging and breeding. These MSHCP Conservation Area areas are linked as well, however the burrowing owl, due to its ability to move long distances and semi-migratory status within the Area Plan, may rely less on the linkages than other species.
In summary, conservation for this species will be achieved by inclusion of at least 27,470 acres of suitable primary Conserved Habitat and 22,120 acres of suitable secondary Conserved Habitat and 5 of 6 Core Areas within large blocks of habitat in the MSHCP Conservation Area. In addition, 16 recent and high precision locations will be inside the Criteria Area or Public/Quasi-Public Lands. Conservation also will be provided for the habitat linkages between Core Areas and areas important for dispersal as described above. The current population size of the burrowing owl is unknown, however the foraging and nesting habitat requirements are well defined. Surveys will be conducted and locations of owls will be conserved in accordance with procedures described in Section 6.3.2, MSHCP, Volume 1. The Conservation Strategy of this species includes pre-construction surveys of potential habitat areas and conservation as appropriate until sufficient conservation is attained because it occurs in grassland habitats that are not relatively abundant within the MSHCP Conservation Area and the distribution of the species within the Plan Area is not well known. These surveys will provide the information to determine whether the area is currently being used by the species and will supplement the known locations. Translocation of burrowing owls may be used if necessary to establish colonies in currently unoccupied areas.
The Incidental Take of the burrowing owl is difficult to quantify due to our limited knowledge of its distribution within the Plan Area and the fact that losses may be masked by fluctuations in abundance and distribution during the life of the permit. However, the maximum level of Take of burrowing owl can be anticipated by the loss of the number of acres of habitat that will become unsuitable for this species. About 82,490 acres (75 percent) of the primary potential habitat for the burrowing owl will be outside of the Criteria Area or Public/Quasi-Public lands and individuals within these areas are subject to Incidental Take consistent with the Plan. About 101,400 acres (82 percent) of the secondary potential habitat for the burrowing owl will be outside of the Criteria Area or Public/Quasi-Public Lands and individuals within these areas are subject to Incidental Take consistent with the Plan. A total of 22 point localities recorded within the UCR database will be outside of the MSHCP Conservation Area. Core Areas not conserved include Valle Vista. Smaller numbers of clustered locations of burrowing owls that will be outside the Criteria Area and Public/Quasi-Public Lands, include those locations at the area west of the Jurupa Mountains, San Jacinto, Rancho California area (Long Canyon and De Portola Road), and March ARB. Historically, there were a number of locations concentrated within the Moreno Valley area, however due to the age of the location and the development within the area, the number currently within this area is unknown and receives no conservation within the MSHCP Conservation Area. Individual locations that are outside the MSHCP Conservation Area include locations at Beaumont, Banning, and Murrieta.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The UCR location database includes approximately 109 records for the western burrowing owl within the Area Plan dated from 1887 to 1999. Approximately 82 records are relatively recent (within the past 10 years) and of these recent records, 38 are high precision records that can be accurately placed within the area. The habitat types associated with these recent and high precision data records include residential, riparian (probably represents grassland at the edge of a drainage), grassland, coastal sage scrub, alkali playa, and crop lands. The residential habitat records may reflect records that are either no longer extant or where the location is a small pocket of suitable habitat within or adjacent to a developed area. The locations are predominantly recorded for crop land habitats within the Area Plan. Breeding locations have not been identified within the UCR database, however, due to the sedentary nature of the species, locations are likely near a breeding location.
The literature available on the burrowing owl is relatively large. It is focused on the natural history of the species, and also includes physiological studies and management studies including a trapping and relocation protocol. Several general ornithological reference treatments have been prepared for the species and it has been treated within the general raptor literature. A summary of available information as well as proceedings from a symposium (Lincer and Steenhof 1997) provides substantial information for the species, only a small part of which is presented within this species account. Little information is available with respect to the Area Plan other than general distribution and occurrence information.
The burrowing owl occurs in shortgrass prairies, grasslands, lowland scrub, agricultural lands (particularly rangelands), prairies, coastal dunes, desert floors, and some artificial, open areas as a year-long resident (Haug, et al. 1993). They may also use golf courses, cemeteries, road allowances within cities, airports, vacant lots in residential areas and university campuses, fairgrounds, abandoned buildings, and irrigation ditches (Haug, et al. 1993; Hayworth 1990 pers. obs.). They may also occur in forb and open shrub stages of pinyon-juniper and ponderosa pine habitats (Zeiner, et al. 1990). They require large open expanses of sparsely vegetated areas on gently rolling or level terrain with an abundance of active small mammal burrows. As a critical habitat feature need, they require the use of rodent or other burrows for roosting and nesting cover. They may also dig their own burrow in soft, friable soil (as found in Florida) and may also use pipes, culverts, and nest boxes where burrows are scarce (Robertson 1929). The mammal burrows are modified and enlarged. One burrow is typically selected for use as the nest, however, satellite burrows are usually found within the immediate vicinity of the nest burrow within the defended territory of the owl.
The burrowing owl breeds from southern interior British Columbia (nearly extirpated), southern Alberta, southern Saskatchewan (extirpated from a portion of the province), and southern Manitoba (extirpated from a portion of the province), south through eastern Washington, central Oregon, and California to Baja California, east to western Minnesota, northwestern Iowa, eastern Nebraska, central Kansas, Oklahoma, eastern Texas, and Louisiana, and south to central Mexico. The winter range is much the same as the breeding range, except that most burrowing owls apparently vacate the northern areas of the Great Plains and Great Basin (Haug, et al. 1993). The burrowing owl winters south regularly to El Salvador (e.g., AOU 1998).
Historical changes in the distribution of the burrowing owl include the recent extirpation from British Columbia for which the last confirmed sighting was in 1979. Elsewhere is Canada and the north-central U.S., the range has contracted slightly southward, westward, and eastward (Haug et al. 1993). In Florida, the range has expanded northward, nearly to Georgia since the 1950s (Courser 1979).
Zeiner et al. (1990) describe the distribution, abundance, and seasonality of the burrowing owl within California as follows. It is a year-long resident formerly common in appropriate habitats throughout the state, excluding the humid northwest coastal forests and high mountains. It is present on the larger offshore islands and is found as high as 1,600 m (5,300 ft) in Lassen County. In California, burrowing owls are restricted to the central valley extending from Redding south to the Grapevine, east through the Mojave Desert and west to San Jose, the San Francisco Bay area, the outer coastal foothills area which extend from Monterey south to San Diego and the Sonoran desert (Grinnell and Miller 1944). It is a resident in the open areas of the lowlands over much of the southern California region (Garrett and Dunn 1981). It is greatly reduced in number within the lowlands of Riverside County and appears to be resident within the region although there is some movement of more northerly birds into the southern and coastal parts of the region (Garrett and Dunn 1981).
Within Western Riverside County, the burrowing owl occurs within the central portion within the open lowlands (Garrett and Dunn 1981). It has a sparsely scattered distribution throughout the Area Plan outside of the montane areas. Breeding and burrow locations have not been identified within the UCR database, although most observations that have been recorded are probably located near a burrow due to the relatively sedentary habits of the species.
The species has been detected east of the Jurupa Mountains, along the Santa Ana River, at Lake Mathews, at Good Hope, Alberhill, Murrieta, March Air Reserve Base, the Lake Perris/Mystic Lake area, the Badlands, within the vicinity of Beaumont and Banning, San Jacinto, Valle Vista, between San Jacinto River and Lakeview Mountains, west of Hemet, the area around Diamond Valley Lake, east and south of Lake Skinner area, along Santa Gertrudis Creek and Tucalota Creek, in Long Canyon, and along De Portola Road as documented in the UCR database and from other sources (USFWS 1996 unpublished data; California Science and Engineering Associates 1996).
Based on the information above, clusters of locations, and information from the USFWS (1996 unpublished data), the Core Areas may include Santa Ana River, Lake Mathews area, Lake Perris/Mystic Lake, playa west of Hemet, Lake Skinner/Diamond Valley Lake area, and Valle Vista. Smaller numbers of clustered locations include the area west of the Jurupa Mountains, San Jacinto, Rancho California area (Long Canyon and De Portola Road), and March ARB. Historically, there were a number of locations concentrated within the Moreno Valley area, however due to the age of the location and the development within the area, the number currently within this area is unknown.
Genetics: The burrowing owl has been variously placed in the monotypic genus Speotyto or in Athene, where it has three congeners (Haug, et al. 1993). Comparison with other karyotypes in the literature suggests that the burrowing owl should be in a separate genus, Speotyto, as has been done for a number of years although it is frequently still referred to as Athene (Schmutz and Moker 1991).
Diet and Foraging: The burrowing owl is a crepuscular hunter with a prey base including invertebrates and small vertebrates (Thomsen 1971). They may hunt by using short flights, running along the ground, hovering or by using an elevated perch from where prey is spotted. They typically forage in short-grass, mowed, or overgrazed pasture, golf courses and airports (Thomsen 1971).
They are a relatively opportunistic forager (Haug, et al. 1993). Their diet is composed of a variety of foods included Peromyscus, Microtus and beetles. Beetles occur within their diet with more frequency, however, based on biomass, Peromyscus is dominant with Microtus appearing second in overall biomass (Marti 1974). Although they eat mostly insects and small mammals, they also may take reptiles, birds, and carrion. During the breeding season, there are significant declines in the percentage of vertebrate prey in the diet and increases in the invertebrate prey (Haug, et al. 1993).
Daily Activity: The burrowing owl is primarily a diurnal species with crepuscular hunting habits (Thomsen 1971). They may move the location of their perch in order to thermoregulate by perching in open sunlight in early morning and then moving to shade or to the burrow, when temperatures are hot (Coulombe 1971).
Reproduction: The burrowing owl usually nests in an old burrow of a ground squirrel, or other small mammal, and may also use the burrow of badgers and marmots. It may dig its own burrow in soft soil. The nest chamber is lined with excrement, pellets, debris, grass, feathers; sometimes it is unlined. Pipes, culverts, and nest boxes are used where burrows are scarce (Robertson 1929). The male gives a courtship display and notes in front of the burrow. Breeding occurs from March through August, with a peak in April and May. The clutch size is 6-11 eggs, with an average of 7-9 eggs; this clutch size may increase to the north (Bent 1938). The young emerge from the burrow at about two weeks, and they fly by about four weeks (Zarn 1974). Martin (1973) reported 95 percent of the young fledged, and a mean reproductive success of 4.9 young per pair. The species is semi-colonial; it is probably the most gregarious owl in North America.
Nest success was 50 to 57 percent at a site in Oregon with desertion being the major cause of nest failures and typically was related to the proximity to other nesting pairs. Burrow sites with good horizontal visibility and little grass coverage were preferred. Elevated perches were used in habitat with average vegetation height greater than 5 centimeters and not in habitats with vegetation less than 5 centimeters. The elevated perches presumably improved the burrowing owl's ability to detect both predators and prey by increasing their horizontal visibility (Green and Anthony 1989). MacCracken et al. (1985) found that nest burrows were in soils with a greater sand content than non-nest burrows, suggesting that selection for soil type may occur. All nest burrows found to be reused in a study in Oregon were in silty loam (Green 1983).
Survival: The minimum annual survival rates in Florida average 68 percent for adult males, 59 percent for adult females and 19 percent for one year old owls (Millsap and Bear 1992). In southern California, the apparent survival rates are 30 percent for juveniles and 81 percent for adults (Thomsen 1971). One banded bird survived to 8 years 8 months (Kennard 1975). Collisions with autos may be a significant cause of mortality (Remsen 1978).
Dispersal: A total of 92 percent of 555 owls that were banded at a nesting area were never re-encountered after the year in which they were banded. The 8 percent that returned to the natal area after being banded, returned one or more years after banding and stayed in the natal area for 2 to 4 breeding seasons (Lutz and Plumpton 1999). Returns of one year old owls were located 2.4 to 26.4 kilometers from the natal nest (Haug et al. 1993).
Socio-Spatial Behavior: The home range may vary from 0.1 to 4 acres (mean is 2 acres) with an average distance between burrows of 436 feet (Thomsen 1971, Martin 1973). Territory size is directly proportional to the available habitat and burrow availability (Haug et al. 1993).
Community Relationships: Predators include prairie falcons, red-tailed hawks, Swainson's hawks, ferruginous hawks, northern harriers, golden eagles, foxes, coyotes, and domestic dogs and cats (Martin 1973). Fleas, lice, and feather mites are common ectoparasites (Zeiner et al. 1990).
They require an abundance of active small mammal burrows. The availability of numerous small mammal burrows is a major factor in determining whether an area with apparently suitable habitat will support burrowing owls (Coulombe 1971). Burrowing owls rarely use areas unoccupied by colonies of burrowing mammals (Zarn 1974).
Potential competition with other owl species is avoided by the burrowing owls habit of hunting at a crepuscular time period and using other prey species including insects in their diets (Marti 1974).
The threats to the burrowing owl include conversion of grassland to agriculture, other habitat destruction, predators, collisions with vehicles, and pesticides/poisoning of ground squirrels (Grinnell and Miller 1944, Zarn 1974, Remsen 1978). A ranking by the resource agencies of the most important threats to the species included loss of habitat, reduced burrow availability due to rodent control, and pesticides (James and Espie 1997).
The burrowing owl was formerly common in appropriate habitats throughout the state, excluding the humid northwest coastal forests and high mountains. Population numbers have markedly reduced in recent decades (James and Ethier 1989; Zeiner et al. 1990). The primary threats to the species include the loss of natural habitat due to urban development and agriculture and the expressed effects of insecticides and rodenticides within occupied habitat. The use of insecticides may reduce the availability of their primary prey. Pesticides may have secondary adverse effects through contamination. The pesticide Carbofuran has been demonstrated to have negative impacts; Sevin is likely a safer pesticide (Hjertaas et al. 1995; Blus 1996). The loss of burrowing mammal colonies (due to rodenticides or other means) and the crushing of burrows by heavy equipment and ground maintenance machinery remain problematic. This species is usually associated with flat or shallow slopes on loamy soils; these areas are also attractive to agriculture, as well as residential and industrial development. Shooting losses may be significant (Remsen 1978).
The burrowing owl received official status as Endangered in Canada as of 1986. Burrowing owls have gone from locally common to virtually extirpated in Minnesota in 50 years (Johnsgard 1988). The number of burrowing owl breeding pairs in central, western, and southern California have drastically declined in the last 50 years; during the 1980's the decline was probably greater than 70 percent (DeSante and Ruhlen 1995). The species appears to be seriously threatened with extirpation from central, western, and southern California because of the extent and intensity of development (DeSante and Ruhlen 1995).
Physiological ecology studies have shown that the burrowing owl is able to dissipate 135 percent of their heat production by use of pulmocutaneous evaporation facilitated by gular flutter. This allows the species to use areas that may have air temperatures greater than their body temperature. They also were found to have different emissivities of their feathers depending on the season of year. During the winter, the emissivity of the plumage is greater thus allowing them to augment their metabolic heat production with solar radiative heat gain (Coulombe 1970).
The importance of retaining colonies must be stressed, as this species appears to have evolved as a colonial species in association with burrowing mammal communities (Dyer 1987). Minimum viable colony size is unknown. While these owls appear to adapt fairly well to human presence in some cases, i.e., airport runways and other human modified open spaces, the continued presence of active mammal-created burrows is essential. In Oklahoma, the removal of prairie dogs allowed deterioration of burrows, making them unsuitable for nest burrows after one year (Butts 1973). Rodent eradication programs may reduce the consistent availability of high and moderate function habitat. The remaining habitat is often roadside drainage ditches, increasing potential for significant losses to vehicle collisions (Remsen 1978). The available soil type appears to be a factor in nest burrow selection (see Reproduction section above).
The burrowing owl was shown to choose moderately to heavily grazed grasslands for nesting and roosting and avoided cultivated fields. Where grassland patches were isolated in cultivation areas, the owls dispersed late, for shorter distances and less often. Mortality rate has been shown to be high in these systems. These changes from pasture to cultivation appear to be resulting in a decline of the species (Clayton and Schmutz 1999). It is also important to determine what type and where within the region owls are selecting burrows before the area is disturbed and before it is decided to provision them with artificial burrows. Burrowing owls produced fewer young when occupying a new burrow, and when using burrows in disturbed areas. They produced more young when using artificial burrows but produced fewer fledglings than natural burrows, thus the actual productivity decreased for the artificial burrows (Botelho and Arrowood 1998).
The role of food in limiting the number of offspring fledged from nests has been experimentally investigated in the burrowing owl (Wellicome 1997). Food-supplemented owls laid slightly larger clutches and produced eggs of higher volume but did not show higher hatching success or produce more hatchlings than did the unsupplemented birds. Therefore, although food intake may restrict the number of eggs that burrowing owls lay, the total number of young produced at a nest is constrained by food only during the nestling period. Food intake is thus more limiting during brood rearing than during egg laying (Wellicome 1997).
Urban sites can act as unintentional preserves and support owl populations if habitat features necessary for owls are provided. This is supported by the documented population at Moffett Field in Santa Clara County California. The population has established itself and is using nest burrows under cement or other hard surfaces. The adult density, number of young fledged or pairs with emergent young is not different at Moffett Field compared to other intentional preserve areas (Trulio 1997).
Human activities have had a beneficial effect in Florida where mowing, grazing of cattle and wetland drainage have increased the species' range. Residential and industrial areas currently support the largest concentrations of the species in Florida (Haug et al. 1993).
Because of the intense pressure for urban development within suitable burrowing owl nesting and foraging habitat in California, conflicts between owls and development projects often occur. Owl survival can be adversely affected by disturbance and foraging habitat loss even when impacts to individual birds and nest/burrows are avoided (CDFG 1995). The Staff Report on Burrowing Owl Mitigation (CDFG 1995) outlined the protocol for determining impact assessment. The project site and a 150-meter buffer should be surveyed according to the survey protocol and impacts to the owl should be considered to occur if there is disturbance within 50 meters of a burrow, or there is destruction of natural or artificial burrows, or there is destruction of foraging habitat within 100 meters of a burrow. Mitigation measures should include the provision of 6.5 acres of foraging habitat per pair, provision of two burrows for each burrow impacted, relocation of owls (Trulio 1995), and avoidance of the nesting season.
Given the extraordinary, precipitous decline of this species in cismontane southern California (Grinnell and Miller 1944; Sexton and Hunt 1979; Garrett and Dunn 1981; Hamilton and Willick 1996), it cannot be assumed that preferred habitat patches (e.g., dry, level grasslands and open areas with suitable nesting substrates) within the Area Plan continue to accommodate the species in numbers, similar to those in past years (Grinnell and Miller 1944). For instance, this species, fairly common in the Prado Basin and environs as recently as 1986, is now rare at that locale (Hays 1999 pers. obs.).
The following have been suggested as management strategies (Green 1983): protection of burrowing mammal populations; wood or plastic nest boxes and tunnels; artificial perches which provide hunting and predator observation sites; vegetation management through fire or grazing; and relocation of owls. Other management strategies include: reduce mortality on the breeding grounds, increase productivity, protect and manage the nesting habitat, monitor the populations, manage migration and wintering areas, conduct release programs, and develop public support (Hjertaas 1997).
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Bent, A. C. 1938. Life histories of North American birds of prey. Part 2. U.S. Natl. Mus. Bull. 170. 482pp.
Botelho, E. S. And P. C. Arrowood. 1998. The effect of burrow site use on the reproductive success of a partially migratory population of western burrowing owls (Speotyto cunicularia hypugaea). J. Raptor Research 32: 233-240.
Blus, L. J. 1996. Effects of pesticides on owls in North America. J. Raptor Research 30: 198-206.
Butts, K. O. 1973. Life history and habitat requirements of burrowing owls in western Oklahoma. Unpublished MS thesis, Oklahoma State University, Stillwater. 188 pp.
California Science and Engineering Associates. 1996. Final threatened and endangered species survey, March Air Reserve Base, Riverside County, California.
California Department of Fish and Game (CDFG). 1995. Staff Report on Burrowing owl mitigation. State of California.
Clayton, K. M and J. K. Schmutz. 1999. Is the decline of burrowing owls, Speotyto cunicularia in prairie Canada linked to changes in the Great Plains ecosystems? Bird Conservation International 9: 163-185.
Coulombe, H. N. 1970. Physiological and physical aspects of temperature regulation in the burrowing owl Speotyto cunicularia. Comp. Biochem. Physiol. 35: 307-337.
Coulombe, H.N. 1971. Behavior and population ecology of the burrowing owl, Speotyto cunicularia, in the Imperial Valley of California. Condor 73: 162-176.
Courser, W. D. 1979. Continued breeding range expansion of the burrowing owl in Florida. Amer. Birds 33: 143-144.
DeSante, D.F. and E.D. Ruhlen. 1995. (draft) A census of burrowing owls in California, 1991-1993.
Dyer, O. 1987. Burrowing owl workshop - Western Raptor Management Symposium: a summary of discussions.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Green, G. A. 1983. Ecology of breeding burrowing owls in the Columbia basin, Oregon. M.Sc. Thesis. Oregon State University, Corvallis. 51 pp.
Green, G. A., and R. G. Anthony. 1989. Nesting success and habitat relationships of burrowing owls in the Columbia Basin, Oregon. Condor 91: 347.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Copper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April 1986. 617 pp.
Hamilton, R. and D. R. Willick. 1996. The Birds of Orange County, California: Status and Distribution. Sea and Sage Press, Irvine, California. 150 pp. with appendices.
Haug, E. A., B. A. Millsap, and M. S. Martell. 1993. Burrowing Owl (Speotyto cunicularia). In The Birds of North America, No. 130 (A. Poole and F. Gill, Eds.) . Philadelphia: The Academy of Natural Sciences; Washington, D.C.: The American Ornithologists' Union.
Hays, L. R. 1999. USFWS, pers. obs.
Hayworth, A. H. 1990 pers. obs.
Hjertaas, D., S. Brechtel, K. De Smet, O. Dyer, E. Haug, G. Holroyd, P. James, and J. Schmutz. 1995. National Recovery Plan for the Burrowing Owl. Report No. 13. Ottawa: Recovery of the Nationally Endangered Wildlife Committee. 33 pp.
Hjertaas, D. G. 1997. Recovery plan for the burrowing owl in Canada. Journal of Raptor Research Report 9:107-111.
James, P.C., and T. J. Ethier. 1989. Trends in the winter distribution and abundance of burrowing owls in North America. American Birds 43:1224-1225.
James, P.C. and R.H.M. Espie. 1997. Current status of the burrowing owl in North America: an agency survey. Journal of Captor Research Report 9:3-5.
Johnsgard, P. A. 1988. North American owls, biolgoy and natural history. Smithsonian Inst. Press, Washington, D. C.
Kennard, J. H. 1975. Longevity records of North American birds. Bird-banding 46: 55-73.
Lincer, J. L., and K. Steenhof . [eds]. 1997. The burrowing owl, its biology and management: including the Proceedings of the First International Symposium. Raptor Research Report Number 9.
Lutz, R. S., and D. L. Plumpton. 1999. Philopatry and nest site reuse by burrowing owls: implications for productivity. J. Raptor Research 33: 149-153.
MacCracken, J.G., D.W. Uresk, and R.M. Hansen. 1985. Vegetation and soils of burrowing owl nest sites in Conata Basin, South Dakota. Condor 87:152-154.
Marti, C. D. 1974. Feeding ecology of four sympatric owls. Condor 76: 45-61.
Martin, D. C. 1973. Selected aspects of burrowing owl ecology and behavior. Condor 75: 446-456.
Millsap, B. A. and C. Bear. 1992. Double-brooding by Florida Burrowing Owls. Wilson Bull. 102: 313-317.
Pacific Southwest Biological Services. 1991. Western Riverside County Multi-species Habitat Conservation Plan.
Remsen, J. V., Jr. 1978. Bird species of special concern in California. Calif. Dep. Fish and Game, Sacramento. Wildl. Manage. Admin. Rep. No. 78-1. 54pp.
Robertson, J. M. 1929. Some observations on the feeding habits of the burrowing owl. Condor 31: 38-39.
Sexton, C.W. and G.L. Hunt. 1979. An annotated checklist of the birds of Orange County, California. University of California Irvine Museum of Systematic Biology Research Series No. 5.
Schmutz, S. M., and J. S. Moker. 1991. A cytogenetic comparison of some North American owl species. Genome 34: 714-717.
Thomsen, L. 1971. Behavior and ecology of burrowing owls on the Oakland Municipal airport. Condor 73: 177-192.
Trulio, L. A. 1995. Passive relocation: a method to preserve burrowing owls on disturbed sites. J. Field Ornithology 66: 99-106.
Trulio, L. 1997. Burrowing owl demography and habitat use at two urban sites in Santa Clara County, California. Journal of Raptor Research Report 9:84-89.
USFWS. 1996. unpublished data.
Wellicome, T. I. 1997. Reproductive performance of burrowing owls (Speotyto cunicularia): effects of supplemental food. Journal of Raptor Research Report 9: 68-73.
Zarn, M. 1974. Burrowing Owl, Report No. 11. Habitat management series for unique or endangered species. Bureau of Land Management, Denver. 25 pp.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
cactus wren (Campylorhynchus brunneicapillus)
State: Species of Special Concern
Federal: Cleveland National Forest Sensitive
The cactus wren is narrowly distributed at relatively few locations in suitable habitat within the Plan Area. Although the preferred habitat, coastal sage scrub, desert scrubs, and Riversidean alluvial fan sage scrub is well distributed, the locations of the cactus wren are clumped in few locations due to its specific habitat requirements. It requires patches of cactus-dominated sage scrub habitat in the Riverside Lowland and San Jacinto Foothill Bioregions of the Plan Area. Because this species has specific habitat requirements (cactus patches), occurs in few locations within a broader habitat category, and occurs in relatively low numbers within the Plan Area, the cactus wren will require site-specific considerations, a landscape level of management, and species-specific conservation measures as a Group 3 species.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 77,070 acres of suitable habitat for the cactus wren including desert scrub, Riversidean alluvial fan sage scrub, and coastal sage scrub within Riverside Lowland and San Jacinto Foothill Bioregions.
Include within the MSHCP Conservation Area at least 11 Core Areas and interconnecting linkages including Chino Hills (Proposed Extension of Existing Core 1; 270 acres), Badlands (Proposed Core 3; 24,920 acres), Box Springs Mountains (Existing Noncontiguous Habitat Block A plus Proposed Constrained Linkages 7 and 8; 4,000 acres), Lake Mathews-Estelle Mountain area (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres), Alberhill (Subunit 2 of Elsinore Area Plan; 3,460 acres), Motte-Rimrock area MSHCP Conservation Area (Proposed Noncontiguous Habitat Block 4; 1,150 acres), Lake Perris/Bernasconi Hills (Existing Core H; 17,470 acres), Lake Skinner (Existing Core C plus Proposed Extension of Existing Cores 5, 6, 7; 29,060 acres), Vail Lake (Subunit 3 of Southwest Area Plan; 12,320 acres), Wilson Valley (Subunit 2 of REMAP Area Plan; 33,540 acres), and Aguanga (Subunit 4 of REMAP Area Plan; 2,660 acres).
Include within the MSHCP Conservation Area micro-habitat (i.e., cactus patches) in potential nesting habitat.
The cactus wren is restricted to cactus-dominated stands of coastal sage scrub below 457 meters in elevation on mesas and lower slopes of the coast ranges (Proudfoot et al. 2000). For the purpose of the conservation analysis and based on the matching of the distribution of the species with the appropriate Bioregions, potential habitat for the cactus wren includes desert scrubs, Riversidean alluvial fan sage scrub, and coastal sage scrub within the Riverside Lowland and San Jacinto Foothills Bioregions. Based on these habitats, the Area Plan supports approximately 140,770 acres of potential habitat for the cactus wren. Table 1 shows the conservation and loss of potential habitat for the cactus wren. Overall, approximately 77,070 acres (55 percent) of potential habitat in the Area Plan will be conserved in Criteria Area or existing Public/Quasi-Public Lands. Although the habitats used in this analysis includes more acreage than is considered suitable habitat, the cactus-dominated sage scrub is imbedded within the broader categories of habitat. Mapping of cactus-dominated sage scrub is not available for the Area Plan.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
CACTUS WREN
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Riverside Lowlands and San Jacinto Foothills Bioregions | |||||||
| Desert Scrubs | 2,230 | 2,160 | 0 | 2,160 | 40 | 30 | 70 |
| Riversidean Alluvial Fan Sage Scrub | 5,430 | 2,710 | 1,310 | 4,020 | 160 | 1,250 | 1,410 |
| Coastal Sage Scrub | 133,110 | 43,690 | 27,200 | 70,890 | 19,740 | 42,480 | 62,220 |
| TOTAL | 140,770 | 48,560 (34%) |
28,510 (20%) |
77,070 (55%) |
19,940 (14%) |
43,760 (31%) |
63,700 (45%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described below under Data Characterization, 34 of the 70 recent point localities have a high location precision. Of these 34 point localities, 14 will be inside the Criteria Area or Public/Quasi-Public Lands. A total of 20 point localities will be outside of the MSHCP Conservation Area or within Rural/Mountainous designations. Conservation of this species will be considered from a landscape perspective, as discussed above because the species has well defined habitat requirements. Additionally, there are definable locations of Core Areas for focusing conservation efforts where the species is observed in larger numbers.
The conserved Core Areas include the suitable and occupied habitat within the Criteria Area and Public/Quasi-Public designations in the Chino Hills (Proposed Extended Existing Core 1; 270 acres), Badlands (Proposed Core 3; 24,920 acres), Box Springs Mountains (Existing Noncontiguous Habitat Block A plus proposed Constrained Linkages 7 and 8; 4,000 acres), Lake Mathews-Estelle Mountain Reserve (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres), Alberhill (Subunit 2 of Elsinore Area Plan; 3,460 acres), Motte-Rimrock Reserve (Proposed Noncontiguous Habitat Block 4; 1,150 acres), Lake Perris/Bernasconi Hills (Existing Core H; 17,470 acres), Lake Skinner (Existing Core C plus Proposed Extension of Existing Cores 5, 6, 7; 29,060 acres), Vail Lake (Subunit 3 of Southwest Area Plan; 12,320 acres), Wilson Valley (Subunit 2 of REMAP Area Plan; 33,540 acres), and Aguanga (Subunit 4 of REMAP Area Plan 2,660 acres). The total acreage of Core Areas within Criteria Area and Public/Quasi-Public Lands is 152,560 acres. Some additional locations of cactus wrens will be conserved within the Sycamore Canyon Regional Park, Cactus Valley, and Bautista Creek.
The Chino Hills Core Area continues into Orange County where the population also occurs. The Badlands Core Area is located in the vicinity of Lamb Canyon Road and continues north along Gilman Hot Springs Road. The Lake Perris Core Area is within the low hills between the San Jacinto Wildlife Area and Mystic Lake and within the Bernasconi Hills. The Lake Mathews-Estelle Mountain Reserve Core Area is predominantly south of Cajalco Road. The Vail Lake/Wilson Valley Core Area occurs within a broad expanse from east of Vail Lake into the Wilson Creek area, along Sage Road, and north within Wilson Valley. The Aguanga Core Area is within the Temecula Creek drainage south of State Route 79.
Conservation of the cactus wren also requires species-specific conservation measures due to the low abundance of the species within the Plan Area and the specific habitat requirements which include large patches of cactus used for breeding and foraging. Recently, there have been examples within southern California of cactus wren population declines from the destruction of large patches of cactus by fire (Bontrager et al. 1995). These populations of the cactus wren have not recovered well. The species-specific conservation measure for the cactus wren consists of conserving the microhabitat for this species which is composed of cactus patches within the Core Areas within the MSHCP Conservation Area via a number of methods that may include fire suppression (Proudfoot et al. 2000), enhancement, or revegetation with cacti.
Several large blocks of habitat supporting the current known nesting and foraging locations, and potential foraging and nesting locations of the cactus wren will be conserved as Criteria Area and Public/Quasi-Public categories, including the Chino Hills, Badlands, Box Springs Mountains, Alberhill, Lake Mathews-Estelle Mountain Reserve, Motte-Rimrock Reserve, Lake Perris/ Bernasconi Hills, Lake Skinner, Vail Lake, Wilson Valley, and Aguanga. Additional areas that may have isolated cactus wren locations that may or may not be extant, but that may provide potential habitat, include the Santa Rosa Plateau Nature Reserve where a low precision point is located, Prado Basin, Santa Ana River, Fresno Canyon Creek, Bautista Creek, and Cactus Valley. As identified above, the species occurs within the MSHCP Plan Area as a nesting, foraging, and wintering species, and, as such, the MSHCP Conservation Area will provide adequate habitat for all phases of the life history. Habitat containing potential nest sites with adequate protection around each nest site will also be conserved. These MSHCP Conservation Area locations are linked as well, providing dispersal connections between the southern locations at Aguanga and eastern Temecula Creek into San Diego County, along Temecula Creek into the Cleveland National Forest and Santa Rosa Plateau, north from Wilson Valley to the Lake Skinner/Diamond Valley Lake area, north along Bautista Creek into the Badlands and then into San Bernardino County or to Lake Perris area or the Box Springs area. Linkages are provided from Lake Skinner to the Sedco Hills through the Tucalota and Warm Springs drainages and the AD161 Mitigation Area. Habitat patches are then connected to the Santa Ana River via the Sedco Hills and Temescal Wash. Most of these linkages are connected by patches of coastal sage scrub except for those along the drainages which are currently constrained but provide riparian habitat for use as dispersal habitat. The cactus wren is a relatively sedentary species, thus conservation of its preferred habitat with a focus on the microhabitat is very important (Garrett and Dunn 1981). However, vagrants have been observed away from known breeding areas in other regions, consequently, the MSCHP Conservation Area design will provide for connections between Core Areas to provide for the potential for movement of this species (Garrett and Dunn 1981).
In summary, conservation for this species will be achieved by inclusion of at least 77,070 acres of suitable Conserved Habitat and 11 of 12 Core Areas within large blocks of habitat in the MSHCP Conservation Area. In addition, 14 recent and high precision locations will be inside the Criteria Area or Public/Quasi-Public Lands, all of which are recorded for the suitable habitat of the cactus wren. Conservation also will be provided for the habitat linkages between Core Areas as identified above. Additionally, the species-specific conservation measure for the cactus wren consists of conserving the microhabitat for this species which is composed of cactus patches within the Core Areas within the MSHCP Conservation Area. The current population size of the cactus wren is unknown but has been estimated at 100 to 110 pairs (McKernan 1998 pers. comm.).
The Incidental Take of the cactus wren is difficult to quantify due to our limited knowledge of its distribution and abundance within the Plan Area. The maximum level of Incidental Take of cactus wrens can be anticipated by the loss of the number of acres of potential habitat that will become unsuitable for this species. About 63,700 acres (45 percent) of potential habitat for the cactus wren will be outside the Criteria Area and Public/Quasi-Public designations, and individuals within this habitat will be subject to Incidental Take consistent with the plan. Of this, approximately 19,940 acres of potential habitat (14 percent) are located within Rural/Mountainous designation areas. While the Rural/Mountainous areas are not included within the MSHCP Conservation Area, will not be managed for the benefit of wildlife, and the existing zoning/ordinances for these areas do not preclude development and could allow substantial fragmentation and/or degradation of habitat for proposed covered species, the anticipated levels of development of these areas may be consistent with maintaining some habitat for the cactus wren. A total of 20 locations within the UCR database of the cactus wren will be outside the Criteria Area and Public/Quasi-Public designations, 9 of which are located within residential or developed areas and may no longer be extant. The Core Area within the Temecula Creek area west of Vail Lake is not considered conserved. Although a Proposed Constrained Linkage is located within this drainage, the upland areas within which the cactus wren might be present are not conserved.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature. The location database for the cactus wren includes approximately 75 data records from 1888 to 1999. Of these records, approximately 70 are relatively recent (within the past 10 years) and of these, 34 are of high precision and may be accurately located within the Plan Area. Approximately 10 of these high precision records are located within developed areas and although they may no longer exist, they may also represent an observation of a cactus wren within a localized patch of cactus that is within near proximity of a residential development. The rest occur within non-native grassland, sage scrub, chaparral, and other vegetation communities that are likely located within cactus-dominated patches of coastal sage scrub that may be mapped within other vegetation types. The database does not identify those records that are breeding locations or indicate the overall population size.
A low to moderate amount of literature is available for the cactus wren because of its interesting habitat use and natural history. Most of the literature pertains to general natural history, niche determination, and detailed information regarding the nest structure. Few controlled scientific studies have been conducted; however, some management studies are available. Very little information is available for the Plan Area other than what is generally available regarding basic distribution information.
The cactus wren is an obligate, nonmigratory resident of the coastal sage scrub plant community (as defined by Westman 1983 and O'Leary 1990). It frequents deserts and other arid terrain with thickets, patches, or tracts of larger, branching cacti, stiff-twigged, thorny shrubs, and small trees (Grinnell and Miller 1944). In other areas, it is considered an inhabitant of the Chihuahuan, Mojave, and Sonoran deserts and Tamaulpais thorn-shrub communities. It may also be considered a resident of scrubby flats, cactus and mesquite lowland areas, brushy mesas, gulches, hills, and canyons in Texas, desert riparian, creosote bush and large arroyos in Nevada (Proudfoot et al. 2000). It is closely associated with three species of cacti and occurs almost exclusively in thickets of cholla (Opuntia prolifera) and prickly pear (Opuntia littoralis and Opuntia oricola) dominated stands of coastal sage scrub below 457 meters in elevation on mesas and lower slopes of the coast ranges (Proudfoot et al. 2000). Although it lives over a wide range from Texas to the Pacific ocean, it is limited to regions with thorny shrubs and trees that offer nesting sites (Terres 1980).
Characteristic shrubs associated with habitat occupied by the cactus wren and within the coastal sage scrub community include California buckwheat (Eriogonum fasiculatum), coastal sagebrush (Artemisia californica), several sages (Salvia spp.) and scattered shrubs approaching tree-size, such as laurel sumac (Malosma laurina), and lemonadeberry (Rhus integrifolia) (Garrett and Dunn 1981, Unitt 1984, Rea and Weaver 1990). Thickets of xeric vegetation may provide cover and thermal relief. The nest is also used as a roost site (Anderson and Anderson 1957).
The cactus wren is a resident species from southern California south to southern Baja California, southern Nevada, southwestern Utah, western and south central Arizona, southern New Mexico, and central Texas south to Mexico (Terres 1980).
Zeiner, et al. (1990) summarize the distribution, abundance, and seasonality of the cactus wren in California as follows. It is a locally common resident in the Mojave and Colorado deserts, north from the Mexican boundary to Inyo and Kern counties. The coastal race is found in arid parts of westward-draining slopes from San Diego County northwest to Ventura County. It frequents desert succulent shrub, Joshua tree, and desert wash habitats. Historically, cactus wrens within coastal areas were found on the coastal slopes and lowlands of southern California in arid and semiarid regions with abundant cacti (Grinnell 1898, Grinnell and Miller 1944 Unitt 1984). As early as 1944, authorities noted that loss of habitat had greatly reduced the historic range of this species (Grinnell and Miller 1944).
The cactus wren is found at few locations within the Plan Area. It has been recorded along the eastern flank of the Santa Ana Mountains from the vicinity of Corona to Lake Mathews and Alberhill. It also occurs from the city of Riverside east to the Box Springs Mountains and into the Badlands. Small populations also occur in the central portion of the area and Bernasconi Hills near Lake Perris and then disjunctly within the southern portion from Temecula to Aguanga. About 100 to 110 pairs of the cactus wren are estimated to occur in Riverside County (McKernan 1998 pers. comm.).
The Core Areas within the Plan Area consist of a few, small, disjunct populations. Based on the information from Cooper (2001) and the UCR database, as well as the information identified above, the Core Areas are located at the Badlands, Box Springs Mountains, Lake Mathews-Estelle Mountain Reserve, Motte-Rimrock Reserve, Lake Perris area including Bernasconi Hills, Lake Skinner, Vail Lake, Wilson Valley, Aguanga, and Temecula area. These areas appear to be remaining strongholds for low to moderate numbers of the cactus wrens in western Riverside county. The locations of the cactus wren become even more patchy within the central and eastern areas of the county. A Core Area is located within the northwestern section of the county near the Chino Hills adjacent to Orange County where cactus wrens are known to occur within oil fields that have suitable habitat (McKernan 1998 pers. comm.).
Genetics: The variation in plumage patterns and characters are used to distinguish the subspecies of the cactus wren. Eight subspecies are recognized with the subspecies falling into roughly two groups the affinis group (peninsular forms) and brunneicapillus group (continental forms) (Proudfoot et al. 2000). The range of C. b. cousei is now geographically disjunct from interior desert populations as a result of urbanization of the corridor along the San Gorgonio Pass in Riverside County (Rea and Weaver 1990).
Diet and Foraging: The cactus wren forages on the ground and in low vegetation for insects and other small invertebrates, cactus fruits and other fruits, seeds and nectar (Bent 1968; Anderson and Anderson 1973). Fruits make up 15-20 percent of the annual diet, which is more than most North American wrens (Ehrlich, et al. 1988). Foraging behavior is often regulated by heat stress (Ricklefs and Hainsworth 1968), necessitating retreat from exposed sites into shade of shrubs and trees. The cactus wren generally forages on the ground, turning over fallen leaves and other debris in search of insects. It also searches bushes and probes tree bark housing insects. Foliage-gleaning may increase with insect abundance and habitat complexity (Proudfoot et al. 2000).
Daily Activity: The cactus wren exhibits year-long, diurnal activity. The species is not migratory (Zeiner, et al. 1990).
Reproduction: For the cactus wren, thickets of vegetation provide cover and shelter, and the nest, which is usually located in cactus, is used as a roost site as well as for breeding. The nest is usually built in cholla or other large, branching cactus, in yucca, or in a stiff-twigged, thorny shrub or small tree. The nest is an intricate, woven cylinder, usually placed horizontally 1.2 to 1.5 meters (4-5 feet) above the ground (Anderson and Anderson 1957). The large, globular chamber of the nest is about 18 centimeters in diameter with a tunnel-shaped passageway about 9 centimeters in diameter with as much as 30 centimeters between the back wall of the nest chamber and the entrance opening. The mouth of the entrance is usually about 7 centimeters above the base of the chamber. Because the passageway is too small to admit a flying bird, a doorstep or perch is required near the entranceway (Proudfoot et al. 2000). It breeds from March into June. The clutch size is 4-5 eggs, with a range of 3-7 eggs (Harrison 1978). Two broods per season is common. Incubation is 15-18 days, by the female only (Anderson and Anderson 1960). The altricial nestlings fledge at 17-23 days, with an average of 21 (Hensley 1959, Anderson and Anderson 1960). The young may return to roost in the nest after fledging. The young become independent at about 1 mo after leaving the nest; sometimes the young help feed the young of later broods (Harrison 1978).
Survival: Anderson and Anderson (1973) report an overall adult survival rate of 50.6 percent during a six year study. One banded adult was retrapped when it was 4 years old (Terres 1980).
Dispersal: The species is generally considered to have low dispersal capabilities but there is little information available (Ogden Environmental and Energy Services 1993). In Arizona, of 55 nestlings banded, 41 dispersed from the natal site by 45 days postfledging. Males remain near the natal site, usually dispersing only as far as parental territorial behavior dictated (Proudfoot et al. 2000).
Socio-Spatial Behavior: The home range may be the same as the territory (Anderson and Anderson 1963). The average territory was 1.9 hectares (4.8 acres), varying from 1.2-2.8 hectares (2.9-6.9 acres), in Arizona (Anderson and Anderson 1973). The cactus wren may maintain its territory year-round (Anderson and Anderson 1963).
Community Relationships: Domestic cats, roadrunners, snakes, and loggerhead shrikes prey on adults and nestlings (Anderson and Anderson 1973). Austin, et al. (1972) observed nestling predation by gopher snakes and whipsnakes. Frequent interactions with curve-billed thrashers have been reported by Anderson and Anderson (1963), including destruction of cactus wren roosting nests by thrashers.
Continued threats to the cactus wren include habitat loss and fragmentation from urbanization and agricultural development. Domestic cats, roadrunners, snakes, and loggerhead shrikes prey on adults and nestlings (Anderson and Anderson 1973). Cactus wrens that are confined to isolated patches of habitat in urbanizing areas are subject to increased levels of predation pressures as larger predators are replaced by greater population levels of smaller predators and domestic animals. This species is especially vulnerable to stochastic events, especially wildland fires. Because of its narrow habitat requirements, sedentary behavior, and low dispersal characteristics, cactus wrens are subject to loss by fires and, if they disperse, may not find suitable habitat to survive. Intense fires may actually kill cactus plants and eliminate habitat for the cactus wren. As a result of competition from invasive plant competition, grazing, weather patterns and other natural and human-influenced disturbances, the reestablishment of cactus patches essential to this species may take many years. An increasing pattern of habitat fragmentation and isolated populations also diminishes the dispersal ability and inter-population connections of the cactus wren and reduces the overall genetic viability of the species (Ogden Environmental and Energy Services 1993).
The cactus wren is highly associated with cactus thickets in coastal sage scrub and is reliant on cacti for nesting, breeding and foraging. This species has an affinity for cholla cactus as a nesting and roosting site and this plant species is very important to its survival. (Bailey 1922; Grinnell and Miller 1944; Bent 1968; Anderson and Anderson 1973; Root 1988). The recommendations for protecting the cactus wren includes protection and maintenance of large blocks of coastal sage scrub through fire suppression (Rea and Weaver 1990).
Cactus wrens build four to six nests within their territories and thus enumerating the number of nests within an area is not a representative method for sampling population size (Anderson and Anderson 1973).
The cactus wren has been documented to have significant differences in clutch size, breeding success, and the timing of clutch initiation between years (Marr and Ratt 1983). These differences appear to be related to the annual differences in the abundance and emergence of the major food of the nestlings. Long-term temperature patterns may provide a predictor for high prey populations (Marr and Raitt 1983).
A flowchart was developed for the habitat suitability model for the cactus wren (Short 1985). Suitable habitat is evaluated as including: arid savanna, open thorn forest, or semidesert cactus and deciduous tree cover types in southwestern United States; a block of appropriate habitat that is at least 0.4 hectare in area; habitat structure that provides potential nest sites 0.9 to 4.3 meters above ground; types of vegetation that vary in utility as nest sites for the cactus wren; with the density of mid-story vegetation that may modify the utility of habitats for cactus wrens.
Anderson, A. H., and A. Anderson. 1957. Life history of the cactus wren. Part I: Winter and pre-nesting behavior. Condor 59:274-296.
Anderson, A. H., and A. Anderson. 1960. Life history of the cactus wren. Part III: The nesting cycle. Condor 62:351-369.
Anderson, A. H., and A. Anderson. 1963. Life history of the cactus wren. Part IV: Competition and survival. Condor 65:29-43.
Anderson, A.H. and A. Anderson, 1973. The Cactus Wren. The University of Arizona Press, Tucson, Arizona.
Austin, G. T., E. Yensen, and C. S. Tomoff. 1972. Snake predation on cactus wren nestlings. Condor 74:492.
Bailey, F.M. 1922. Cactus wrens' nests in southern Arizona. Condor 24:163-168.
Bent, A.C. 1968. Life histories of North American Nuthatches, Wrens, Thrashers, and their allies. U.S. National Museum Bulletin 195. U.S. Government Printing Office. Washington, D.C.
Bontrager, D. R., R. A. Erickson, and R. A. Hamilton. 1995. Impacts of the October 1993 Laguna Canyon fire on California Gnatcatchers and Cactus Wrens. Pp. 69-76 In Brushfires in California wildlands: ecology and resource management (J. E. Keeley and T. Scott, eds.). Int. Assoc. Wildland fire, Fairfield, WA.
Cooper, D. 2001. California Important Birding Areas. Audubon California, Los Angeles.
Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder's handbook. Simon and Schuster, New York. 785pp.
Garrett, K. and J. Dunn. 1981. Birds of southern California: status and distribution. Artesan Press, Los Angeles, CA.
Grinnell, J. 1898. Birds of the Pacific slope of Los Angeles County.
Grinnell, J. and A.H. Miller. 1944. The distribution of the birds of California. Pacific Coast Avifauna 27.
Harrison, C. 1978. A field guide to the nests, eggs and nestlings of north American birds. W. Collins Sons and Co., Cleveland, OH. 416pp.
Hensley, M. M. 1959. Notes on the nesting of selected species of birds of the Sonoran Desert. Wilson Bull. 71:86-92.
Marr, T.G. and R.J. Raitt. 1983. Annual variations in patterns of reproduction of the cactus wren (Campylorhynchus brunneicapillus). Southwestern naturalist 28:149-156.
McKernan, Robert. 1998. San Bernardino Natural History Museum. Personal communication.
O'Leary, J. F. 1990. California coastal sage scrub: general characteristics and considerations for biological conservation. Pp. 24-41 in Endangered Plant Communities of southern California. Southern California Botanists Special Publication No.3 (A.A. Schroeder, ed.)
Ogden Environmental and Energy Services. 1993. Population viability analysis for the coastal cactus wren within the MSCP Plan Area. Prepared for the Clean Water Program City of San Diego. 16 pp.
Proudfoot, G. A. , D. A. Sherry, and S. Johnson. 2000. Cactus wren (Campylorhynchus brunneicapillus) No. 558. In The Birds of North America, A. Poole and F. Gill, Eds. Cornell laboratory of Ornithology, New York, and The Academy of Natural Sciences, Washington D.C.
Rea, A.M. and K. L. Weaver, 1990. The taxonomy, distribution, and status of coastal California cactus wrens. Western Birds 21: 81-126.
Ricklefs, R. E., and F. R. Hainsworth. 1968. Temperature dependent behavior of the cactus wren. Ecology 49:227-233.
Root, T. 1988. Atlas of wintering North American birds. An analysis of Christmas bird count data. University of Chicago Press, Chicago IL.
Short, H. L. 1985. Habitat suitability index models: cactus wren. U.S. Fish and Wildlife Service Biological Report 82(10.96).
Termes, J. K. 1980. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf, New York, New York. 1109pp.
Unitt, P. 1984. The Birds of San Diego County. San Diego Society of Natural History, San Diego, CA.
Westman, W. E. 1983. Factors influencing the distribution of species of California coastal sage scrub. Ecology 62: 439-455.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
California horned lark (Eremophila alpestris actia)
State: Species of Special Concern
Federal: none
The California horned lark is relatively widely-distributed throughout the MSHCP Plan Area within its suitable habitat, however, it is not predictably distributed within all suitable areas. It occurs in some of the sparsely vegetated habitats but has not been documented to be uniformly distributed within all open habitat areas. There appear to be several Core Areas including Mystic Lake/San Jacinto Wildlife Area, the grasslands within Prado Basin, Wasson Canyon area, Moreno Valley/March ARB, and Murrieta/Murrieta Hot Springs area. Because it is well known for using open, sparsely vegetated habitats but has specific locations that appear to be Core Areas, it responds well to a landscape level of management with site specific requirements.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 153,750 acres of suitable foraging and nesting habitat for the California horned lark including playa and vernal pool habitats, agriculture (field croplands), grassland, cismontane alkali marsh, coastal sage scrub, and Riversidean alluvial fan sage scrub. The scrub habitats provide foraging habitat and nesting opportunities in areas where the scrub is relatively sparse.
Include within the MSHCP Conservation Area at least 3 Core Areas and a portion of a fourth Core Area for the California horned lark including grasslands around Prado Basin (including the adjacent Santa Ana River area; 9,670 acres), Wasson Canyon (Subunit 5 of Elsinore Area Plan; 2,320 acres), Mystic Lake/San Jacinto Wildlife Area (Subunit 4 of Reche Canyon/Badlands Area Plan; 2,690 acres), and a portion of the Core Area in the Murrieta/Murrieta Hot Springs area (Proposed Core 2; 5,050 acres). Other locations are conserved as well, although they may not include Core Areas. These other locations include Lake Elsinore grasslands, Santa Rosa Plateau, and Wilson Valley.
The California horned lark uses predominantly open land including agriculture, grassland and playas for foraging as well as sparse shrub and scrub habitats (Garrett and Dunn 1988). The California horned lark breeds, winters ,and migrates throughout the MSHCP Plan Area. For the purpose of the conservation analysis, potential habitat for the California horned lark includes agriculture(field croplands), grassland, cismontane alkali marsh, playa and vernal pool habitat, Riversidean alluvial fan sage scrub, and coastal sage scrub. The scrub habitats are included because they have been recorded foraging and nesting within sparse forms of such habitats and constitute of a Core Area within the scrub habitat in the Wasson Canyon area. The horned lark has been recorded using chaparral and riparian habitat, however these are not typical habitats used by the species. The observation may have been of the species foraging nearby and thus these habitats are not included in the analysis. The habitats included in the analysis comprise open habitat within which they typically forage and nest. Based on these habitats, the Plan Area supports approximately 438,550 acres of potential habitat for the California horned lark. Table 1 shows the conservation and loss of potential habitat for the California horned lark. Overall, approximately 153,750 acres (35 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public Lands.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
CALIFORNIA HORNED LARK
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| All Bioregions | |||||||
| Agriculture Land (field crops) | 230,370 | 7,250 | 9,940 | 106,590 | 820 | 105,770 | 106,590 |
| Grassland | 146,870 | 20,010 | 22,810 | 42,820 | 12,220 | 91,830 | 104,050 |
| Cismontane Alkali Marsh | 150 | 40 | 0 | 40 | 0 | 110 | 110 |
| Playas and Vernal Pools | 7,910 | 3,830 | 2,920 | 6,750 | 0 | 1,160 | 1,160 |
| Riversidean Alluvial Fan Sage Scrub | 7,150 | 3,170 | 2,060 | 5,230 | 220 | 1,700 | 1,920 |
| Coastal Sage Scrub | 152,690 | 47,160 | 34,560 | 81,720 | 26,240 | 44,730 | 70,970 |
| TOTAL | 438,550 | 81,460 (19%) |
72,290 (16%) |
153,750 (35%) |
39,500 (9%) |
245,300 (56%) |
284,800 (65%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described above under Data Characterization, 77 of the 187 recent point localities have a high location precision of "1." Of these 77 point localities, 34 will be inside the Criteria Area or Public/Quasi-Public Lands. A total of 43 point localities will be outside of the MSHCP Conservation Area, 25 percent of which are within residential/developed areas. Three of the five core population areas where the species is observed, (including the adjacent Santa Ana River area; 9,670 acres), Wasson Canyon (Subunit 5 of Elsinore Area Plan; 2,320 acres), Mystic Lake/San Jacinto Wildlife Area (Subunit 4 of Reche Canyon/Badlands Area Plan; 2,690 acres) will be conserved. A fourth Core Area, the Murrieta/Murrieta Hot Springs area, will be conserved in part within the Proposed Core in the Antelope Valley area in the form of the scrub areas north of Clinton Keith Road east to French Valley, the Hogbacks, and east into the AD161 mitigation area (Proposed Core 2; 5,050 acres). Conservation of this species will be considered from a landscape perspective because the species is very flexible and opportunistic for its foraging requirements. Additionally, there are definable locations for focusing conservation efforts where the species is observed in larger numbers within Core Areas. A total of 19,730 acres of Core Areas will be conserved within large habitat blocks of a minimum size of 2,320 acres.
Several large blocks of habitat supporting the current known and potential foraging and nesting locations of the California horned lark will be conserved as Criteria Area and Public/Quasi- Public lands, including the Prado Basin, Mystic Lake/San Jacinto Wildlife Area, Proposed Core in the Antelope Valley area, and Wasson Canyon. Additional large blocks that contain observations and that provide potential nesting and foraging habitat include Wilson Valley, Santa Rosa Plateau Nature Reserve, and Lake Elsinore grasslands. As identified below, the species occurs within the MSHCP Plan Area as a breeding and wintering resident and as such, the MSHCP Conservation Area will provide adequate habitat for foraging and nest sites. These MSHCP Conservation Area areas are linked as well, however the California horned lark, due to its ability to move long distances, may rely less on the linkages than other species.
In summary, conservation for this species will be achieved by the inclusion of at least 153,750 acres of suitable Conserved Habitat and the Core Areas within the Prado Basin, Wasson Canyon, and Mystic Lake/San Jacinto Wildlife Area, as well as a portion of the Core Area within the Murrieta/Murrieta Hot Springs area (Proposed Core 2). The current population size of the California horned lark is unknown however the foraging and nesting habitat requirements are well defined. The species is moderately predictable in its occurrence and may vary in number within the area from a few to many individuals. It occurs repeatedly in a number of conserved locations.
About 284,800 acres (65 percent) of potential habitat for the California horned lark will be outside the Criteria Area and Public/Quasi-Public designations and individuals within these areas will be subject to Incidental Take consistent with the Plan. One of the 5 Core Areas, the Moreno Valley/March ARB area, will be outside the MSHCP Conservation Area. A portion of a Core Area within the Murrieta/Murrieta Hot Springs area will be outside the MSHCP Conservation Area.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The UCR location database includes approximately 252 records for the California horned lark dated from 1887 to 1999. Approximately 187 of these data records are recent (within the past 10 years) and of these recent records, approximately 77 are of high precision and suitable for analysis. The habitat types associated with these data records are varied: from sage scrub, grassland, chaparral, riparian scrub and willow riparian, alkali playa to more developed habitats including crop lands and residential. Occurrence within residential does not necessarily indicate the species record is no longer extant because this species may occur opportunistically within its wintering habitat.
The literature available for this species is low to moderate with several general to detailed natural history summaries within the ornithological reference literature. A few controlled scientific studies have been conducted within the physiological ecology literature.
The California horned lark is a common to abundant resident in a variety of open habitats, usually where trees and large shrubs are absent (Zeiner, et al. 1990). In the Midwest, the species has been characterized as the most abundant species in row-crop fields (Best, et al. 1998). Range-wide, California horned larks breed in level or gently sloping shortgrass prairie, montane meadows, "bald" hills, open coastal plains, fallow grain fields, and alkali flats (Grinnell and Miller 1944). In nonagricultural lands, it typically inhabits areas of short vegetation or bare ground, including shortgrass prairie, deserts, brushy flats, and alpine habitat. In shrubsteppe habitats, it occupies areas characterized by low vegetation. Within southern California, California horned larks breed primarily in open fields, (short) grasslands, and rangelands (Garrett and Dunn 1981; Hamilton and Willick 1996). Grasses, shrubs, forbs, rocks, litter, clods of soil, and other surface irregularities provide cover.
The horned lark has a holarctic distribution, ranging from the Arctic south to central Asia and Mexico with outlying populations in Morocco and Colombia. In general, the northernmost populations are migratory, moving south during the winter into remaining areas of the breeding range. There are also southward movements into areas south of the breeding range, particularly in the southeastern United States (Beason 1995).
The horned lark has increased dramatically in the Midwest and eastern North America from the late 1800s to early 1900s. This expansion has coincided with the deforestation and the creation of agricultural fields and grassland which are good nesting habitat for the horned lark. The species has also shown a southward range expansion between 1900 and 1910 into Kentucky and the Ozark Mountains and then into Oklahoma by the 1920s (Beason 1995).
The California horned lark breeds and resides in the coastal region of California from Sonoma County southeast to the United States/Mexican border, including most of the San Joaquin Valley, and eastward to the foothills of the Sierra Nevada (Grinnell and Miller 1944; AOU 1998). Zeiner, et al. (1990) summarize the distribution, abundance, and seasonality as follows. It is a common to abundant resident in a variety of open habitats, usually where trees and large shrubs are absent. It is found from grasslands along the coast and deserts near sea level to alpine dwarf-shrub habitat above tree line. It is less common in mountain regions, on the north coast (McCaskie, et al. 1979), and in coniferous or chaparral habitats. It mostly leaves the mountains in the winter, but small flocks may remain to winter on windswept, snow-free areas at high elevations in the Sierra Nevada (Gaines 1977). In winter, flocks in desert lowlands and other areas are augmented by winter visitants, many migrating from outside the state (Garrett and Dunn 1981). It is a resident on the Channel Islands (Garrett and Dunn 1981). It is a year-long resident within the state. After breeding, it becomes very gregarious; it often forms large flocks that forage and roost together. Migrants from outside of California join these wintering flocks, especially in the southeastern desert region of the state. Migrant status on the Farallon Islands indicates a latitudinal movement along the coast as well (DeSante and Ainley 1980).
The California horned lark apparently occurs throughout much of western Riverside County in suitable habitat. It is broadly scattered throughout the central portion of the Plan Area. The numbers of horned larks in southern California are greatly augmented in winter by birds from outside the region (Garrett and Dunn 1981). Generally, the species occurs scattered throughout the lower elevations of the MSHCP Plan Area from Prado Basin, south along the Interstate 15 corridor to Temecula, up into the Santa Rosa Plateau, all along the Interstate 215 corridor, the hills and scrub area between the two freeways, then east to the Badlands, south to Vail Lake/Wilson Valley, sparsely in the Badlands and in the Beaumont/ Banning area. It also occurs sparsely within the mountain Bioregions of the Plan Area.
California horned larks are apparently most heavily concentrated in the Prado Basin, Wasson Canyon area, Moreno Valley and March ARB area, Murrieta/ Murrieta Hot Springs area, and Mystic Lake/San Jacinto Wildlife Area (Hays, 1999, pers. obs.; Patten, 1998, pers. comm.). Additional scattered geographic locations recorded within the U.C. Riverside database include: Hemet, Homeland/Lakeview Mountains, Lake Elsinore, Menifee, Rawson Canyon, Reche Canyon, Riverside East, Sage, Temecula/Rancho California, Wildomar, Bautista Creek, San Timoteo Creek, Wilson Creek and Wilson Valley, Diamond Valley Lake, Lake Mathews Reserve, Lake Perris SRA, Lake Skinner, and the Santa Rosa Plateau Nature Reserve.
Genetics: The horned lark species is divided into 21 subspecies in North America by the fifth American Ornithologists' Union check-list with 15 subspecies in western North America. The subspecies are based primarily on differences in plumage coloration and size, with western populations paler and smaller than eastern and northern populations (Beason 1995).
Diet and Foraging: Horned larks feed primarily on grains and other seeds and shift to mostly insects in the summer months (Bent 1942). It mostly eats insects, snails, and spiders during breeding season; it adds grass and forb seeds and other plant matter to the diet at other seasons (Bent 1942). Individuals forage on the ground in either bare areas or in agricultural fields with short vegetation (Beason 1995). In winter, flocks frequent roadsides, feedlots, and fields where manure from feedlots is spread especially when snow cover is heavy. Sometimes it perches on a plant to take seeds from seed heads. It walks along ground, searching for food. Usually, it is moving while it is feeding but it may also remain in one spot for up to five minutes (Beason 1995). It drinks freely from water holes, but individuals have survived in captivity for 16-31 days without water (Airola 1980).
Daily Activity: In the desert, horned larks may spend much of the day standing in the shade of posts and rocks (Beason 1995).
Reproduction: The horned lark builds a grass-lined nest in a depression on the ground in the open. Individuals are monogamous within a breeding season with no long-term pair bonds formed (Beason 1995). The clutch size varies from two to five eggs (Beason 1995). It breeds from March through July, with a peak in activity in May. The pair nests solitarily. It frequently raises 2 broods in a season (Bent 1942). Incubation is 10-14 days; the altricial young are tended by both parents. The young leave the nest at 9-12 days, and can fly 3-5 days later (Harrison 1978).
Survival: The breeding success rate (fledglings per nest) of the horned lark varies from 23 to 72 percent (Beason 1995).
Dispersal: The young horned larks leave the nest, on average, after ten days (Beason 1995). The dispersal distance is not reported.
Socio-Spatial Behavior: Flock size of horned larks range from 5 to 405 birds per square mile with the variability in flock size dependent on season and local environment (Zeiner et al. 1990). Winter flock size is greatly augmented by winter visitors (Zeiner, et al. 1990). Territory size varies from 0.3 to 5.1 hectares depending on population densities and habitat (Beason 1995). Territories are only maintained during the breeding season and give way to formation of flocks during the winter. Verbeek (1967) estimated a typical territory size as 1.6 hectares (4 acres) in Wyoming alpine tundra. In midwestern farmland, the territory is reported as 0.6 to 3.2 hectares (1.5 to 8 acres) (Beason and Franks 1974), 0.4 to 5.3 hectares (1-13 acres) (Pickwell 1931), and 4.9 hectares (12 acres) (Fitch 1958).
Community Relationships: Eggs and nestlings of the horned lark are subject to predation from mammals and snakes. The adults are prey for falcons. It can be parasitized by brown-headed cowbirds during the second breeding (Beason 1995).
Continuing threats to the California horned lark include habitat destruction and fragmentation. In nearby Orange County, habitat destruction has significantly reduced the county's nesting and wintering numbers (Hamilton and Willick 1996). The habitat of the California horned lark is easily converted to other landscapes and human uses. Pesticides, specifically Carbofuran and Fenthion, have been shown to poison and kill horned larks (Beason 1995). A total of 44 percent of nest failures have been attributed to mowing in airport grasslands occupied by horned larks (Kershner and Bollinger 1996).
The Prado Basin population of the California horned lark apparently has remained stable over the course of 14 years of monitoring efforts at that locale (Hays, 1999, pers. obs.).
In the winter, horned larks form large, gregarious, somewhat nomadic groups and may undertake movements to exploit non-uniformly distributed food resources (Beason 1995). Because of the species' use of agricultural fields, the effects of pesticides have been identified as a necessary component of the management of this species (Boutin, et al. 1999). Rangeland alteration activities (removal of shrubs and planting of wheatgrass) in southern Oregon resulted in increased numbers of horned larks after an initial one-year time lag response (Wiens and Rotenberry 1991).
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Airola, D. A., ed. 1980. California wildlife habitat relationships program: Northeast Interior Zone. Vol III. Birds. U.S. Dep. Agric., For. Serv., Lassen Natl. For., Susanville. 590pp.
Beason, R. C., and E. C. Franks. 1974. Breeding behavior of the horned lark. Auk 91:65-74.
Beason, Robert C. 1995. Horned Lark (Eremophila alpestris) In The Birds of North America, No. 195 (A. Poole and F. Gill, eds.) The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists' Union, Washington, D.C.
Bent, A. C. 1942. Life histories of North American flycatchers, larks, swallows, and their allies. U.S. Natl. Mus. Bull. 179. 555pp.
Best, L.B., H. Campa, K. E. Kemp, R. J. Robel, M. R. Ryan, J. A. Savidge, S. R. Winterstein, and H. P. Weeks. 1998. Avian abundance in CRP and crop fields during winter in the Midwest. American Midland Naturalist 139:311-314.
Boutin, C., K. E. Freemark, and D. A. Kirk. 1999. Farmland birds in southern Ontario: Field use, activity patterns and vulnerability to pesticide use. Agriculture Ecosystems & Environment 72: 239-254.
DeSante, D. F., and D. G. Ainley. 1980. The avifauna of the South Farallon Islands, California. Studies in Avian Biol. No. 4. Cooper Ornithol. Soc., Lawrence, KA. 104pp.
Fitch, H. S. 1958. Home ranges, territories, and seasonal movements of vertebrates of the Natural History Reservation. Univ. Kans., Lawrence. Publ. Mus. Nat. Hist. 11:63- 326.
Gaines, D. 1977. Birds of the Yosemite Sierra. California Syllabus, Oakland. 153pp.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Copper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April, 1986. 617 pp.
Hamilton, R. and D.R. Willick. 1996. The Birds of Orange County, California: Status and Distribution. Sea and Sage Press, Irvine, California. 150 pp. with appendices.
Harrison, C. 1978. A field guide to the nests, eggs and nestlings of North American birds. W. Collins Sons and Co., Cleveland, OH. 416pp.
Hays, Loren R. 1999. USFWS, pers. obs.
Kirshner, E.L. and E.K. Bollinger. 1996. Reproductive success of grassland birds at East-central Illinois airports. American Midland Naturalist 136:358-366.
McCaskie, G., P. De Benedictis, R. Erickson, and J. Morlan. 1979. Birds of northern California, an annotated field list. 2nd ed. Golden Gate Audubon Soc., Berkeley. 84pp.
Patten, Michael. 1998. Riverside County Editor for American Field Notes and Past Secretary, California Bird Records Committee, pers. comm.
Pickwell, G. 1931. The prairie horned lark. St. Louis Acad. Sci. Trans. 27:1-153.
Verbeek, N. A. M. 1967. Breeding biology and ecology of the horned lark in alpine tundra. Wilson Bull. 79:208-218.
Wiens, J.A. and J. T. Rotenberry. 1991. Response of breeding passerine birds to rangeland alteration in a North American shrubsteppe locality. Journal of Applied Ecology, v.22, n.3: 655-668.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
California spotted owl (Strix occidentalis occidentalis)
State: Species of Special Concern
Federal: Federal Special Concern species; San Bernardino National Forest Sensitive; Cleveland National Forest Sensitive; Species of Management Concern
The California spotted owl has a sparse distribution within the Santa Ana Mountains, San Bernardino Mountains and San Jacinto Mountains Bioregions of the MSHCP Plan Area within montane coniferous and oak-deciduous woodlands and forest habitats. It is a Group 2 species because its conservation requires integration of habitat protection with site specific monitoring and management.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 41,370 acres of suitable montane coniferous forest and oak deciduous woodland and forest habitats within the Santa Ana Mountains (7,350 acres), San Bernardino Mountains (1,620 acres), and San Jacinto Mountains (32,400 acres) Bioregions for breeding, foraging, wintering use, and dispersal movement for the California spotted owl.
Include within the MSHCP Conservation Area the nesting locations within the Santa Ana, San Jacinto and San Bernardino mountains.
Habitat for the California spotted owl includes oak woodland and forest and montane coniferous forest and within canyons in chaparral covered hillsides where oak woodland is present within the Santa Ana Mountains, San Bernardino Mountains, and San Jacinto Mountains bioregions. This provides not only foraging and nesting habitat in the montane areas where the species has been documented to occur, but also provides winter foraging areas for the species if they move to somewhat lower elevations such as to the Santa Rosa Plateau for some period of time. Based on these habitats, the Plan Area supports approximately 57,370 acres of potential habitat for the California spotted owl. Table 1 shows the conservation and loss of potential habitat for the California spotted owl. Overall, approximately 41,370 acres (72 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public lands.
The California spotted owl occurs within Forest Service lands for nesting within montane coniferous forest and oak woodland and forest habitats. Under the existing Forest Land allocation plan, these locations or habitats are predominantly in the Mt. San Jacinto and Thomas Mountain areas but may also be located within the San Jacinto Wilderness Area as well as the Horse Creek Ridge, Rouse Hill, and Hixon Flat roadless areas in the San Bernardino National Forest, in the Mt. San Jacinto State Park Wilderness (few), and the San Mateo Canyon Wilderness Area (few), Wildhorse and Trabuco roadless areas in the Cleveland National Forest. Within Cleveland National Forest, 90 acres of oak woodland are located within the Tenaja range allotment and 190 acres of oak woodland are located within the Verdugo range allotment. Within the San Bernardino National Forest, 4,090 acres of coniferous and oak woodland are located within the Garner range allotment, 1,140 acres of coniferous and oak woodland are located within the Rouse range allotment and 270 acres of coniferous and oak woodland are located within the Wellman range allotment.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
CALIFORNIA SPOTTED OWL
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| San Bernardino Mountains, San Jacinto Mountains, and Santa Ana Mountains Bioregions | |||||||
| Oak Woodlands and Forests | 27,570 | 1,280 | 19,690 | 20,970 | 4,060 | 2,540 | 6,600 |
| Montane Coniferous Forest | 29,800 | 20 | 20,380 | 20,400 | 40 | 9,360 | 9,400 |
| TOTAL | 57,370 | 1,300 (2%) |
40,070 ( 70% ) |
41,370 (72%) |
4,100 (7%) |
11,900 (21%) |
16,000 (28%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described below under Data Characterization, 5 relatively recent (1987 through 1995) point localities have been documented for the MSHCP Plan Area within the UCR database. The 5 point localities are of too low of precision to determine if they are inside the Criteria Area or on Public/Quasi-Public Lands.
Intensive spring surveys for spotted owls were conducted on the San Jacinto Ranger District of the San Bernardino National Forest between 1988 and 1994, for which the results have not been incorporated into the UCR database. Casual surveys have continued since 1994 as opportunity allows. An average of 10 pairs (range 8-14), 6 singles (range 3-9), and 6 juveniles (ranges 1-10) were reported between 1988 and 1994. Areas where owls have been consistently located include: Hall Canyon, North Fork San Jacinto River, Stone Creek, Logan Creek, Pinewood, Fuller Ridge, Dark Canyon, Strawberry Creek, Marion Creek, Hurkey Creek, South Fork San Jacinto River, and Lion Canyon. These areas support predominantly mixed conifer, riparian hardwood and live oak/big-cone Douglas-fir. Other sporadic sightings or vocal detections have occurred on Thomas Mountain and the northeast side of Baldy Mountain. The San Jacinto Wilderness has been largely unsurveyed but few pair may be present. A few, sporadic surveys of Santa Rosa Mountain and Cahuilla Mountain have not yielded any results, although suitable owl habitat does exist (USFS 1999 pers. comm.). The California spotted owl locations are inside the MSHCP Conservation Area within Public/Quasi-Public lands of the San Bernardino National Forest and nest locations will be conserved. Approximately three locations have been recorded in the Cleveland National Forest, however these locations are outside the Plan Area but may use suitable habitat within the Plan Area (Stephenson and Calcarone 1999).
Additional locations of California spotted owls were obtained from the California Department of Fish and Game (Gould 2002 pers. comm.). These locations were generally documented through 1996 but have been updated to include some additional locations through 1998. The CDFG database indicates there are a total of 22 locations within the San Bernardino National Forest, predominantly within the Mt. San Jacinto and Thomas Mountain areas, with one location north of Banning possibly on private land within the San Bernardino National Forest, and two locations within the Santa Ana Mountains within the Cleveland National Forest.
The Forest Service will need to provide protection for specific nesting site locations and potential nesting sites (i.e., large trees) due to their overall sensitivity to disturbance. There are definable locations for focusing conservation efforts within the Forest Service lands within the San Bernardino National Forest and Cleveland National Forest that are composed of conifer forest, oak woodland forest, and may be interspersed with meadows and grasslands. The Forest Service will also need to address fire management within areas occupied by spotted owls as these areas have not burned during recent times. Timber activities will be addressed with respect to the California owl nesting and foraging habitat.
Known nesting locations, as identified in the previous section, will be conserved as well as habitat potentially supporting the California spotted owl within Criteria Area and Public/Quasi-Public designations, including the montane coniferous and oak woodland habitat within the San Bernardino National Forest, Mt. San Jacinto Wilderness State Park, and Cleveland National Forest. Other areas that are outside of the roadless and wilderness areas may not be so managed. The following large blocks of habitat have not been mapped within the UCR database or by the USFS as containing the California spotted owl: near Santiago Peak in the Cleveland National Forest, Indian Mountain to Poppet Flat, northeastern corner of the Plan Area, area east of Lake Hemet (Spitler Peak and Cone Peak), and Cahuilla Mountain/Red Mountain area. However, these habitat blocks may contain potentially suitable habitat and could be occupied by California spotted owls in the future. As a species with a large foraging area, California spotted owls are likely able to discover and use patches of oak woodland or coniferous habitat that have not been documented to be used in the past. As such, the MSHCP Conservation Area will provide adequate large blocks of habitat as core areas around the currently known nest sites of the species as well as other large blocks of suitable habitat that may be occupied in the future, used for foraging or for wintering.
As depicted on the MSHCP map (Figure 3-1, MSHCP Volume 1), certain areas adjacent to or in proximity to the MSHCP Conservation Area are designated as Rural/Mountainous in the County's General Plan. A total of 4,100 acres (7 percent) of potential breeding habitat will be designated Rural/Mountainous, which will permit 1 DU/10, 20, or 40 acres depending on slope. These areas are generally constrained for development due to steep topography and the level of development in these areas is anticipated to be of a low density, rural residential character. While these areas will not be included within the MSHCP Conservation Area or managed for the benefit of species conserved under the MSHCP, the low levels of development anticipated in these areas will provide an edge to the MSHCP Conservation Area that may be of value to the California spotted owl.
For the California spotted owl, conservation on the Santa Rosa Plateau may be important for maintaining connection between the Santa Rosa Plateau Nature Reserve and the Santa Ana Mountains. MSHCP Conservation Area locations in these areas are generally surrounded by Rural/ Mountainous designations. Potential development in these areas is anticipated to retain vacant areas that will provide for seasonal movement for this species. No nest sites are located within the Rural/ Mountainous designation.
In summary, conservation for this species will be achieved by inclusion of at least 41,370 acres of suitable Conserved Habitat and the known nesting localities within large blocks of habitat in the MSHCP Conservation Area.
Approximately 16,000 acres (about 28 percent) of potential habitat for the California spotted owl will be outside the Criteria Area or Public/Quasi-Public designations, and individuals within these areas will be subject to Incidental Take consistent with the Plan. Approximately five locations from the CDFG database appear to be located outside of the Criteria Area or Public/Quasi-Public designations. Only one of these five locations outside of the MSHCP Conservation Area has been recorded as nesting (1988). No other known nesting areas are outside the Criteria Area or Public/Quasi-Public designations. No take of nesting locations is included within this permit.
Data reviewed includes the University of California, Riverside, GIS database, the California Natural Diversity Data Base (CNDDB), surveys conducted by the San Bernardino National Forest and a database maintained by the California Department of Fish and Game as well as available literature.
The UCR location database includes five records for the California spotted owl within the Plan Area dated from 1987 to 1995. None of the records is of high precision; one is of moderate precision and recorded for chaparral. The history and status of the records is unknown although the locations are likely extant. One record is within Cleveland National Forest near Highway 74, three records are within the San Bernardino National Forest and one is located in Temecula and is of such low precision that it could be located within the Santa Rosa Plateau. The 1999 USFS census information indicates approximately 10 pairs, 6 singles, and 6 juveniles within the San Bernardino National Forest. The locations for these observations are discussed below. Additional information was obtained from the California Department of Fish and Game from a database that records locations and nesting information of the California spotted owl. This database has been kept up through 1996 with a few additional records added through 1998. A total of 22 locations were provided by CDFG.
The literature available on the California spotted owl, as well as the spotted owl as a whole, is relatively large. It is one of the most-studied and best-known owls in the world. This degree of scientific attention is the result of the owl's association with late seral stage conifer forest of high commercial value. The literature is focused on the natural history of the species, and also includes physiological studies, conservation strategies, and management studies for the species. Several general ornithological reference treatments have been prepared for the species and it has been treated within the general raptor literature. A summary of available information as well as a report of the policy implementation team provides substantial information for the species, only a small part of which is presented within this species account (Standiford et al. 1994). Little information is available with respect to the Plan Area other than general distribution and occurrence information.
Other references that provide information include the Report of the Advisory Panel on the Spotted Owl (Dawson et al. 1986), The Report of the Policy Implementation Planning Team (Standiford et al. 1994), and The California spotted owl: a technical assessment of its current status (Verner et al. 1992).
In northern California, the northern spotted owl subspecies resides in dense, old-growth, multi-layered mixed conifer, redwood, and Douglas-fir habitats, from sea level up to approximately 2,300 meters (0-7,600 feet). It requires blocks of 40-240 hectares (100-600 acres) of mature forest with permanent water and suitable nesting trees and snags (Forsman 1976). The northern spotted owl was declared Federally Threatened in June 1990.
In southern California, the California spotted owl occurs at lower elevations (sea level to 1,000 meters), and occupies habitats dominated by hardwoods, primarily oak and oak-conifer woodlands (Garrett and Dunn 1981). At higher elevations, up to 2,700 meters (8,500 feet) they inhabit areas dominated by conifers (Gutiérrez et al. 1995; Stephenson 1991). The nesting and roosting habitats are similar to that of the northern spotted owl. The habitats are generally complex in structure with high canopy closure (Gutiérrez et al. 1995). A critical element of this complex forest structure is the presence of large trees greater than 90 centimeters diameter at breast height. In areas where logging has occurred, many large trees are of advanced age, indicating that a residual old growth or late seral stage element is usually present in the breeding and roosting habitat (Gutiérrez et al. 1995). California spotted owls appear to behave as habitat specialists at the scale of nest habitat selection choosing more complex vegetative structure with greater variation in tree sizes, larger trees, and higher canopy closure (LaHaye et al. 1997). In the Sierra Nevada, the owls did not nest where this residual old-growth component was absent. The foraging habitat appears to be more variable and includes both intermediate-aged and older forested habitats within a home range (Gutiérrez et al. 1995). The forests occupied by the California subspecies are less fragmented than random forest areas (Moen 1994). The species uses dense, multi-layered canopy cover for roost seclusion. The habitats selectively chosen by the California spotted owl are live oak/big-cone Douglas-fir forests (41 percent), riparian/hardwood forests (32 percent), and mixed conifer forests (26 percent) (Verner et al. 1992).
Roost selection appears to be related closely to thermoregulatory needs; the species is intolerant of high temperatures (Weathers et al. 2001). It roosts in dense overhead canopy on north-facing slopes in the summer. In winter, it roosts in oak habitats. In northern regions of the state, daytime roosts averaged 165 meters (549 feet) from water; in southern regions, daytime roosts averaged only 51 meters (173 feet) from water (Barrows and Barrows 1978; Barrows 1981).
The spotted owl species as a whole is distributed in western North America and Mexico. It is fairly evenly distributed throughout the northern part of its range but has a more patchy distribution in southern California, southwestern United States, and Mexico. Its breeding distribution is restricted to forest communities. It is found from sea level to as high as 1,200 meters elevation in the northern part of its range and to about 2,700 meters in the southwestern United States (Gutierrez et al. 1995).
California spotted owls are an uncommon, permanent resident that range from the south Cascade Range and northern Sierra Nevada from Pit River, Shasta County, California south through the remainder of the western Sierra Nevada and Tehachapi Mountains to Lebec, Kern County (Zeiner et al. 1990). The California spotted owl is found sparsely east of the Sierra Nevada crest. It occurs in the California coastal ranges from Monterey County south to Santa Barbara County, then in the Transverse Ranges and Peninsular Ranges south to Sierra San Pedro Martir in northern Baja California (Gutierrez et al. 1995). Its distribution is extremely local and fragmentary in southern California and Mexico.
Zeiner et al. (1990) summarize the distribution, abundance, and seasonality of the spotted owl within California as follows: It is an uncommon, permanent resident in suitable habitat within its range as described above. It may move downslope in winter along the eastern and western slopes of the Sierra Nevada, and in other areas within its distribution. The California spotted owl occurs in all of the major mountain ranges in the southern California national forest lands although some ranges support very few pairs (Stephenson and Calcarone 1999). The California spotted owl within southern California is clustered in disjunct mountain and foothill areas where suitable habitat exists and these clusters are generally surrounded by large areas of unsuitable habitat (Stephenson and Calcarone 1999).
A minimum of 3,050 individuals have been detected between 1970 and 1992 within the range of the California spotted owl. A total of 1,008 pairs and 436 single birds are known to occur in the Sierra Nevada and 598 individuals are known from 15 other populations (Gutierrez et al. 1995). The potential population size of the California spotted owl in southern California has been estimated to be potentially 578 pairs (estimated from CDFG database; Standiford et al. 1994). The largest subpopulation of the California spotted owl within the southern California area is the 200-plus territories in the San Bernardino and San Gabriel mountains. Although Cajon Pass separates these two mountain ranges, there is not a major habitat discontinuity and only six miles separate the easternmost San Gabriel territory from the westernmost San Bernardino territory (Stephenson and Calcarone 1999).
Historical distribution is presumed to be the same as the current distribution, although the numbers of individuals may have declined within certain areas and habitats (Gutierrez et al. 1995).
California spotted owls in western Riverside County are found within high-elevation coniferous and hardwood forest areas primarily within Forest Service lands in the San Jacinto Mountains and Palomar Range. It also occurs in the San Bernardino Mountains and the Santa Ana Mountains (Stephenson and Calcarone 1999; Garrett and Dunn 1981).
Low precision geographic locations recorded within the U.C. Riverside database include: Santa Rosa Plateau East, Cleveland National Forest near Highway 74 and San Bernardino Forest near or within the San Jacinto Wilderness area and near Lake Fulmor.
Intensive spring surveys for spotted owls were conducted on the San Jacinto Ranger District between 1988 and 1994. Casual surveys have continued since 1994 as opportunity allows. An average of 10 pairs (range 8-14), 6 singles (range 3-9), and 6 juveniles (ranges 1-10) were reported between 1988 and 1994. Areas where owls have been consistently located include: Hall Canyon, North Fork San Jacinto River, Stone Creek, Logan Creek, Pinewood, Fuller Ridge, Dark Canyon, Strawberry Creek, Marion Creek, Herkey Creek, South Fork San Jacinto River, and Lion Canyon. These areas support predominantly mixed conifer, riparian hardwood and live oak/big-cone Douglas-fir. Other sporadic sightings or vocal detections have occurred on Thomas Mountain and the northeast side of Baldy Mountain. The San Jacinto Wilderness has been largely unsurveyed. A few, sporadic surveys of Santa Rosa Mountain and Cahuilla Mountain have not yielded any results, although suitable owl habitat does exist (USFS pers. comm. 1999).
Genetics: There are three recognized subspecies: northern spotted owl, California spotted owl, and Mexican spotted owl. The Mexican subspecies is a distinguishable taxon based on allozyme electrophoresis. The analysis of mtDNA sequences shows strong differentiation among currently recognized subspecies, suggesting that the current taxonomy is valid (Gutierrez, et al. 1995).
Diet and Foraging: The spotted owl feeds in forest habitats upon a variety of small mammals, including flying squirrels, woodrats, mice and voles, and a few rabbits. It also eats small birds, bats, and large arthropods. Within the San Bernardino Mountains, the diet of the California spotted owl was summarized as (by frequency of item): Neotoma 39.7 percent, other - primarily invertebrates 38 percent, other mammals 7.3 percent, Peromyscus 7.7 percent, birds 3.5 percent, and Microtus/Clethrionomys 1.7 percent (Gutiérrez, et al. 1995). It usually searches from a perch and swoops or pounces on prey in vegetation or on the ground. It may cache excess food. It forages in late seral stage forests significantly more often than in younger aged stands. Stand attributes include large diameter trees, multiple vegetation strata, and high live-conifer basal area (Gutiérrez, et al. 1995).
Habitat use patterns have been studied for the California spotted owl for the Mt. San Jacinto population (Gutierrez and pritchard 1990). The owls were found primarily in conifer and hardwood stands within conifer forests. A few were observed in live oak forests in deep canyons. The owls were found to not use grasslands, chaparral or open-canopied habitats.
For California spotted owls in the norther Sierra, foraging owls used microhabitats that were characterized by multiple vegetative strata, large tree size classes, high tree basal areas and woody debris. The mean home range for foraging birds within this area has been determined to be 1,439 hectares (Call et al. 1992).
Daily Activity: The California spotted owl exhibits year-long, nocturnal activity (Forsman 1976).
Reproduction: The spotted owl usually nests in a tree or snag cavity or in a broken top of a large tree. It may also nest in a large mistletoe clump, abandoned raptor or raven nest, cave or crevice, on a cliff or on the ground (Zeiner, et al. 1990, Call 1978). Mature, multi-layered forest stands are required for breeding of the spotted owl (Remsen 1978). The nest is usually placed 9-55 meters (30-180 feet) above the ground. The spotted owl breeds from early March through June, with a peak in April and May. It has one brood per year. The clutch size is 1-4 eggs, usually 2. The female incubates and broods the young; the male feeds the female and the young. It may not be sexually mature until 3 years old. The pair may use the same breeding site for 5-10 years, but may not breed every year (Forsman 1976).
The quality of nesting habitat and nest-site selection of a population of the California spotted owl in the San Bernardino Mountains was studied by LaHaye et al. (1997). This study concluded that fledging success was unrelated to nest type, nest tree, nest stand characteristics, or habitat type. Nest productivity was greatest in lower elevation oak/big-cone Douglas-fir habitat and was quantified as 1.7 fledglings per successful nest. Nest stands were characterized by greater variation in tree size, higher canopy closure, and greater basal area of large trees compared with random points. This confirms that the California spotted owls will use a variety of habitats but these habitats are consistently characterized by greater structural complexity compared with available habitat.
Survival: The juvenile survival rate is low and adult survival rate is relatively high for the California spotted owl (LaHaye, et al. 1992). There is empirical evidence from the San Bernardino Mountains that spotted owl reproductive success is significantly higher in lower montane canyon live oak/big-cone Douglas-fir forests than it is in high-elevation montane conifer forests (La Haye et al. 1997). These lower elevation habitats are believed to be productive because of high woodrat densities (the owl's primary prey) in the surrounding chaparral (Stephenson and Calcarone 1999).
Dispersal: California spotted owls are known to migrate altitudinally due to heavy snow pack (Zeiner, et al. 1990). Juveniles disperse from the natal areas in September and October; the species has a strong fidelity to the nest site (Gutiérrez, et al. 1995). Dispersal studies of the California spotted owl population in the San Bernardino Mountains concluded theat juvenile owls dispersed 0.4 to 36.4 kilometers (LaHaye et al. 2001)
Socio-Spatial Behavior: Forsman et al. (1977) found home ranges of the spotted owl in mature Douglas-fir/hemlock forests in Oregon of 120-240 hectares (300-600 acres), with a mean of 180 hectares (450 acres). Gould reported a similar home range size in the Sierra Nevada (Gould 1974). Individual sites are spaced 1.6 to 3.2 kilometers (1-2 miles) apart in suitable habitat (Marshall 1942, Gould 1974). Gould (1977) found that the territory in conifer forests in the Sierra Nevada varied from 40-138 hectares (100-340 acres), with a mean of 93 hectares (230 acres). In the San Bernardino Mountains, home ranges for three California spotted owls were 804 acres, 2,232 acres and 4,611 acres (Gutierrez and LaHaye 1988).
Community Relationships: Great horned owls and goshawks are potential predators of the young spotted owls (Forsman 1976). The spotted owl will actively defend the nest site from common ravens, northern goshawks, and Cooper's hawks. It will attack great horned owls. Researchers may be attacked when attempting to get near the nest (Gutierrez et al. 1995).
The loss of habitat owing to clear felling of forests, and degradation of habitat owing to even-aged tree management are the primary threats to the California spotted owl. Extensive loss of habitat in all three subspecies' ranges has occurred. Secondary losses of habitat include urban and suburban expansion, water development in riparian corridors, agricultural development, fuel wood/oak harvest, reservoir development and mining (Gutiérrez, et al. 1995). The USFS (pers. comm. 1999) identified a major threat to the species as the loss of habitat by wildfire. Much of the forest area has not burned since the advent of fire suppression at the turn of the century.
Cases of shooting or trapping owls have been documented and sometimes the spotted owl is killed by automobiles. The extent of mortality from these causes is unknown but is expected to be low (Gutierrez et al. 1995).
Two populations in southern California have shown declining trends within the last decade. Little is known about the mechanisms limiting and regulating the population size; however nest sites and prey availability may serve as limiting factors (Gutierrez et al. 1995). California spotted owls are believed to function as a metapopulation with separate subpopulations connected by infrequent but persistent interchange of individual owls (Stephenson and Calcarone 1999; Verner et al. 1992; LaHaye et al. 1994).
About one-quarter to one-third of California spotted owls are known to migrate altitudinally due to heavy snow pack in the Sierra Nevada. That is, in the winter, when territories at higher elevations become covered with snow, the owls will move to lower elevations, comprised primarily of hardwoods, in order to hunt (Forsman 1976). The California spotted owl in the San Gabriel Mountains have often been located at the lower elevations at the base of the mountains during annual Christmas bird counts (Verner et al. 1992).
The species requires blocks of 100 to 600 acres of mature forest with permanent water and suitable nesting trees and snags (Forsman 1976). The California spotted owl requires mature forest stands with large trees and snags (Gutiérrez, et al. 1995).
Evidence exists that forests selectively logged in the past can be re-occupied by owls relatively soon (40 to 100 years) if residual forest elements (e.g., snags, coarse woody debris, large trees with cavities) are present (Gutiérrez, et al. 1995).
The California spotted owl on Mt. San Jacinto appears to be well distributed above 1,000 meters in forested habitats (Gutierrez and Pritchard 1990). Densities in the area have been estimated at 0.16 owls per square kilometer. The proportion of subadults in this isolated population is over twice that reported for large contiguous populations of spotted owls which suggests a higher adult mortality. The fecundity on the insular population is either lower than or similar to the northern spotted owl.
For the California spotted owl, a team of scientists and wildlife managers was assembled to conduct a technical assessment of the California subspecies (Standiford et al. 1994; Verner et al. 1992). This team devised an interim conservation plan that specifically recommended protecting all known owl nesting areas, key habitat elements (e.g., large trees), and logging strategies that retained large trees in the Sierra Nevada. The current owl protection plan in southern California includes the protection of all known owl sites on federal forest land.
Barrows, C. W. 1981. Roost selection by spotted owls: an adaptation to heat stress. Condor 83:302-309.
Barrows, C. W., and K. Barrows. 1978. Roost characteristics and behavioral thermoregulation in the spotted owl. Western Birds 9:1-8.
Call, M.W. 1978. Nesting habits and survey techniques for common western raptors. U.S. Dept. Interior Bureau of Land Management. Portland Oregon. Technical Note No 316. 115 pp.
Call, D. R., R. J. Gutierrez, and J. Verner. 1992. Foraging habitat and home-range characteristics of California spotted owls in the Sierra Nevada. Condor 94:880-888.
Dawson, W. R, D. E. S. Brown, J. D. Ligon, J. R. Murphy, J. P. Myers, D. Simberloff, and J. Verner. 1986. Report of the Advisory Panel on the spotted owl. Audubon Conservation Report No. 7. National Audubon Society, New York.
Forsman, E. D. 1976. A preliminary investigation of the spotted owl in Oregon. M.S. Thesis, Oregon State Univ., Corvallis. 127 pp.
Forsman, E. D., E. C. Meslow, and M. J. Strub. 1977. Spotted owl abundance in young versus old-growth forests. Oregon. Wildl. Soc. Bull. 5:43-47.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Gould, G. I., Jr. 1974. The status of the spotted owl in California. Calif. Dep. Fish and Game, Sacramento, Admin. Rep. No. 74-6. 36 pp.
Gould, G. I., Jr. 1977. Distribution of the spotted owl in California. West. Birds 8:131-146.
Gould G. I., Jr. 2002. California Department of Fish and Game. pers. comm.
Gutierrez, R. J., and J. Pritchard. 1990. Distribution, density, and age structure of spotted owls on two southern California habitat islands. Condor 92:491-495.
Gutiérrez, RJ, A.B. Franklin, and W. S. LaHaye. 1995. Spotted owl (Strix occidentalis). In: A. Poole and F. Gill, Eds. The birds of North America. Number 179.
Gutierrez, Rocky J., and W. S. LaHaye. 1988. Ecology of the California spotted owl in the San Bernardino Mountains of California. Progress Report No. 3. Submitted to the San Bernardino National Forest and Snow Summit Ski Corporation. Humboldt State University Foundation.
LaHaye, W. S., R. J. Gutierrez, and D. R. Call. 1992. Demography of an insular population of spotted owls (Strix occidentalis occidentalis). In Wildlife 2001: populations (D. R. McCullough and R. H. Barrett, eds.). Elsevier Applied Science.
LaHaye, W. S., R. J. Gutierrez, and H. R. Akcakaya. 1994. Spotted owl metapopulation dynamics in southern California. Journal of Animal Ecology 63: 775-785.
LaHaye, W. S., R. J. Gutierrez, and D. R. Call. 1997. Nest-site selection and reproductive success of California spotted owls. Wilson Bulletin 109:42-51.
LaHaye, W. S., R. J. Gutierrez, and J. R. Dunk. 2001. Natal dispersal of the spotted owl in southern California: dispersal profile of an insular population. Condor 103: 691-700.
Marshall, J. T., Jr. 1942. Food and habitat of the spotted owl. Condor 44:66-67.
Moen, C. A. 1994. California spotted owl habitat selection in the central Sierra Nevada. Master's thesis, Humboldt State University, Arcata, CA.
Remsen, J. V., Jr. 1978. Bird species of special concern in California. Calif. Dep. Fish and Game, Sacramento. Wildl. Manage. Admin. Rep. No. 78-1. 54pp.
Standiford, R., G. Ahlstrom, L. Blumberg, M. Skinner, C. Rountree, M. Stoker, L. Gallegos, S. Pincetl, B. Snyder, J. White, and R.K. Henly. 1994. Conserving the California spotted owl: Impacts of interim policies and implications for the long-term. Report of the Policy Implementation Planning Team to the Steering Committee for the California Spotted Owl Assessment. Wildland Resources Center, Division of Agriculture and natural Resources, University of California, Davis, California. Report 33.
Stephenson, J. 1991. Spotted owl surveys on the national forests of southern California: a status report and recommendations for the future. USDA Forest Service, San Bernardino National Forest, San Bernardino. CA.
Stephenson, J. R and G. M. Calcarone. 1999. Southern California mountains and foothills assessment: habitat and species conservation issues. General Technical Report GTR-PSW-172. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 402 pp.
United States Forest Service (USFS). 1999. Pers. comm.
Verner, J., K. McKelvey, B. Noon, R. Gutierrez, G. Gould, T. Beck. 1992. The California Spotted Owl: A Technical Assessment of its current status. USDA Forest Service General Technical Report PSW-GTR-133, USDA Forest Service Pacific Southwest Research Station: Albany, California.
Weathers, W. W., P. J. Hodum, and J. Blakesley. 2001. Thermal ecology and ecological energetcis of California spotted owls. Condor 103: 678-690.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
coastal California gnatcatcher (Polioptila californica californica)
State: Species of Special Concern (full species)
Federal: Threatened
The coastal California gnatcatcher is distributed widely within suitable habitat in the Riverside lowlands and San Jacinto Foothills Bioregions especially along the Interstate 15/215 corridor from the Santa Ana River to Temecula and into the Vail Lake area. It is absent from the higher elevations and desert areas. The Coastal California gnatcatcher occurs in 16 Core Areas within the Plan Area including Alessandro Hills, El Cerrito, Lake Mathews-Estelle Mountain Reserve, Alberhill area, the proposed North Peak Conservation Bank/Meadowbrook area, Wasson Canyon, Railroad Canyon, Quail Valley, Sedco Hills, Hogbacks, Murrieta Hot Springs, Lake Skinner, Buck Road to Pourroy Road east of Murrieta Hot Springs, Vail Lake/Wilson Valley including the eastern Temecula Creek area, Rancho California east of Interstate 15 to De Portola Road, and Norco Hills. The coastal California gnatcatcher, as a year-round resident, has lower dispersal capabilities than small passerine birds that are long-distance migrants and thus relies on habitat linkages for localized and regional movements. Because the coastal California gnatcatcher is well known for using coastal sage scrub within the lowland and foothill Bioregions, occurs widely within its suitable habitat, but has specific locations that are Core Areas, it is included as a group 2 species to be managed at a habitat level with site specific requirements in Core Areas and linkages.
The species-specific conservation objectives developed for this species are based upon the best available scientific information existing at the time of MSHCP preparation. Pursuant to the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives may be adjusted as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 77,070 acres of suitable habitat including coastal sage scrub, Riversidean alluvial fan scrub and desert scrub in the Riverside Lowland and San Jacinto Foothills Bioregions.
Include within the MSHCP Conservation Area at least 13 of the Core Areas and interconnecting linkages within 9 Core and Linkage areas including El Cerrito/Lake Mathews-Estelle Mountain Reserve (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres), Alberhill area (Subunit 2 of the Elsinore Area Plan; 3,460 acres), the proposed North Peak Conservation Bank/Meadowbrook area (Subunit 6 of the Elsinore Area Plan; 1,080 acres), Wasson Canyon (Subunit 5 of the Elsinore Area Plan; 2,320 acres), Railroad Canyon/Sedco Hills (Proposed Linkage 8; 5,470 acres), a portion of the Quail Valley area (Proposed Linkage 7; 3,400 acres), Hogbacks/Murrieta Hot Springs (Proposed Core 2 plus Existing Constrained Linkage A; 5,350 acres), Lake Skinner/Buck Road to Pourroy Road east of Murrieta Hot Springs (Existing Core J plus Proposed Extension of Existing Core 5, 6, and 7; 29,060 acres), Vail Lake/Wilson Valley including the eastern Temecula Creek area (Proposed Core 7; 50,000 acres). Due to mapping configuration, some of the coastal California gnatcatcher Core Areas have been combined in order to provide the acreage of MSHCP Conservation Area within the Core Area.
Within the MSHCP Conservation Area, maintain (once every three years) continued use of and successful reproduction at 75 percent of the Core Areas. Successful reproduction is defined as a nest which fledged at least one known young.
The primary habitat for the coastal California gnatcatcher includes coastal sage scrub, desert scrubs, and Riversidean alluvial fan scrub within the Riverside lowlands and San Jacinto foothills Bioregions. Frequently, pockets of coastal sage are located within a matrix of chaparral or grassland areas and these pockets may be occupied. In addition, gnatcatchers occupy other secondary habitats (i.e., chaparral, grasslands, riparian). These secondary habitats may be important as nesting, foraging, and/or dispersal areas, however, only a small proportion of these habitats are occupied and, therefore, only primary habitat is used for the purpose of the conservation analysis (although some unquantified additional conservation value will be provided by the conservation of secondary habitats within the Core Areas and linkages within the MSHCP Conservation Area). The Plan Area supports approximately 140,770 acres of primary habitat for the coastal California gnatcatcher. Table 1 shows the conservation and loss of primary habitat for the coastal California gnatcatcher. A total of 77,070 acres (55 percent) of the primary habitats, coastal sage scrub, desert scrubs, and Riversidean alluvial fan scrub habitats, are conserved within Criteria Area and Public/Quasi-Public Lands.
As part of 1995 PSBS/KTU+A work referenced in the discussion of MSHCP vegetation (MSHCP Chapter 2), PSBS and KTU+A modeled and evaluated variables potentially relevant to the suitability of coastal sage scrub habitat within the Plan Area for the coastal California gnatcatcher. A detailed description of the methodology used to develop the model is presented in their report (PSBS and KTU+A, 1995). The 1995 PSBS/KTU+A work was designed to gather and organize existing information on current and future land uses, identify gaps of information, and evelope tools to evaluate potential alternative reserve designs focused on doastal sage scrub and coastal California gnatcatchers. Variables considered included elevation, slope, patch size, patch shape, proximity to other coastal sage scrub patches, isolation of patches and adjacent land use. The modeling results labeled areas as very high, high, moderate, low and very low with respect to the quality of coastal sage scrub. A total of 104,820 acres of moderate, high, and very high quality coastal sage scrub habitat (PSBS and KTU+A 1995) is present within the Plan Area. These three categories of the habitat quality mapping overlap with the all of the Core Areas of the coastal California gnatcatcher. The high and very high quality coastal sage scrub categories overlap with all of the core population areas except for that in the Hogbacks and Rancho California areas and portions of the Murrieta Hot Springs and Buck Road to Pourroy Road east of Murrieta Hot Springs areas. A total of 64,010 acres (61 percent) of moderate, high and very high quality of coastal sage scrub habitat (based on mapping in PSBS and KTU+A 1995) is conserved within Criteria Area or Public/Quasi-Public Lands. This includes 14,460 acres (80 percent) of the very high quality habitat, 30,700 acres (58 percent) of the high quality habitat, and 16,350 acres (48 percent) of the moderate quality habitat.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
COASTAL CALIFORNIA GNATCATCHER
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Riverside Lowlands and San Jacinto Foothills Bioregions | |||||||
| Desert Scrubs | 2,230 | 2,160 | 0 | 2,160 | 40 | 30 | 70 |
| Riversidean Alluvial Fan Sage Scrub | 5,430 | 2,710 | 1,310 | 4,020 | 160 | 1,250 | 1,410 |
| Coastal Sage Scrub | 133,110 | 43,690 | 27,200 | 70,890 | 19,740 | 42,480 | 62,220 |
| TOTAL | 140,770 | 48,560 (34%) |
28,510 (20%) |
77,070 (55%) |
19,940 (14%) |
43,760 (31%) |
63,700 (45%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described below under Data Characterization, 391 of the 521 point localities within the UCR database have a high location precision. Of these 391 point localities, 234 (60 percent) will be inside the Criteria Area or Public/Quasi-Public Lands. A total of 27 (7 percent) will be in the Rural/Mountainous zone. However, of the 130 (33 percent) points located outside these habitat areas, 37 are mapped in existing residential/urban/exotic areas.
As indicated above, there are definable locations for focusing conservation efforts (i.e., Core Areas for the coastal California gnatcatcher and the linkage areas between the cores). These areas include El Cerrito, Lake Mathews-Estelle Mountain Reserve, Alberhill area, the proposed North Peak Conservation Bank/Meadowbrook area, Wasson Canyon, Railroad Canyon area, a portion of the Quail Valley area, Sedco Hills, Hogbacks, Murrieta Hot Springs, Buck Road to Pourroy Road east of Murrieta Hot Springs, Lake Skinner, and Vail Lake/Wilson Valley including the eastern Temecula Creek area. These Core Areas have been combined in some cases and are reflected by the acreage calculated for each core as follows: El Cerrito/Lake Mathews-Estelle Mountain Reserve (Existing Core C plus Proposed Extension of Existing Core 2; 23,710 acres), Alberhill area (Subunit 2 of the Elsinore Area Plan; 3,460 acres), the proposed North Peak Conservation Bank/Meadowbrook area (Subunit 6 of the Elsinore Area Plan; 1,080 acres), Wasson Canyon (Subunit 5 of the Elsinore Area Plan; 2,320 acres), Railroad Canyon/Sedco Hills (Proposed Linkage 8; 5,470 acres), a portion of the Quail Valley area (Proposed Linkage 7; 3,400 acres), Hogbacks/Murrieta Hot Springs (Proposed Core 2 plus Existing Constrained Linkage A; 5,350 acres), Lake Skinner/Buck Road to Pourroy Road east of Murrieta Hot Springs (Existing Core J plus Proposed Extension of Existing Core 5, 6, and 7; 29,060 acres), Vail Lake/Wilson Valley including the eastern Temecula Creek area (Proposed Core 7; 50,000 acres). The total Core Area acreage conserved within the MSHCP Conservation Area is 123,850 acres. The three core population areas not proposed for conservation (Alessandro Hills, Norco Hills, and Rancho California east of Interstate 15 to De Portola Road) within the MSHCP Conservation Area are generally located within very constrained areas that have already been highly developed. These areas consist of fragmented, small patches of coastal sage scrub habitat. The patches have very high edge effects and some of the point locations have been lost to development.
Several large blocks of habitat supporting the coastal California gnatcatcher will be conserved as Criteria Area and Public/Quasi-Public Lands including the Core Areas at El Cerrito, Lake Mathews-Estelle Mountain Reserve, Alberhill area, the proposed North Peak Conservation Bank/ Meadowbrook area, Wasson Canyon, Railroad Canyon, a portion of the Quail Valley area, Sedco Hills (relatively low number of gnatcatchers but important for the reserve configuration), Hogbacks, Murrieta Hot Springs, Lake Skinner, Buck Road to Pourroy Road east of Murrieta Hot Springs, and Vail Lake/Wilson Valley including the eastern Temecula Creek area. Other locations occupied by the coastal California gnatcatcher but not constituting a Core Area that will be conserved include Sycamore Canyon Regional Park, portions of Temecula west of Interstate 15, and the Badlands.
Areas that are important for preservation for dispersal purposes but that may not contain large numbers of gnatcatchers include several areas that provide essential connections outside of the Plan Area to other populations of the coastal California gnatcatcher. Conservation of areas within the Jurupa Mountains, Pigeon Pass Road area, San Timoteo Creek and the Badlands provide connectivity into San Bernardino County. Conservation of areas in the Cleveland National Forest near the 91 Freeway and Chino Hills area provide connectivity into Orange County. Conservation within the Santa Rosa Plateau Nature Reserve, Santa Margarita Ecological Reserve, and Aguanga area provide connection into San Diego County.
Within the Plan Area there are also large areas conserved that may provide dispersal corridors but that do not contain large number of gnatcatchers. Conservation of the foothills of the Santa Ana Mountains within Cleveland National Forest is provided west of Interstate 15 which provides a broad area for dispersal on the west side of Interstate 15. Conservation of riparian habitat from the Prado Basin along the Santa Ana River provides a linkage that may not be used consistently but that is composed of habitat that the coastal California gnatcatcher has been documented to use occasionally and could use for dispersal.
Conservation of both Core Areas in the form of large blocks of habitat, as described above, as well as narrower linkages for movements between the core population areas is essential for the MSHCP Conservation Area configuration and conservation strategy. Although the gnatcatcher is not as adept at dispersing as some of the long distance migrant bird species, it has been documented to disperse at least 1.1 kilometers (Galvin 1998). Based on observations of coastal California gnatcatchers in a variety of natural and non-natural habitats, it is expected that they may disperse across marginal habitats such as agriculture, disturbed habitats (e.g., fallow fields, abandoned vineyards) and non-native grasslands and are capable of moving across roadways. As much as possible, it is recommended that linkages be as wide as a gnatcatcher territory within the Western Riverside County area, which has been estimated at approximately 400 meters (approximately 1,200 feet), feet based on the diameter of an average territory. Generally, in order to protect against adverse edge effects, it is better for the linkage to be wider than 400 meters (approximately 1,200 feet), however, some areas are currently constrained and for short distances, narrow linkages or stepping stone reserves will be required.
As such, the MSHCP Conservation Area will provide adequate habitat linkages between Core Areas for this species. Linkage widths in the Home Gardens area south to the El Cerrito Core Area are approximately 0.8 to 1.2 kilometers wide. The El Cerrito, Lake Mathews-Estelle Mountain Reserve, and Alberhill Core Areas are contained within a large block of contiguous habitat that at its narrowest is approximately 1.7 kilometers in width. The connection between the Alberhill Core Area and the North Peak Conservation Bank/Meadowbrook area is a narrow (approximately 0.4 kilometers) but relatively short constrained connection of approximately 2 kilometers in length. At that, the linkage is still the minimum width of a territory diameter. The connection between the North Peak conservation Bank Core Area and the Wasson Canyon Core Area also is narrow but also is very short (0.4 kilometer for 0.8 kilometer). The portion of the Quail Valley Core Area that is conserved is well connected to the Wasson Canyon area with the conservation in BLM parcels and Kabian Park. Similar to the North Peak connection to Wasson Canyon, the Wasson Canyon Core Area has a narrow but short linkage to the Railroad Canyon Core Area. This linkage is approximately 0.3 kilometer wide for approximately 0.5 kilometer in length. The Sedco Hills Core Area is a long habitat patch that varies in width from 0.8 kilometer to 1.7 kilometers in width with one pinch point of approximately 0.4 kilometer.
The Sedco Hills Core Area is separated from the Hogbacks area by Interstate 215, however a narrow linkage is provided via a drainage approximately half-way between Scott Road and Clinton Keith Road. This linkage is approximately 0.4 kilometer wide for approximately 0.8 kilometer. The Hogbacks Core Area is a large habitat block that is connected to the Lake Skinner large habitat block and the Buck Road to Pourroy Road large habitat block by narrow linkages that are currently constrained by existing development. These linkages are located within drainages and are provided as more than one linkage to provide for duplicity of connections. These linkages are within the Warm Springs drainage, Tucalota Creek, and Santa Gertrudis Creek. The Lake Skinner Core Area is linked to the Vail Lake/Wilson Valley including the eastern Temecula Creek Core Area by preservation east of Lake Skinner along Tucalota Creek in a 0.8 to 1.25 kilometer linkage. A very large block of habitat is conserved in the Vail Lake/Wilson Valley including the eastern Temecula Creek area which adjoins the San Bernardino National Forest to the east and to the Cleveland National Forest to the south.
Stepping stone reserves conserve some locations of gnatcatchers and connect some of the smaller numbers of Coastal California gnatcatchers which do not comprise core populations including: Sycamore Canyon Regional Park which is connected by Box Springs Mountains to Highgrove by either very narrow drainages or stepping stone reserve and also is connected by stepping stone reserves through the Alessandro Hills and Mockingbird Canyon through wetlands preservation to El Cerrito.
The conservation strategy and MSHCP Conservation Area design for the gnatcatcher takes into account that large scale fires damage gnatcatcher habitat for a relatively long length of time and large areas are necessary to provide refugia for birds and to supply dispersing individuals to a recovered area for re-population. Within the Plan Area, the Alberhill Core Area is separated from other Core Areas by an existing firebreak in the form of the I-15 freeway corridor. Thus, if a wildfire occurs east or west of I-15, the population on the opposite side of the freeway will likely be protected. Duplicate linkages also provide for the temporary loss of function of the coastal sage scrub habitat in the event of a fire (Campbell et al. 1998). A duplicity of habitat linkages composed of sage scrub and other undeveloped habitats which may be composed of native as well as non-native habitats may provide for dispersal ability of the species (Campbell et al. 1998). Several duplicate linkages are preserved within the MSHCP Conservation Area. Between the Hogbacks and Core Areas at Lake Skinner and AD161 area, a network of linkages is designed. Several linkages occur between the Core Areas on the east side of Interstate 15 and the west side to the Cleveland National Forest at Indian Canyon and Horsethief Canyon.
In summary, conservation for this species will be achieved by inclusion of at least 77,070 acres of suitable Conserved Habitat and 13 Core Areas within large blocks of habitat in the MSHCP Conservation Area. In addition, implementation of Objective 3 for this species will document that the MSHCP Conservation Area will maintain (once every three years) the continued use of and successful reproduction at 75 percent of the Core Areas. Successful reproduction is defined as a nest which fledged at least one known young.
The current number of locations of the gnatcatcher in Riverside County is estimated at 250 to 300 pairs. The gnatcatcher is restricted to more lowland areas and is not distributed evenly through the preferred habitat. It occurs in a patchy distribution and thus the suitable habitat as well as the Core Areas and connections of these Core Areas need to be addressed as described in detail above. Numerous small patches and small numbers of gnatcatchers are conserved as well and are likely to be important as providing a source of dispersing birds. These small populations, many of which are documented above to be preserved may be important to prevent further isolation of remaining breeding groups.
About 63,700 acres of potential primary habitat for the coastal California gnatcatcher will be outside the Criteria Area and Public/Quasi-Public designations, or about 45 percent of the total potential primary habitat. Of this, approximately 19,940 acres (14 percent) of potential primary habitat is located within Rural/Mountainous designation areas. Based on the evaluation of habitat quality provided by PSBS and KTU+A (1995), approximately 40,810 acres (39 percent) of moderate, high and very high quality habitat will be outside the MSHCP Conservation Area. This includes 3,470 acres (19 percent) of the very high quality habitat, 20,680 acres (39 percent) of the high quality habitat, and 16,660 acres (49 percent) of the moderate quality habitat.
Core areas not conserved within Criteria Area and Public/Quasi-Public designations include the Norco Hills population (approximately 5 locations), Alessandro Hills (approximately eight locations), a portion of the Quail Valley area (approximately six locations), and Rancho California east of Interstate 15 to De Portola Road (approximately 10 locations some of which may no longer be extant due to recent development in the area). Based on the UCR database, a total of 27 locations (7 percent) will be in the Rural/Mountainous zone and 130 locations (33 percent) are located outside the MSCHP Conservation Area. However, of the 130 points, 37 are mapped in existing residential/ urban/exotic areas.
The location database for the coastal California gnatcatcher contains approximately 521 data points which range in the date of the location point from 1888 to 1999. Approximately 391 data records are of a high degree of precision and will be useful for analysis although many of these point locations could represent duplicate counts for areas that were surveyed in the early 1990s and then surveyed again. The database indicates that there is an adequate amount of information regarding the overall population size and that patterns of occurrences represent areas of use. The habitats represented in these recent and high precision records include coastal sage scrub, chaparral, grassland, alluvial fan scrub, residential or developed, reservoir, agriculture land, and two within riparian or oak woodland habitat. Approximately324 of the recent data records are of a high precision, currently located within Riversidean sage scrub/grassland/chaparral habitats from the vegetation overlay for the Plan Area. Thus, these points are likely to be extant. Approximately 50 of the more recent (1990 or later) and high precision location code data points are overlain with residential/urban/exotic vegetation types and likely no longer exist.
Due to the recent listing and various federal actions regarding the coastal California gnatcatcher and the location within a rapidly developing area of the United States, as well as the controversy that has surrounded the listing of the species, the coastal California gnatcatcher has been well studied by the scientific community and the available literature on the species is very large ( USFWS 1991; USFWS 1993; USFWS 1995; USFWS 1996; USFWS 1999; USFWS 2000) . The literature includes studies on the natural history, habitat requirements, management implications and recommendations. The gnatcatcher has been well studied in western Riverside county mainly due to the establishment of the Southwestern Riverside County Multiple Species Reserve and the accompanying management fund. In addition there is an excellent baseline for the distribution of the gnatcatcher populations within the Plan Area boundary.
The coastal California gnatcatcher (gnatcatcher), a subspecies of the California gnatcatcher, is a small member of the thrush family (Muscicapidae). The gnatcatcher typically occurs in or near sage scrub habitat, which is a broad category of vegetation that includes the following plant communities as classified by Holland (1986): Venturan coastal sage scrub, Diegan coastal sage scrub, maritime succulent scrub, Riversidean sage scrub, Riversidean alluvial fan sage scrub, southern coastal bluff scrub, and coastal sage-chaparral scrub. Coastal sage scrub is composed of relatively low-growing, dry-season deciduous, and succulent plants. Characteristic plants of this community include California sagebrush (Artemisia californica), various species of sage (Salvia sp.), California buckwheat (Eriogonum fasciculatum), lemonadeberry (Rhus integrifolia), California encelia (Encelia californica), and Opuntia spp. Ninety-nine percent of all gnatcatcher locality records occur at or below an elevation of 984 feet (Atwood 1990).
Coastal sage scrub is patchily distributed throughout the range of the gnatcatcher, and the gnatcatcher is not uniformly distributed within the structurally and floristically variable coastal sage scrub community. Rather, the subspecies tends to occur most frequently within the California sagebrush-dominated stands on mesas, gently sloping areas, and along the lower slopes of the coast ranges (Atwood 1990). An analysis of the percent gap in shrub canopy supports the general impression that gnatcatchers prefer relatively open stands of coastal sage scrub (Bontrager 1991). The gnatcatcher occurs in high frequencies and densities in scrub with an open or broken canopy while it is absent from scrub dominated by tall shrubs and occurs in low frequencies and densities in low scrub with a closed canopy (Weaver 1998). The territory size increases as vegetation density decreases and with distance from the coast, probably due to food resource availability. Thus, gnatcatchers will use even sparsely vegetated coastal sage scrub for shelter and to forage for insects as long as perennial shrubs are available (ERCE 1990).
Gnatcatchers also use chaparral, grassland, and riparian or alluvial habitats where they occur adjacent to sage scrub (Bontrager 1991). The use of these habitats appears to be most frequent during late summer, autumn, and winter, with smaller numbers of birds using such areas during the breeding season. These non-sage scrub habitats are used for dispersal, but data on dispersal use are largely anecdotal (Bowler 1995; Campbell et al. 1995). Although existing quantitative data may reveal relatively little about gnatcatcher use of these other habitats, these areas may be critical during certain times of the year for dispersal or as foraging areas during drought conditions (Campbell et al. 1998). Breeding territories have also been documented in non-sage scrub habitat. Campbell et al. (1998) discuss likely hypotheses explaining why non-CSS habitat is used by gnatcatchers including food source availability, dispersal areas for juveniles, temperature extremes, fire avoidance, and lowered predation rate for fledglings.
Environmental, vegetational, and food-abundance characteristics are important aspects of territory quality, however, they are related to the time of year when the evaluation is made (Redak et al. 1997). Based on the studies of Redak et al. (1997) during the breeding season, habitat use was negatively associated with distance to the coast and the elevation of the territory. The habitat use was positively associated with the abundance of adult stages of beetles, flies, spiders and larval stages of all arthropods. Plots with high densities of California sagebrush, flat-topped buckwheat, and white sage were also used by birds. In contrast, during the nonbreeding season, the correlation of habitat use with vegetation and location variables remained but the correlation was no longer present with the arthropod communities.
Historically, gnatcatchers occurred from southern Ventura County southward through Los Angeles, Orange, Riverside, San Bernardino, and San Diego counties, and into Baja California, Mexico, to approximately 30 degrees north latitude near El Rosario (Atwood 1990). A detailed analysis of elevational limits associated with gnatcatcher locality records reveals that a significant portion, 65 to 70 percent of the historic range, may have been located in southern California rather than Baja California (USFWS 2000). The gnatcatcher was considered locally common in the mid-1940's, but by the 1960's this subspecies had declined substantially in the United States owing to widespread destruction of its habitat (Atwood 1990). Currently, the subspecies occurs on coastal slopes of southern California, ranging from southern Ventura southward through Palos Verdes Peninsula in Los Angeles County through Orange, Riverside, San Bernardino and San Diego Counties into Baja California to El Rosario, Mexico, at about 30 degrees north latitude (Atwood 1991). In 1993, the USFWS estimated that approximately 2,562 pairs of gnatcatchers remained in the United States. Of these, 30 pairs occurred in Los Angeles County, 757 pairs occurred in Orange County, 261 pairs occurred in Riverside County, and 1,514 pairs occurred in San Diego County.
The gnatcatcher is found throughout lowland and foothill Bioregions of western Riverside county in coastal sage scrub habitat. The high density areas are found in the western portion of the county along the I-15 corridor continuing east within the southern portion of the Plan Area to Lake Skinner and Vail Lake. The distribution of gnatcatchers in the County does not appear to be uniform along this strip, instead high density patches of several Core Areas exist in generally two locations within the Plan Area, one in the northwestern portion of the Plan Area east of Interstate 15 between Lake Mathews and the City of Lake Elsinore. The other area is in the Murrieta Hot Springs/Lake Skinner area and west to Interstate 215. In 1993, the USFWS estimated the number of pairs of gnatcatchers at 261 (USFWS 1993). Current estimates for gnatcatchers in western Riverside County number around 300 pairs, however the confidence intervals were not reported (USFWS 1996).
From north to south, Core Areas occur at Norco Hills, Alessandro Hills, El Cerrito, Lake Mathews-Estelle Mountain Reserve, Alberhill area, the proposed North Peak Conservation Bank/ Meadowbrook area, Wasson Canyon, Railroad Canyon, Quail Valley, Sedco Hills, Hogbacks, Murrieta Hot Springs, Lake Skinner, Buck Road to Pourroy Road east of Murrieta Hot Springs, Vail Lake/Wilson Valley and eastern Temecula Creek area, and Rancho California east of Interstate 15 to De Portola Road. Other locations with a few gnatcatcher locations but not a key population include Sycamore Canyon Regional Park, Mockingbird Canyon, Temecula west of Interstate 15, and the Badlands.
Genetics: The coastal California gnatcatcher was originally described as a distinct species by Brewster (1881) based on specimens, however, Grinnell (1926) concluded that it is a subspecies of the black-tailed gnatcatcher (Polioptila melanura) which is widely distributed throughout the Sonoran and Chihuahuan deserts of the southwestern United States and Mexico. Atwood (1980, 1988) concluded that the species was specifically distinct from P. melanura, based on differences in ecology and behavior, which was adopted by the American Ornithologists' Union Committee on Classification and Nomenclature (American Ornithologists Union 1957, 1989). Recent mitochondrial DNA sequencing confirmed the species-level recognition of the Coastal California gnatcatcher, which was calculated to differ from the black-tailed gnatcatcher (P. melanura) by 4.0 percent, similar to differences calculated in the black-capped gnatcatcher (P. nigriceps) and white-lored gnatcatcher (P. albiloris) (Zink and Blackwell 1998).
Diet and Foraging: The coastal California gnatcatcher is primarily insectivorous, nonmigratory, and exhibits strong site tenacity (Atwood 1990). The diet deduced from fecal samples resulted in leaf- and plant hoppers and spiders predominating the samples. True bugs, wasps, bees, and ants were only minor components of the diet (Burger et al. 1999). Gnatcatcher adults selected prey to feed their young that was larger than expected given the distribution of arthropod size available in their environment, and chicks were provisioned with larger prey items and significantly more grasshoppers and crickets and spiders. Both adults and young consumed more sessile than active prey items (Burger et al. 1999).
The richness of the insect community within a habitat area may be a useful tool for describing the quality of the habitat (Burger et al. 1996). This is especially important for strictly insectivorous species such as the coastal California gnatcatcher. Gnatcatcher habitat use has been positively associated with total insect species richness and total individual insect abundance (Redak et al. 1996). Thus overall food abundance and diversity plays an important role in territory selection and use for this species (Redak et al. 1996). Habitat use during the non-breeding season showed no clear relationship to any component of the arthropod community (Redak et al. 1997).
Daily Activity: Activity budget data indicate that gnatcatchers are most active and vocal during the morning. A lull in activity usually occurs during mid-day and activity increases again late in the day (Mock et al., 1990).
Reproduction: The breeding season of the gnatcatcher extends from mid February through mid-August, with the peak of nesting activity occurring from mid-March through mid-May. The gnatcatcher nest is a small, cup-shaped basket usually found one to three feet above the ground in a small shrub or cactus. Clutch sizes range between three and five eggs, with the average being four. Juvenile birds associate with their parents for several weeks (sometimes months) after fledging (Atwood 1990). The coastal California gnatcatcher is a year-round resident. Nest building begins during the mid part of March with the earliest recorded egg date approximately March 20 (Mock et al., 1990). Post-breeding dispersal of fledglings occurs between late May and late November. Predation may be a major source of nest failure (Bontrager 1991; Grishaver et al. 1998). In western Riverside County, 78.9 percent of the nesting attempts failed with 52.9 percent suffering from nest predation (Braden 1999).
Nest site attendance by male gnatcatchers was determined to be equal to that of females for the first nest attempt and then decline to almost 1/3 of that of the female for later nesting attempts (Sockman 1998).
The frequency with which various plant species have been recorded as nesting substrata indicates the overall preference of the sage scrub community as the habitat type (Atwood 1980). California sagebrush was chosen 25 percent of the time with other species including white sage, black sage, chamise, cholla, buckthorn, orange, lemonadeberry, and others making up the balance of nest shrub selections (Atwood 1980).
Survival: Gnatcatchers are persistent nest builders and often attempt multiple broods typically upon nesting failure, which is suggestive of a high reproductive potential. This is, however, typically offset by high rates of nest predation and brood parasitism (Atwood 1990). High rates of nest failure may account for the high number of nesting attempts of the coastal California gnatcatcher (Grishaver et al 1998). Gnatcatchers typically live for two to three years, although ages of up to five years have been recorded for some banded birds (Braden et al. 1995). Most of the juvenile birds usually die during the cold winter months, although the percentage was not quantified. Observations indicate that gnatcatchers are highly vulnerable to extreme cold, wet weather (Mock et al., 1990).
Dispersal: Dispersal is a means by which genetic and demographic exchange between subpopulations maintains the viability of the regional metapopulation (Bailey and Mock 1998). Details regarding the dispersal effect on genetic and demographic connectivity of subpopulations and the actual requirements for dispersal are largely unknown (Rotenberry and Scott 1998) but some information can be documented from anecdotal observations. The mean dispersal distance of gnatcatchers banded as nestlings for males was 2.85 km and for females was 3.33 km (Atwood et al. 1996). Mean dispersal of juveniles in Orange County was found to be 1.05 km with one individual dispersing a total of 7.55 km (Galvin 1998). Although the mean dispersal distances that have been documented above are relatively low, dispersal of juveniles is difficult to observe and to document without extensive banding studies. It is likely that the few current studies underestimate the gnatcatcher's typical dispersal capacity because of the difficulty of detecting (Bailey and Mock 1998). Juvenile coastal California gnatcatchers are apparently able to traverse highly man-modified landscapes, including non-native landscaping vegetation, for at least short distances and this underestimation of the species' dispersal capability can lead to an overestimation of the metapopulation's vulnerability to extinction (Bailey and Mock 1998). A few observations of gnatcatcher dispersal behavior indicate that a stepping stone linkage, that is, a serious of small patches of suitable habitat interspersed with developed habitat, is deemed acceptable for situations where the habitat is otherwise fragmented and no contiguous linkage is available (Bailey and Mock, 1998). Additionally, natural and restored coastal sage scrub habitat along highway corridors has been documented to be used for foraging and nesting by gnatcatchers and may serve important dispersal functions (Famolaro and Newman 1998). Typically, however, the dispersal of juveniles requires a corridor of native vegetation which provides foraging and cover opportunities to link larger patches of appropriate sage scrub vegetation (Soule 1991). These dispersal corridors may facilitate the exchange of genetic material and provide a path for recolonization of areas from which the species has been extirpated and increased mating opportunities for unpaired birds (Soule 1991; Galvin 1998).
The natal dispersal, for a non-migratory bird, such as the coastal California gnatcatcher, is an important aspect of the biology of the species (Galvin 1998).
Socio-Spatial Behavior: The coastal California gnatcatcher seems to become highly territorial by late February or early March each year. Males seem to be very vocal during this time period (Mock et al., 1990). In San Diego County the territory size for inland sites was calculated to range between 13 and 39 acres per pair, averaging 24 acres per pair (ERCE 1990). In Riverside County, it was estimated that about 24 acres of sage scrub habitat (3 times the average territory size of 8 acres as measured within the HCP area) was required per pair of coastal California gnatcatchers (Braden 1998, pers. comm.). The distribution of the gnatcatcher is thought to be related to elevation with most of the birds located below 250 m elevation within 35 km of the coast and 500m elevation for inland regions (Atwood and Bolsinger 1992). During the nonbreeding season, gnatcatchers have been observed to wander in adjacent territories and unoccupied habitat increasing their home range size to approximately 78 percent larger than their breeding territory (Preston et al. 1998). Estimates of the territory size should be examined with caution as the calculation may be influenced by differences in data collection and analysis (Atwood et al. 1998).
Coastal California gnatcatchers are most often observed in pairs even in the non-breeding season. They appear to maintain their territories and are relatively sedentary throughout the year (Dunn and Garrett 1987). In fact vocalization rates, which may provide communication within the pair, were highest from August through March (Preston et al. 1998).
Community Relationships: Predation occurs in greater proportion in the upper and lower one third of the nest shrub. Predation was lower in nests with full clutch sizes which may indicate the parents are more attentive to the nest after the clutch is complete (Sockman 1997). Potential predators include scrub jays, greater roadrunners, and cactus wrens which have been observed to be actively mobbed by the gnatcatcher (Bontrager 1991). The coastal California gnatcatcher also is known to be affected by nest parasitism of the brown-headed cowbird. However, the gains in nest success from decreased nest parasitism appear to be negated by increased nest abandonment due to predation before cowbirds have migrated into an area (Braden et al. 1997). Thus, although a cowbird trapping program may reduce parasitism significantly and lower abandonment due to parasitism, nest predation then increases and negates the benefit of the trapping program (Braden et al. 1997). Nest parasitism apparently has resulted in earlier nesting dates of the gnatcatcher which may help compensate for the negative affect of parasitism (Patten and Campbell 1998).
Although the coastal California gnatcatcher may serve as an adequate "umbrella species" for other species that occur in similar habitats and that require a similar territory size or smaller (Fleury et al. 1998), it is not a particularly good indicator of bird-species richness in coastal sage scrub habitat (Chase et al. 1998).
In 1997, the total number of gnatcatchers in the United States was estimated at 2,899 pairs, after subtracting out all gnatcatcher pairs authorized for Take under Habitat Loss Permits, approved natural Community Conservation Plans, Habitat Conservation Plans, and section 7 consultations ("Reinitiation of formal consultation on implementation of the special rule for the coastal Coastal California gnatcatcher [1-6-93-FW-37R1]"). This apparent increase in abundance since 1993 is likely the result of additional surveys occurring within previously unsurveyed areas, as well as increased productivity in response to favorable climatic conditions (USFWS 2000).
Although observed declines in numbers and distribution of the gnatcatcher resulted from numerous factors, habitat destruction, fragmentation and adverse modification are the principal reasons for the gnatcatcher's current threatened status (USFWS 1993). The amount of coastal sage scrub available to gnatcatchers has continued to decrease during the period after the listing of the species. It is estimated that up to 90 percent of coastal sage scrub vegetation has been lost as a result of development and land conversion (Westman 1981a, 1981b; Barbour and Major 1977), and coastal sage scrub is considered to be one of the most depleted habitat types in the United States (Kirkpatrick and Hutchinson 1977; Axelrod 1978; Klopatek et al. 1979, Westman 1987; O'Leary 1990). The fragmentation of habitat may artificially increase populations in adjacent preserved habitat; however, these population surpluses may be lost in subsequent years due to crowding and lack of resources (Scott 1993). In addition, agricultural use, such as grazing and field crops, urbanization, air pollution, increases in fire frequency and the introduction of exotics have all had an adverse impact on extant sage scrub habitat. A consequence of urbanization that is contributing to the loss, degradation, and fragmentation of coastal sage scrub is an increase in wildfires due to anthropogenic ignitions (human caused fires). High fire frequencies and the lag period associated with recovery of the vegetation may significantly reduce the viability of affected subpopulations of the gnatcatcher (USFWS 1991).
Knowledge of the demography of a population is fundamental to determining long-term trends. For birds, the demographic parameters of primary importance are annual breeding success, defined as number of chicks fledged per pair, and recruitment, defined as percentage of fledglings that enter the breeding population. A preliminary demographic model for a population of coastal California gnatcatchers based on observed data was prepared by Woehler et al (1995). Based on the results, for the population to be stable, each breeding pair must replace themselves over their lifetime. The data from a population at U.C. Irvine had a 90 percent mortality (that is, a 10 percent recruitment) and produced 0.64 fledglings per egg. In western Riverside County, 78.9 percent of the nesting attempts failed which translates to an approximately 80 percent mortality (Braden 1999). Thus, for the U.C Irvine example, a pair must produce 30 eggs during their lifetime and must live for five years for the population to remain stable (Woehler et al. 1995).
Gnatcatcher populations appear to be inversely correlated to seasonal total rainfall (Erickson and Miner 1998). Thus increased rainfall during the winter is a mixed blessing in that it is likely that it increases winter mortality but may increase the productivity of the invertebrate prey population base (Erickson and Miner 1998). Other weather-related factors that may influence the distribution of the gnatcatcher include the January mean minimum temperature which, for the coastal California gnatcatcher, has been estimated to be approximately 2.5 degrees C (Mock 1998). This metabolic constraint may preclude gnatcatchers, as a sedentary bird, from occupying otherwise suitable habitat within their range (Mock 1998). This link between a species distribution and physiological adaptations to the climate has been shown previously for other bird species (Hayworth and Weathers 1984).
Gnatcatchers nested earlier, had more successful nests, produced more fledglings, had a longer nesting period, and had lower fledgling costs when their territories were associated with increased grass and forb cover, increased perennial structure, increased horizontal perennial homogeneity, decreased vertical perennial homogeneity, and decreased perennial diversity (Braden et al. 1997). Thus, assessment of habitat quality should take into account these variables for preserve planning.
A habitat-based metapopulation model developed for the coastal California gnatcatcher revealed that the model predicted a fast decline and high risk of population extinction with most combinations of population parameters. The results were most sensitive to density-dependent effects, the probability of weather-related catastrophes, adult survival, and adult fecundity (Akcakaya and Atwood 1997). However, this metapopulation model resulted in the greatest difference on a time horizon of only a few decades. This may be appropriate if the model is used to compare alternative management options but not to make assessments with longer time horizons (Akcakaya and Atwood 1997). Studies providing information on long-scale demography and metapopulation variables are still largely unknown (Rotenberry and Scott 1998).
Structure of the perennial vegetation within coastal sage scrub seems to be an important component leading to successful gnatcatcher reproduction (Braden, 1997). Any disturbance that affects perennial structure and homogeneity within gnatcatcher territories, such as fire or grazing, also may affect gnatcatcher fitness (Braden, 1997). In fact, areas of the Southwestern Multiple Species Reserve that were occupied by gnatcatchers previous to a 1993 fire have not recovered enough to warrant occupation by gnatcatchers to date (Shaughnessy 1999 pers. comm.). In general, recently burned areas are not used by gnatcatchers except on an occasional basis, and five to seven years of recovery may be necessary before gnatcatchers will nest in burned areas (Atwood et al. 1998, Beyers et al. 1994). This slow recovery of CSS in western Riverside county may be due to invasion of exotic annuals after any disturbance. CSS in the County has been reduced by frequent fire, grazing, and invasion of exotic annuals, as well as air pollution (O'Leary and Westman 1988; O'Leary (1990). The frequency of fires in wildland areas tends to increase as fragmentation increases due to urbanization and agricultural activity. Because of the CSS to grass conversion, protection of coastal sage scrub on gabbro basalts may be required to protect this habitat and the gnatcatcher in Riverside County (Minnich and Dezzani 1998).
Fire may be an important factor to consider in MSHCP Conservation Area design for this species and management plans may be necessary to provide a strategic framework for merging the needs for the species with the challenges of fire control (Mackey et al. 1994). Consideration of habitat refugia, burn frequency, and recolonization of recovering burn areas will be necessary for designing reserves for this species (Atwood, et al. 1998). Observations after a major fire of coastal sage scrub reveal that a large proportion of the gnatcatchers within the burned area were displaced to adjacent habitat rather than killed outright and were packed more densely into remaining areas of intact coastal sage scrub (Atwood, et al. 1998). On unburned areas within San Diego and Riverside counties, two pairs per hectare were found, but only 0.02 pair per hectare were found on burned areas (Mayer and Wirtz 1995). However, the gnatcatchers that are able to establish territories on burned areas appear to breed at rates very similar to those on unburned sites (Wirtz and Mayer 1995). The extent and timing of vegetation recovery may determine the habitat suitability for breeding pairs (Wirtz and Mayer 1995).
The presence of gnatcatchers within burned areas may indicate post-fire dispersal or the availability of refugia from the fire (Mayer and Wirtz 1995). Frequent burning of coastal sage scrub may lead to domination of the site by introduced grasses, in addition, burned sage scrub often remains unsuitable for breeding gnatcatchers for more than eight years after burning (ERCE 1991, Zedler et al. 1983, O'Leary 1990). At an inland site, burned 12 years earlier, there was less than 10 percent shrub cover and no gnatcatchers, while annual grasses and mustard species dominated the site (Beyers et al. 1994). Management consideration will need to take into account that large scale fires may damage gnatcatcher populations in both the burned area and the refugia area (Atwood et al. 1998). Due to the issue of periodic fires in occupied habitat and the length of time needed for recovery of CSS, large areas will be necessary to provide refugia for birds and to supply dispersing individuals to a recovered area. As an example within the western Riverside County Plan Area, the Alberhill population is separated from other core populations by an existing firebreak in the form of the I-15 freeway corridor. Thus, if a wildfire occurs east or west of I-15, the population on the opposite side of the freeway will likely be protected. Duplicate linkages also provide for the temporary loss of function of the coastal sage scrub habitat in the event of a fire (Campbell et al. 1998). A duplicity of habitat linkages composed of sage scrub and other undeveloped habitats which may be composed of native as well as non-native habitats may provide for dispersal ability of the species (Campbell et al. 1998).
Other factors that will be relevant for designing a reserve system for the gnatcatcher will be the dispersal distance and average territory size. In western Riverside County, the average dispersal distance for juvenile gnatcatchers has been documented as 1.14 km (Braden et al., 1994a). The distances may be influenced by many factors such as sex, reproductive opportunities, available habitat and other factors. The average territory size for gnatcatchers is 8.42 acres during the breeding season and can expand to 60 acres during the non-breeding season (Braden and Powell, 1994b). Other studies have concluded the territory ranges in size depending on the location and a study in Riverside County concluded the average territory size is 8 acres (ERCE 1990, Braden 1998, pers. comm.). A reserve design for this species will need to maintain connections of breeding habitat such that dispersal between areas can be accomplished and that are large enough to accommodate the largest territory sizes.
Linkages of habitat along linear features such as highways and power-line corridors may be of significant value in linking populations of the gnatcatcher (Famolaro and Newman 1998). Stepping stone linkages which are designed to function as habitat linkages are acceptable but should be line of sight as much as possible (Bailey and Mock 1998). The width of a linkage is recommended to be approximately 1,200 feet. This will provide a linkage wide enough to support a gnatcatcher territory. For linkages less than this width, the gnatcatchers currently mapped for occurring within the linkage may not be able to remain within the area. In the case of narrow habitat widths, the linkage will serve the function of connection of habitat areas only. An important linkage of habitat to maintain or encourage is that from the western Riverside County area north into San Bernardino County (Davis et al. 1998). This linkage is within the Jurupa Hills and connects to the Santa Ana River in Riverside County (Davis et al. 1998). Recently, gnatcatchers have been observed within Jurupa Hills although the area is not surveyed regularly (Davis et al. 1998).
The coastal California gnatcatcher may be suitably analyzed on a landscape or habitat basis rather than on a data point basis due to the fact that it responds well to habitat management and will readily occupy revegetated coastal sage scrub (O'Connell and Erickson 1998, Miner et al. 1998). The fact that gnatcatchers will occupy revegetated coastal sage scrub makes this an important component of long-term management for the species (O'Connell and Erickson 1998). In one study, restored habitat was included in 19 of 22 gnatcatcher territories and nests in restored areas were as likely to produce at least one young as nests in naturally generated scrub (Miner et al. 1998). Additionally, in this study, thirteen percent of the nests were placed within 3 meters of actively used roads or trails and their success rate was similar to that of nests placed further from these high-use areas, thus breeding success of gnatcatchers appears not to be negatively affected by current management practices and levels of public use within park areas. (Miner et al. 1998). Given that this study was conducted within specific State Park areas, additional studies would be helpful for other situations.
The continued fragmentation of habitat over time has increased exposure of gnatcatcher to threats associated with habitat edge (Atwood 1993). Numerous nest predators thrive on habitat edges, and brood parasitism by the brown-headed cowbird (Molothrus ater) appears to be exacerbated by increased edge effects (Bolger et al. 1997, Atwood 1993). Management of edge effects of future development may also be needed although there is little evidence that coastal California gnatcatchers are negatively affected by having their territory located at the edge of urban development (Atwood, 1998). This may be more associated with the use of the gnatcatcher of sage scrub/grassland ecotone. In support of this observation, studies of ‟edge/fragmentation reduced" species versus ‟edge/ fragmentation enhanced" species places the coastal California gnatcatcher in an ‟edge/fragmentation insensitive" category (Bolger et al. 1997). This is a category occupied by the characteristic species of shrub habitats in the region. They tend to be abundant and widely distributed across the landscape and habitat gradients although their abundance is much lower than the other species in the group (Bolger et al. 1997). Other forms of edge management may still be required. Management may include fencing areas occupied by gnatcatchers to protect birds from human and other intruders. Management may include exotic plant removal along edges of development or planting with native shrubs. Analysis of the current shrub cover to shrub cover and composition in 1934 indicates a drastic reduction in native species and increase in non-native grasses and forbs (Minnich and Dezzani 1998). A major portion of the degradation in the Perris plain of Riverside County is within public land with private lands nearby containing higher quality habitat. Attempts to conserve the coastal California gnatcatcher by extending public lands in regions experiencing this habitat degradation may be insufficient (Minnich and Dezzani 1998).
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Wirtz, W. O. II, and A. L. Mayer. 1995. Effects of fire on the breeding of California gnatcatchers, Polioptila californica, in California sage scrub communities. Bulletin of the Ecological society of America 76: 287.
Woehler, E.J., M. Schroeder, T. Stecher, J. Simonsen, and J. Ezovski. 1995. Dynamics of a population of California gnatcatchers, 1991 to 1995. Unpublished abstract.
Zedler, P.H., C.R. Gautier, and G.S. McMaster. 1983. Vegetation change in response to extreme events: the effect of a short interval between fires in California chaparral and coastal sage scrub. Ecology 64: 809-818.
Zink, R. M., and R. C. Blackwell. 1998. Molecular systematics and biogeography of arid land gnatcatchers (Genus Polioptila) and evidence supporting species status of the California gnatcatcher (Polioptila californica). Molecular Phylogenetics and Evolution 9: 26-32.
Cooper's hawk (Accipiter cooperii)
State: Species of Special Concern
Federal: Partners in Flight Priority Bird Species; San Bernardino National Forest Sensitive
Other: Audubon Society Blue List
The Cooper's hawk is widely distributed throughout the MSHCP Plan Area within suitable habitat. It occurs within all Bioregions of the Plan Area. There are several areas that appear to be Core Areas including the Prado Basin/Santa Ana River, San Timoteo Canyon, Temescal Wash, Wasson Canyon, Slater Canyon, Santa Rosa Plateau West, Temecula Creek, Murrieta Creek, Tucalota Creek, Vail Lake, Wilson Valley, San Bernardino National Forest, and Cleveland National Forest. Because it is well known for using riparian scrub, forest and woodland, oak woodland and forest, and montane coniferous forest, occurs in all Bioregions of the Plan Area, but has specific locations that are Core Areas, it is a Group 2 species.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 54,580 acres of suitable habitat including riparian scrub, forest, and woodland, oak woodland and forest, and montane coniferous forest.
Include within the MSHCP Conservation Area at least 10 Core Areas at (1) the Prado Basin/Santa Ana River (9,670 acres), (2) San Timoteo Canyon (Subunit 3 of The Pass Area Plan; 2,290 acres), (3) Temescal Wash (Subunit 3 of Temescal Canyon Area Plan; 4,010 acres), (4) Wasson Canyon (Subunit 5 of Elsinore Area Plan; 2,320 acres), (5) Temecula Creek (Subunit 2 of Southwest Area Plan; 850 acres), (6) Murrieta Creek (Subunit 1 of Southwest Area Plan; 2,060 acres), (7) Vail Lake (Subunit 3 of Southwest Area Plan; 12,320 acres), (8) Wilson Valley (Subunit 2 of REMAP Area Plan; 33,540), (9) San Bernardino National Forest (Existing Core K;149,750 acres), (10) Cleveland National Forest (Existing Core B; 71,490 acres).
For the purpose of the conservation analysis, potential habitat for the Cooper's hawk includes riparian scrub, woodland, and forest habitat, oak woodland and forest, and montane coniferous forest within all Bioregions of the Plan Area. Based on these habitats, the Plan Area supports approximately 76,680 acres of potential habitat for the Cooper's hawk. Table 1 shows the conservation and loss of potential habitat for the Cooper's hawk. Overall, approximately 54,580 acres (71 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public Lands.
This species occurs within the Forest Service lands as well as the lowland Bioregions as a breeding and foraging species. It occurs predominantly within riparian scrub, woodland and forest, oak woodland and forest, and montane coniferous forest. Under the existing Forest Land allocation plan, these locations and habitats are generally located within the San Jacinto Wilderness and San Mateo Canyon Wilderness areas and in most of the grazing allotments as well. The Cooper's hawk has been documented to occur in the area of Fulmor Lake and Pine Cove and along the foothills areas and within the western portion of the Cleveland National Forest. Conservation of riparian and woodland habitats and Core Areas within the San Bernardino National Forest and Cleveland National Forest are important conservation methods for this species.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
COOPER'S HAWK
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| All Bioregions | |||||||
| Riparian Scrub, Woodland, Forest | 14,610 | 3,920 | 7,270 | 11,190 | 370 | 3,050 | 3,420 |
| Woodlands and Forests (oak) | 32,180 | 2,390 | 20,500 | 22,890 | 5,020 | 4,270 | 9,290 |
| Montane Coniferous Forest | 29,890 | 20 | 20,480 | 20,500 | 40 | 9,350 | 9,390 |
| TOTAL | 76,680 | 6,330 (8%) |
48,250 (63%) |
54,580 (71%) |
5,430 (7%) |
16,670 (22%) |
22,100 (29%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
As described below under Data Characterization, 85 of the 178 relatively recent point localities have a precision of "1." Of these 85 point localities, 16 (19 percent) will be inside the Criteria Area and 14 (17 percent) are located within Public/Quasi-Public Lands. A total of 12 (14 percent) will be in the Rural/Mountainous lands. Of the 43 high precision recent points located outside the MSHCP Conservation Area, 21 points are located in residential/urban/exotic or agriculture areas and may have been observed in flight. One of these 43 locations outside the MSHCP Conservation Area was observed within suitable habitat composed of riparian habitat and the balance are located outside suitable habitat areas within non-native grassland, chaparral, or Riversidean sage scrub. Conservation of this species will be considered from a landscape perspective due to the fact that the suitable habitat has been well defined. Providing additional suitable habitat that is not currently occupied may assist with the recovery of the species.
In addition, there are definable locations composed of Core Areas for focusing conservation efforts which are included within the MSHCP Conservation Area. These conserved Core Areas include the Prado Basin/Santa Ana River (9,670 acres), San Timoteo Canyon (Subunit 3 of The Pass Area Plan; 2,290 acres), Temescal Wash (Subunit 3 of Temescal Canyon Area Plan; 4,010 acres), Wasson Canyon (Subunit 5 of Elsinore Area Plan; 2,320 acres), Temecula Creek (Subunit 2 of Southwest Area Plan; 850 acres), Murrieta Creek (Subunit 1 of Southwest Area Plan; 2,060 acres), Vail Lake (Subunit 3 of Southwest Area Plan; 12,320 acres), Wilson Valley (Subunit 2 of REMAP Area Plan; 33,540). The Core Areas within the San Bernardino National Forest (Existing Core K;149,750 acres) and Cleveland National Forest (Existing Core B; 71,490 acres) are conserved as described above. A total of 288,300 acres of Core Areas as estimated by the subunit acreages (core acreage for the forest service lands) are conserved within the MSHCP Conservation Area. Constrained areas of Tucalota Creek and a portion of Santa Rosa Plateau West are conserved.
As depicted on the MSHCP Plan Map (Figure 3-1, MSHCP Volume I), certain areas adjacent to or in proximity to the MSHCP Conservation Area are designated as Rural/Mountainous in the County's General Plan. These areas are generally constrained for development due to steep topography and the level of development in these areas is anticipated to be of a low density, rural residential character. While these areas will not be included within the MSHCP Conservation Area or managed for the benefit of species conserved under the MSHCP, the low levels of development anticipated in these areas will provide an edge to the MSHCP Conservation Area that may be of value to certain species. For the Cooper's hawk, conservation of the Santa Rosa Plateau along the Tenaja Corridor and Slater Canyon just west of Lake Elsinore are important as a core population areas. MSHCP Conservation Area locations in these areas are generally surrounded by Rural/Mountainous designations. Potential development in these areas is anticipated to retain vacant areas, and wetlands in particular due to the Riparian/Riverine Areas and Vernal Pools policy, which will provide nesting and foraging habitat for the Cooper's hawk. A total of 5,430 acres (7 percent) of potential habitat will be designated Rural/Mountainous.
Several large blocks of habitat supporting or potentially supporting the Cooper's hawk will be conserved as Criteria Area and Public/Quasi-Public designations, including the Prado Basin/Santa Ana River, Sycamore Canyon Regional Park, Lake Mathews-Estelle Mountain, Wasson Canyon, Sedco Hills, foothills of the Santa Ana Mountains, Cleveland National Forest, a portion of the Santa Rosa Plateau, Lake Skinner-Diamond Valley Lake, San Jacinto Wildlife Area-Lake Perris, the Badlands, Vail Lake, Wilson Valley, San Jacinto River, Lake Elsinore, Badlands and Potrero Valley. Some of these areas include Core Areas. Other drainages that are provided protection by the designation as MSHCP Conservation Area, including areas occupied by Cooper's hawk or containing Core Areas of the Cooper's hawk, include Temescal Wash, San Timoteo Creek, Temecula Creek, Tucalota Creek, Bautista Creek, and Murrieta Creek. Protection is also provided within Cleveland National Forest and San Bernardino National Forest areas as discussed above. Some of the large blocks of habitat have not been mapped as containing Cooper's hawks or drainages with riparian or woodland habitat. However, these habitat blocks may have smaller riparian systems that contain potentially suitable habitat and could be occupied by Cooper's hawks in the future. As a long-distance migrant and a species with a large foraging area, Cooper's hawks are likely able to discover and use patches of riparian or woodland habitat that have not been documented to be used in the past. As documented below, the Cooper's hawk is willing to nest within relatively close contact to humans and may even occur within suburban areas as a nesting bird.
Additionally, the MSHCP Conservation Area will provide adequate habitat linkages or stepping stones between Core Areas for this species and will include smaller drainages that may support small numbers of the species. The Prado Basin Core Area is linked along the Santa Ana River to San Bernardino and Orange counties. This riparian area is linked to the south by the Temescal Wash to Lake Mathews and Lake Elsinore. Riparian habitat within the Vail Lake area is linked to the Lake Skinner-Diamond Valley Lake area via Rawson Canyon. Tucalota Creek provides a linkage from Lake Skinner to Murrieta Creek. The Vail Lake area is also linked to the Santa Rosa Plateau and then to the Santa Margarita River by the riparian habitat in Temecula Creek and Murrieta Creek. The Badlands area provides a major habitat block that provides a linkage to Potrero Creek, Lake Perris and Mystic Lake/San Jacinto Wildlife Area, and to San Timoteo Creek.
In summary, conservation for this species will be achieved by inclusion of at least 54,580 acres of suitable Conserved Habitat and 10 Core Areas including the Prado Basin/Santa Ana River, San Timoteo Canyon, Temescal Wash, Wasson Canyon, Temecula Creek, Murrieta Creek, Vail Lake, Wilson Valley, San Bernardino National Forest, and Cleveland National Forest.
About 22,100 acres (29 percent) of potential habitat for the Cooper's hawk will be outside the Criteria Area and Public/Quasi-Public designations and individuals within these areas will be subject to Incidental Take consistent with the Plan. Of this, approximately 5,430 acres (7 percent) of potential habitat are located within Rural/Mountainous designation areas. While the Rural/ Mountainous areas are not included within the MSHCP Conservation Area and will not be managed for the benefit of wildlife, the anticipated levels of development in these areas will likely be consistent with maintaining some habitat for the Cooper's hawk. A portion of the core population within the Santa Rosa Plateau is within the Rural/Mountainous designation and is not considered to be conserved. The population at Slater Canyon is also within the Rural/Mountainous designation and is not considered to be conserved. The core population area at Tucalota Creek is constrained by existing development and although habitat is provided within the drainage by conserved riparian scrub, woodland and forest, the individuals within this drainage are not considered to be conserved.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The location database for the Cooper's hawk includes approximately 230 data records from 1888 to 2000. Of these records, approximately 178 are relatively recent (within the past 10 years) and of these, 85 are of high precision and may be accurately located within the Plan Area. Approximately 21 of these high precision records are located within developed areas and although they may no longer exist, they may represent a wintering or transient bird hunting within a residential neighborhood. The rest occur within non-native grassland, sage scrub, chaparral, riparian and oak woodlands, montane coniferous, open water/reservoirs, crop lands and other vegetation communities that are likely occupied by the species for foraging or nesting. The database does not identify those records that are breeding locations.
A moderate amount of literature is available for the Cooper's hawk because it is a bird of prey and is of interest from a community perspective in relation to potential competition with congeners. Most of the literature pertains to general natural history, niche determination, and the accipiters in general. Few controlled scientific studies have been conducted. However, some management studies are available. Very little information is available for the Plan Area other than what is available regarding basic distribution information.
Throughout its range, the Cooper's hawk breeds in deciduous, mixed, and evergreen forests and deciduous stands of riparian habitat (Rosenfield and Bielefeldt 1993). The Cooper's hawk breeds primarily in riparian areas and oak woodlands and apparently is most common in montane canyons (Garrett and Dunn 1981; Hamilton and Willick 1996). It frequents landscapes where wooded areas occur in patches and groves and it often uses patchy woodlands and edges with snags for perching (Beebe 1974). This species is seldom found in areas without dense tree stands or patchy woodland habitat (Zeiner, et al. 1990). Within the range in California, it most frequently uses dense stands of live oak, riparian deciduous, or other forest habitats near water (Zeiner, et al. 1990). Dense stands with moderate crown-depths are usually used for nesting (Zeiner, et al. 1990). The Cooper's hawk tends to nest in stands with lower densities of taller and larger trees and a greater proportion of hardwood cover than conifer species when compared to other accipiters (Trexel, et al. 1999). Migrant and wintering birds are generally more catholic in their choice of habitats and may be found with regularity in developed (e.g., suburban) areas. They hunt in broken woodland and habitat edges, catching predominantly avian prey in the air, on the ground, and in vegetation.
The Cooper's hawk apparently reduces the niche overlap with the northern goshawk by using areas with greater shrub cover, flatter terrain, and locations that are closer to roads, forest openings, and human habitation (Bosakowski, et al. 1992).
The Cooper's hawk is tolerant of human disturbance and habitat fragmentation and breeds in suburban and urban settings (Murphy, et al. 1988). The urban sites have included isolated trees in residential neighborhoods with commercial and recreational activities less than 150 meters distant and houses 20 to 30 meters distant. Typically, there is some forest edge habitat included within their home range even if nesting within an urban setting and this forest edge may serve as the primary hunting site (Rosenfield and Bielefeldt 1993).
Cooper's hawks breed from British Columbia eastward to Nova Scotia and southward to northern Mexico and Florida (AOU 1998). Specifically, it nests from southern British Columbia, northwestern Montana, Wyoming, eastern North Dakota, southern Manitoba, western Ontario, northern Michigan, southern Ontario, Southern Quebec, Maine, and Nova Scotia, south to Baja California, south-central Texas, Louisiana, central Mississippi, central Alabama, and central Florida (Terres 1980; Reynolds 1975).
The species winters from British Columbia eastward to New England and southward primarily to Honduras (AOU 1998). The wintering range includes the area from Washington, Colorado, Nebraska, Iowa, southern Wisconsin, southern Minnesota, southern Michigan, southern Ontario, New York, southern Maine and Massachusetts south through the rest of the United States to Costa Rica (Terres 1980). The Cooper's hawk makes up a large part of the great fall flights of hawks that pass over the United States in September, they fly high and seem to prefer to fly when the wind is from the northwest (Bent 1937).
In California, the Cooper's hawk is a breeding resident throughout most of the wooded portion of the state. It breeds in the southern Sierra Nevada foothills, New York Mountains, Owens Valley, and other local areas in southern California. Its breeding range is from sea level to above 2,700 m (0-9000 ft). This species was once considered a common nester throughout California (Grinnell and Miller 1944). In southern California, the species is present year-round nearly throughout the state, except for the Colorado River and desert areas, where the species no longer breeds (Garrett and Dunn 1981). Although the Cooper's hawk breeds in southern California and has a year-round resident population, it also occurs in the region as a spring and fall migrant and as a winter resident (Garrett and Dunn 1981).
There is little available data on changes in the distribution of the Cooper's hawk. The species appears to be increasing in North Dakota and Minnesota (Rosenfield and Bielefeldt 1993).
Cooper's hawks apparently may be found nearly throughout the Plan Area in appropriate woodland habitats (Patten, 1998, pers. comm.). Data records are located throughout much of the Plan Area except in the easternmost desert areas and some of the montane areas. The lack of data points within these areas may be due to low survey effort. Cooper's hawks have been documented that they may be found in all of the mountainous areas but they occur at low densities (Stephenson and Calcarone 1999). Many of these records may be for spring and fall migrating transients or a wintering population.
Locations of the Cooper's hawk appear to be concentrated along the Prado Basin/Santa Ana River, San Timoteo Canyon, Temescal Wash, Wasson Canyon, Slater Canyon, Santa Rosa Plateau West, Temecula Creek, Murrieta Creek, Tucalota Creek, Vail Lake, Wilson Valley, San Bernardino National Forest, and Cleveland National Forest. Important breeding populations include a large concentration in the Prado Basin and contiguous reaches of the Santa Ana River. Cooper's hawks also occur in woodland habitats (at least in winter) throughout the Plan Area. They have been recorded within shrubby habitats as well, probably as a foraging observation due to the lack of trees for nesting. Although surveys in the Prado Basin and contiguous reaches of the Santa Ana River have been adequate in recent years, surveys of similar intensity have not been conducted in other woodland areas throughout the large majority of the Plan Area.
Other geographic locations recorded within the U.C. Riverside database include: Box Springs Mountains, Mockingbird Canyon, El Cerrito, Lake Mathews-Estelle Mountain, Gavilan Hills, Motte-Rimrock Reserve, March ARB, Lake Perris, Mystic Lake/San Jacinto Wildlife Area, Quail Valley, Wildomar, Santa Rosa Plateau East, Sage, Lake Skinner, Badlands, Beaumont, Bautista Creek, Potrero Creek, and foothills of the Santa Ana Mountains.
Genetics: A presumed natural hybrid of the Cooper's hawk and northern goshawk was reported by Gray in 1958 (Terres 1980). A. cooperii, A. gundlachi, and A. bicolor comprise a super species apparently evolved from a common stock of tropical American accipiters (Brown and Amadon 1968).
Diet and Foraging: For the Cooper's hawk, avian prey items, especially passerines, comprise 70 percent of the number of food items and 58 percent of the dietary biomass delivered to Cooper's hawk broods at two nests surrounded by a mixed grass prairie with mammalian prey making up the remainder (Peterson and Murphy 1992). In general, during breeding and non-breeding, the Cooper's hawk uses avian prey predominantly, sometimes taking fish and mammals (Terres 1980). In comparison to the northern goshawk, the Cooper's hawk takes more avian prey (Bosakowski, et al. 1992b; Whaley and White, 1994). The Cooper's hawk catches small birds, especially young birds during the nesting season, and small mammals; it also takes reptiles and amphibians.
The Cooper's hawk hunts in broken woodland and habitat edges; it catches prey in the air, on the ground, and in vegetation. Sometimes it runs prey down in dense thickets. It uses cover to hide, attack, and approach prey; it also soars and makes low, gliding search flights (Zeiner, et al. 1990). It forages by dashing through the woods in a low, swift flight, around trees, through the brush and reaches out in the air or on the ground to catch avian prey with the talons (Terres 1980). After catching its prey, the Cooper's hawk may fly with the prey to a water source in order to drown it (Terres 1980).
Daily Activity: The Cooper's hawk is a year-long, diurnally active bird (Zeiner, et al. 1990).
Reproduction: The Cooper's hawk breeds primarily in riparian areas and oak woodlands and apparently is most common in montane canyons (Garrett and Dunn 1981; Hamilton and Willick 1996). It usually nests in second-growth conifer stands, or in deciduous riparian areas, usually near streams or open water (Zeiner, et al. 1990). Throughout much of the west, the Cooper's hawk nests in stands of cottonwoods along stream courses especially where the tree stands are fairly large (Call 1978). Denser stands of trees with moderate crown-depth are used for nesting. It appears that the vertical structure of the nest site tree is more important to the nest-site selection than the horizontal structure (Wiggers and Kritz 1991).
A study comparing nesting habits of Cooper's hawk and sharp-shinned hawk, found that Cooper's hawks tend to nest in stands with lower densities of taller and larger trees with a greater proportion of hardwood cover (Trexel, et al. 1999). It apparently does not tolerate nesting sharp-shinned hawks in the vicinity of its nest (Terres 1980).
In urban settings in Tucson, Arizona, Cooper's hawks have been found nesting mainly in eucalyptus (70.8 percent), aleppo pine (25.0 percent) and cottonwood trees (4.2 percent) (Boal, et al. 1998). Nest trees were found to be taller and of greater diameter than randomly sampled trees and thus had more canopy cover and the nest trees were often the largest tree in the nest site. Although nest sites were always in heavily forested areas, they were significantly closer to forest openings and wetland, were usually on level ground and were never located on a ridgeline or steep upper slope (Bosakowski, et al. 1992a).
The Cooper's hawk locates its nest on a horizontal limb of a pine or hardwood, near the trunk or in the crotch of a hardwood tree species, usually 10 to 60 feet above the ground and sometimes uses an old nest of a crow (Harrison 1978). It also often nests just below the lowest live limbs (Zeiner, et al. 1990). The nest is typically a platform of sticks and twigs lined with bark (Call 1978).
Cooper's hawk eggs are laid in February through June and the clutch size is 3 to 6 eggs; usually 4 to 5 eggs (Brown and Amadon 1968). Eggs are incubated mostly by the female for approximately 24 days (Terres 1980). Incubation is usually started after laying the third egg, thus hatching is asynchronous for the fourth and later eggs. The young birds usually depart the nest at 30 to 34 days but continue to be brought food for up to 7 weeks after leaving the nest.. The young may remain together near the nest for another 5 to 6 weeks (Rosenfield and Bielefeldt 1993). In rural Wisconsin, Rosenfield, et al. (1995) found a minimum intergeneration turnover time of six years for breeding Cooper's hawks.
Survival: One banded individual of the Cooper's hawk was recorded as being shot at 7 years 5 months old (Terres 1980). The maximum reported age is 12 years (Rosenfield and Bielefeldt 1993). The yearly fledging success is about 2 young/ pair with nesting success of 57 percent to 93 percent (Craighead and Craighead 1956; Rosenfield and Bielefeldt 1993). Mortality rates have been estimated as 72 percent to 78 percent in the first year, 34 percent to 37 percent thereafter (Rosenfield and Bielefeldt 1993).
Dispersal: Although it is mostly a year-long resident, some Cooper's hawks from more northern areas, migrate into California. The Cooper's hawk may also move downslope and south from areas of heavy snow and return to the general nesting area in the spring (Zeiner, et al. 1990). The mean distance from the natal site to the breeding site is 12 kilometers for males and 14.4 kilometers for females. Adult birds frequently reoccupy nesting areas and breeding site fidelity is assumed (Rosenfield and Bielefeldt 1993). The Cooper's hawk may reuse the same nest site for multiple years (Call 1978).
Socio-Spatial Behavior: Nest sites of the Cooper's hawk within stands of oaks are located approximately 2.7 kilometers (1.6 miles) apart and thus are distributed widely but sparsely within woodland habitat (Zeiner, et al. 1990). The seasonal home range size has been estimated at 784 hectares with the daily home range averaging 231 hectares (Murphy, et al. 1988). Cooper's hawks may require a minimum of 6 hectares (15 acres) of suitable, undisturbed timber for nesting (Call 1978). Rosenfield, et al. (1995) found a nesting density of 331 hectares/pair in a long-term study in rural Wisconsin. Studies of urban areas have reported a maximum density of 272 hectares/pair, according to this same study.
In Michigan, Craighead and Craighead (1956) measured four home ranges of Cooper's hawks that averaged 311 hectares (768 acres) and varied from 96-401 hectares (237-992 acres); they estimated that 17 other home ranges averaged 207 hectares (512 acres), and varied from 18-531 hectares (45-1312 acres). They reported one home range in Wyoming of 205 hectares (506 acres). Males defend an area about 100 meters (330 feet) around potential nest sites prior to pair formation (Brown and Amadon 1968). Nests in Oregon were 3.2 to 4.2 kilometers (2 to 2.6 miiles) apart (Jackman and Scott 1975). Elsewhere, nests have been reported 1.6 to 2.4 kilometers (1 to 1.5 miles) apart (Meng 1951, Brown and Amadon 1968). Of 77 territories in California, in oak stands, mean distance between nests was 2.6 kilometers (1.6 miles) (Zeiner, et al. 1990).
Community Relationships: The Cooper's hawk is an important predator of small birds. Nestlings and immatures not yet skilled at catching prey may be killed by ravens, northern goshawks, and great horned owls (Beebe 1974). The species may compete, to a limited extent, with sharp-shinned hawks and northern goshawks (Beebe 1974).
Although the northern goshawk is a potential competitor, niche overlap is reduced by using different habitats and by using different species of prey, different sizes of prey and by foraging in different zones (Bosakowski, et al. 1992b). The Cooper's hawk is determined to be more of a generalist from this study by having the greatest niche width. The study suggests that past and current competition may have been responsible for segregating the niches of the Cooper's hawk and northern goshawk. When compared to the sharp-shinned hawk, another potential competitor, the Cooper's hawk used mostly deformed nest trees and tended to place nests below the tree canopy (Wiggers and Kritz 1991).
Recently there have been declines in the population of the Cooper's hawk in California (Remsen 1978). Previously judged to be relatively common to even abundant, for a raptor, in autumn in suitable habitat, southern California's breeding population of the Cooper's hawk reportedly has been reduced in recent decades, especially in lowland areas where much riparian woodland has been destroyed (Grinnell and Miller 1994; Garrett and Dunn 1981). Only approximately 40 pairs were detected in nearby Orange County during recent breeding bird atlas survey efforts there (Gallagher 1996). Habitat destruction, mainly in lowland riparian areas, due to urbanization and development is probably the main threat, although direct or indirect human disturbance at nest sites can be equally detrimental (Remsen 1978; Boal and Mannan, 1998).
Timber harvests may alter the suitability of nesting or foraging habitats as well as the prey populations on a local or regional scale but the magnitude and seasonality of such impacts are uncertain. Breeding and nest site habitats are diverse and apparently not limiting in some areas (Rosenfield and Bielefeldt 1993).
Other threats to the species include illegal Take of nestlings and to a less extent, the effects of pesticides (U.S.F.S. pers. comm. 1999). A serious decline occurred in the 1970s during the nesting season probably due to eggshell thinning resulting from pesticides (Terres 1980; Henny and Wight 1972).
Cooper's hawks occur in landscapes where wooded areas occur in patches and in groves, often using patchy woodlands and edges with snags (Beebe 1974). Many of the commonly used forest stand structural measurements, such as basal area and tree density, may not be adequate for predicting suitable accipiter nesting habitat (Siders and Kennedy 1996). Nesting and foraging usually occur near open water or within or near riparian vegetation (Zeiner, et al. 1990). It has been hypothesized that four factors affect the use of a stand of trees by nesting Cooper's hawks: stand type, stand density, stand age, and degree of fragmentation (Ehrlich and Drickamer 1993).
The Cooper's hawk population within the Prado Basin and surrounding Santa Ana River drainage apparently has increased within the Prado Basin during the course of 14 years of habitat and species conservation efforts and monitoring at that locale (L. R. Hays, USFWS, pers. obs.). Although fairly large when monitoring began in 1983, the Prado Basin/Santa Ana River Cooper's hawk population is even larger today.
Boal, et al. (1999) compared breeding ecology in urban and "exurban (i.e., undeveloped, natural)" areas in southeastern Arizona. His group found urban pairs to nest earlier, have a much higher nestling mortality (50.3 percent in urban settings compared with 4.9 percent in exurban areas), and a higher overall nest failure rate. The studied found urban nestlings to primarily die from trichomoniasis and that free-ranging Cooper's hawks in urban areas primarily die from collisions, most often with windows. In a separate study, Boal's team (1998) found urban nest trees in Tucson, Arizona to be in high-density residential area (65.9 percent) and high-use recreational areas (22.7 percent).
The type of response and intensity of the Cooper's hawk aggressive response to human intrusion near a nest site varies among individuals and probably also varies with the stage of nesting. Many breeding birds respond by remaining inconspicuous, neither vocalizing nor behaving aggressively in the presence of humans. Some individuals may leave the immediate vicinity of the nest, however, the human distance at which this behavior occurs has not been reported (Rosenfield et al. 1985). The implication of human intrusion into the nesting area of the Cooper's hawk is that the nesting attempt may fail, however these implications have not been reported to seriously impact the nesting success of the Cooper's hawk (Rosenfield et al. 1985).
In northern New Jersey, where, in 1993, only 18 nesting Cooper's hawks were known in the area, researchers recommended that any nest site occurring in a wilderness area be protected from habitat alterations within a 0.6 kilometer radius around the nest site (Bosakowski, et al. 1993).
Livestock exclosures, reforestation, and other measures have been suggested for riparian nesting habitat in some regions however there is no documentation of the relative effect of such measures. Timing timber harvests for the nonbreeding season or for stands that are unused by the Cooper's hawk may avoid impacts to known nests. Stands that have been thinned but not clear cut, if done during the nonbreeding season are then reoccupied the next season for breeding (Rosenfield and Bielefeldt 1993).
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Beebe, F.L. 1974. Field studies of the Falconiformes of British Columbia. Brit. Col. Prov. Mus. Occas. Paper No. 17. 163 pp.
Bent, A. C. 1937. Life histories of North American birds of prey. Part 1, U. S. National Museum Bulletin. 170. 482pp.
Boal, C. W. and R. W. Mannan. 1998. Nest-site selection by Cooper's hawks in an urban environment. J. Wildl. Management 62: 864-871.
Boal, C. W. and R. W. Mannan. 1999. Comparative breeding ecology of Cooper's hawks in urban and exurban areas of southeastern Arizona. Journal of Wildlife Management : 63:77-84.
Bosakowski, T., R. Seiser, D. G. Smith and L.J. Niles. 1993. Loss of Cooper's Hawk nesting habitat to suburban development: Inadequate protection for a state-endangered species. Journal of Raptor Research.27: 26-30.
Bosakowski, T., D. G. Smith, and R. Speiser. 1992a. Nest sites and habitat selected by Cooper's hawks, Accipiter cooperii,à`Eánorthern New Jersey and southeastern New York. Canadian Field-Naturalist 106: 474-479.
Bosakowski, T., D. G. Smith, and R. Speiser. 1992b. Niche overlap of two sympatric-nesting hawks, Accipiter spp., in the New Jersey-New York highlands. Ecography 15: 358-372.
Brown, L., and D. Amadon. 1968. Eagles, hawks and falcons of the world. 2 Vols. Country Life Books, London. 945pp.
Call, M. W. 1978. Nesting Habitats and surveying techniques for common western raptors. Technical Note TN-316. U.S. Department of the Interior - Bureau of Land Management, Denver Service Center.
Craighead, J. J., and F. C. Craighead, Jr. 1956. Hawks, owls and wildlife. Stackpole Books, Harrisburg, PA. 443pp.
Ehrlich, R. M., and L. C. Drickamer. 1993. Habitats used for nesting by Cooper's hawks Accipiter cooperii in Southern Illinois. Transactions of the Illinois State Academy of Science 86: 51-62.
Gallagher, S. 1996. Orange County Breeding Bird Atlas. Sea and Sage Audubon Press, Santa Ana, California.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Cooper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April, 1986. 617 pp.
Hamilton, R. and D.R. Willick. 1996. The Birds of Orange County, California: Status and Distribution. Sea and Sage Press, Irvine, California. 150 pp. with appendices.
Harrison, C. 1978. A field guide to the nests, eggs and nestlings of North American birds. W. Collins Sons and Co., Cleveland, OH. 416pp.
Hays, L. R. 1999. USFWS, pers. obs.
Henny, C. J., and H.M. Wight. 1972. Population ecology and environmental pollution; red-tailed and Cooper's hawks. Pages 229-249 in U.S. Fish and Wildlife Service. Population ecology in migrating birds. U.S. Dep. Inter., Fish and Wildl. Serv. Res. Rep. No. 2. Tech. Paper No. 2831.
Jackman, S. M., and J. M. Scott. 1975. Literature review of twenty-three selected forest birds of the Pacific Northwest. U.S. Dep. Agric., For. Serv., Reg. 6, Portland OR. 382pp.
Meng, H. K. 1951. The Cooper's hawk, Accipiter cooperii (Bonaparte). Ph.D. Thesis, Cornell Univ., Ithaca, NY. 202pp.
Murphy, R. K., M. W. Gratson, and R. N. Rosenfield. 1988. Activity and habitat use by a breeding male Cooper's hawk in a suburban area. J. Raptor Research 22: 97-100.
Patten, Michael. 1998. Riverside County Editor for American Field Notes and Past Secretary, California Birds Records Committee, pers. comm.
Peterson, D. J., and R. K. Murphy. 1992. Prey delivered to two Cooper's hawk Accipiter cooperii nests in northern mixed grass prairie. Canadian Field-Naturalist 106: 385-386.
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Reynolds, R. T. 1975. Distribution, density, and productivity of three species of Accipiter hawks in Oregon. M.S. Thesis, Oregon State Univ., Corvallis. 39pp.
Rosenfield, R. N., and J. Bielefeldt. 1993. Cooper's hawk (Accipiter cooperii). In The Birds of North America, No. 75 (A. Poole and F. Gill, eds.) The Academy of Natural Sciences, Philadelphia, PA and The American Ornithologists' Union, Washington D.C.
Rosenfield, R. N., J. Bielefeldt, J. L. Affeldt and D. J. Beckman. 1995. Nesting density, nest area reoccupancy and monitoring implications for Cooper's Hawks in Wisconsin. Journal of Raptor Research, v.9. n.1, 1995:1-4.
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Siders, M. S., and P. L. Kennedy. 1996. Forest structural characteristics of accipiter nesting habitat: Is there an allometric relationship? Condor 98: 123-132.
Stephenson, John r., and Gena M. Calcarone. 1999. Southern California mountains and foothills assessment: habitat and species conservation issues. General Technical Report GTR-PSW-172. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. 402 pp.
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Whaley, W.H., and C.M. White. 1994. Trends in geographic variation of Cooper's hawk and northern goshawk in North America: A multi variate analysis. Proc. West. Found. Vert. Zool. 5:161-209.
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double-crested cormorant (Phalacrocorax auritus)
State: Species of Special Concern
Federal: None
The double-crested cormorant has a wide distribution throughout the MSHCP Plan Area within suitable habitat. It occurs at every open water body within the Plan Area and thus uses habitat predictably and responds well to available suitable habitat. It will use habitat near open water bodies containing trees for creating rookeries. The only known nesting location in the Plan Area and any nesting locations found in the future will require site specific management.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area 16,100 acres of open water habitat within seven open water bodies and one drainage including Lake Mathews, Diamond Valley Lake, Lake Skinner, Lake Elsinore, Vail Lake, Lake Perris, Mystic Lake and Prado Basin/Santa Ana River and the wetland habitats within Prado Basin/Santa Ana River.
Include within the MSHCP Conservation Area the known double-crested cormorant rookery in the Prado Basin/Santa Ana River.
For the purpose of the conservation analysis, potential habitat for the double-crested cormorant includes open water lakes and reservoirs, drainages supporting open water, and the wetland vegetation communities within the Prado Basin and Santa Ana River where nesting occurs. The double-crested cormorant has been documented to nest within the MSHCP Plan Area at the Prado Basin, and known foraging habitat and potential nesting habitat occur at the large lakes, reservoirs, and drainages supporting open water habitat within the Plan Area. Based on these habitats, the Plan Area supports approximately 18,280 acres of potential habitat for the double-crested cormorant. Table 1 shows the conservation and loss of potential habitat for the double-crested cormorant. Overall, approximately 16,100 acres (88 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public Lands.
As described below under Data Characterization, 22 of the 56 recent point localities have a high location precision. These 22 point locations are distributed throughout the Plan Area within every open water body or drainage containing open water. Of these 22 point localities, 12 will be inside the Criteria Area or Public/Quasi-Public Lands. However, of the ten points located outside these preserved areas, the habitats for which they are mapped include existing residential/ urban/exotic areas, existing agriculture, or other upland habitats. These habitats do not constitute suitable habitat but these locations may have been of a bird flying overhead or within habitat adjacent to one of the reservoirs where they might hunt. Conservation of this species will generally be considered from a landscape perspective because the species is found throughout the Plan Area and is well documented for the type of habitat within which they forage.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
DOUBLE-CRESTED CORMORANT
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| All Bioregions | |||||||
| Open Water | 12,210 | 1,190 | 9,150 | 10,340 | 40 | 1,830 | 1,870 |
| Prado Basin/Santa Ana River | 6,070 | 550 | 5,210 | 5,760 | 0 | 310 | 310 |
| TOTAL | 18,280 | 1,740 (9%) |
14,360 (79%) |
16,100 (88%) |
40 (<1%) |
2,140 (12%) |
2,180 (12%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
In addition to the landscape focus on open water for foraging and nesting there are definable locations for focusing conservation efforts including the Prado Basin and Santa Ana River where nesting is documented to occur. These areas will be essential for conservation of the species and a total of 5,760 acres of wetland habitats located within the Prado Basin/Santa Ana River will be conserved as Criteria Area and Public/Quasi-Public Lands. Any nesting locations, if they were to be identified in the future, will be important to consider for conservation.
In addition, the Riparian/Riverine Areas and Vernal Pools policy described in Section 6.1.2 provides for conservation of wetlands which provide habitat for this species through avoidance and minimization. Mitigation for impacts to wetlands shall be incorporated in accordance with the "No Net Loss" policy of federal and state wetland regulations. The proposed mitigation shall be directly related to the functions and values of the wetland as related to this species and result in equivalent replacement.
Several large blocks of habitat supporting the current known nesting and foraging locations and potential foraging and nesting locations of the double-crested cormorant will be conserved as Criteria Area and Public/Quasi-Public Lands, including the Prado Basin/Santa Ana River, Lake Skinner, Diamond Valley Lake, Lake Mathews, Mystic Lake/San Jacinto Wildlife Area, Lake Perris, Lake Elsinore, Vail Lake, Bautista Creek, San Timoteo Creek, Temecula Creek, Murrieta Creek, and San Jacinto River. As identified below, the dispersal distance for the species, 5 to 10 miles, will allow them to cover the MSHCP Plan Area and they will be capable of dispersing from a nest site to forage in any part of the Plan Area. As such, the MSHCP Conservation Area will provide adequate habitat for foraging during nomadic visits to the area and migratory stopovers as well as habitat containing known and potential nest sites with adequate protection around each nest site and foraging areas during the breeding season. Foraging areas are provided at the open water bodies including Vail Lake, Lake Skinner, Diamond Valley Lake, Mystic Lake, Lake Perris, Lake Elsinore, Lake Mathews, Prado Basin/Santa Ana River. Foraging habitat is also provided in drainages containing open water including Bautista Creek, San Timoteo Creek, Temecula Creek, Murrieta Creek, and San Jacinto River. Potential and known nest sites are provided at these open water/reservoirs and within the MSHCP Conservation Area, especially in the Prado Basin area, in the form of large trees or snags. These MSHCP Conservation Area areas are linked as well, however the double-crested cormorant, due to its ability to move long distances, may rely less on the linkage than other species.
In summary, conservation for this species will be achieved by inclusion of at least 16,100 acres of suitable Conserved Habitat (open water and wetland habitat within the Prado Basin/Santa Ana River) and the known rookery location in the Prado Basin/Santa Ana River. The current population size of the double-crested cormorant is unknown, however it appears to have regular use of specified areas and a known breeding location that has been regularly monitored in the past.
The estimated Take of the double-crested cormorant is based on the acreage of potentially suitable and/or occupied habitat. About 2,180 acres of potential habitat for the double-crested cormorant will be outside the Criteria Area and Public/Quasi-Public Lands and individuals located within these areas will be subject to Incidental Take consistent with the Plan. This comprises approximately 12 percent of the total potential habitat. This includes the open water bodies composed of Hemet Lake, and Lake Riverside.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The UCR location database includes approximately 67 records for the double-crested cormorant within the Plan Area dated from 1900 to 1999. Approximately 56 records are relatively recent (dated from 1990) and of these recent records, 22 are high precision records that can be accurately placed within the area. The habitat types associated with these recent and high precision data records include alluvial, agriculture, riparian, sage scrub, open water, and residential. The residential habitat records may reflect records that are either no longer extant or where the location is a small pocket of suitable habitat within or adjacent to a developed area or a residential area adjacent to an open water body.
The literature available on the double-crested cormorant is relatively low. It is focused on the natural history of the species, however, some of the details of its natural history have not been determined. A few general ornithological reference treatments have been prepared for the species. Little information is available with respect to the Plan Area other than general distribution and occurrence information.
The double-crested cormorant is a common inhabitat of seacoasts and inland waters, rarely observed out of sight of land. They may be seen swimming low in the water, often with little more than their heads and necks showing (Hatch and Weseloh 1999). As summarized by Zeiner et al. (1990), double-crested cormorants require lakes, rivers, reservoirs, estuaries, or use the ocean for foraging. It occupies diverse aquatic habitats in all seasons and requires, in addition to feeding habitats, suitable places for daytime resting or loafing and nighttime roosts (Hatch and Weseloh 1999). Double-crested cormorants nest on the mainland in tall trees, wide rock ledges on cliffs, or rugged slopes near (or in) the aquatic environments. The species rests in the daytime and roosts overnight beside the water on offshore rocks, islands, steep cliffs, dead branches of trees, wharfs, jetties, or even transmission lines. Its perching sites must be barren of vegetation (Bartholomew 1943). It must have nearby access to perches which it visits periodically in the day to dry its plumage. Sometimes it rests, or even sleeps, on the water in the daytime (Palmer 1962). It requires a considerable length of water, or an elevated perch, for a labored and lengthy take-off. For its habitat, the species also requires undisturbed nest-sites beside the water, on islands or the mainland. The suitable nest-site must be within 8-16 kilometers (5-10 miles) of a dependable food supply (Palmer 1962).
Double-crested cormorants breed from Alaska eastward to Newfoundland southward, in isolated colonies, to California, Florida, Mexico and Belize. It is located along the entire Pacific coast from the Aleutians to southern Baja and along the Atlantic coast from Newfoundland south to Florida (Terres 1980). The species winters from Alaska eastward to New England southward to California, Florida, Mexico, and Belize but is absent from the northernmost portion of the breeding range (AOU 1998).
Zeiner, et al. (1990) summarize the distribution, abundance, and seasonality of the double-crested cormorant within California as follows. It is a year-long resident along the entire coast of California and on inland lakes, and seasonally increases in population size as migrant populations winter in the area. During August to May, it is fairly common to locally very common along the coast and in estuaries and salt ponds; it is uncommon in marine subtidal habitats from San Luis Obispo County south, and very rare to the north. In the same season, it is fairly common at the Salton Sea and Colorado River reservoirs, and rare to fairly common in lacustrine and riverine habitats of the Central Valley and coastal slope lowlands. It is less common in the summer, except it is locally common near nesting colonies. In southern California, the species is considered a year-round resident (Garrett and Dunn 1981). Although double-crested cormorants are present in suitable habitats throughout southern California, rookeries are extremely scarce away from the Salton Sea, the Colorado River, and the Channel Islands (Garrett and Dunn 1981).
Although double-crested cormorants may be found year-round nearly throughout the Plan Area in appropriate habitats, there is only one known rookery located in the Prado Basin (L.R. Hays, USFWS, pers. obs.; Michael Patten, Riverside County Editor for American Field Notes and Past Secretary, California Bird Records Committee, pers. comm., 1998). Approximately 40 pairs bred in the Prado Basin during the 1998 breeding season (James Pike, USFWS, pers. comm., 1998). Other localities where the species is regularly observed include Lake Mathews, Lake Perris, Lake Skinner, and Lake Elsinore. These occurrences are likely to be foraging or wintering individuals and they probably use these locations, as well as other lakes/reservoirs, on a regular basis.
Geographic locations recorded within the U.C. Riverside database include: Prado Basin, Santa Ana River, Lake Mathews, Lake Elsinore, Santa Rosa Plateau, Temecula Creek, Lake Skinner, Wilson Valley, Lake Hemet, Lake Perris, San Jacinto Wildlife Area, and San Timoteo Creek.
Genetics: The double-crested cormorant is thought to be closely related to the neotropic cormorant (Hatch and Weseloh 1999). A phylogenetic analysis of osteological characters by Siegel-Causey (1988) placed the double-crested cormorant with the neotropic cormorant and three species from Australia and India in the genus Hypoleucos.
Diet and Foraging: Double-crested cormorants are strictly piscivorous (Robertson 1974, Cogswell 1977, Neuman et al. 1997) and thus require lakes, rivers, reservoirs, estuaries, or the ocean for foraging. Foraging occurs mainly in daylight hours (Blackwell and Krohn 1997). In areas where fish populations are augmented (e.g., trout stocking) feeding is affected. For example, cormorants were found eating mainly suckers (Catastomus spp.) before trout stocking, but trout-consumption increased from 17 percent to 60 percent after stocking (Derby and Lovvorn 1997). Foraging in this species is opportunistic and flexible: more than 250 species of fish from over 60 families have been reported as prey (Hatch and Weseloh 1999). Supply of prey can dictate habitat selection and occurrence of cormorants (Blackwell and Krohn 1997).
While foraging, the double-crested cormorant dives from the water surface and pursues prey underwater, usually remaining submerged for about 30 seconds. It prefers water less than 9 meters (30 feet) deep with a rocky or gravel bottom, but may catch fish as deep as 22 meters (72 feet). Sometimes the species feeds cooperatively in flocks of up to 600 individuals, often with pelicans (Zeiner et al. 1990). It generally feeds in shallow, open water and close to shore. It may feed over sandy bottoms or among rocks and in beds of sea grass or kelp (Hatch and Weseloh 1999).
Daily Activity: Foraging activity of the double-crested cormorant during the winter can occupy, on average, 17.7 percent of a cormorant's daily activity (King, et al. 1995). It frequently rests in the daytime and migrates both day and night (Zeiner, et al. 1990).
Reproduction: Double-crested cormorants nest on the mainland in tall trees near (or in) aquatic environments. Males typically arrive at the nesting area first unpaired. Advertising displays by the males and courtship are evident at the nest site shortly after arrival. Both members of the pair build a new nest, or repair an old one. The nest is often sufficiently complete within two to four days for egg-laying (Hatch and Weseloh 1999). The double-crested cormorant may nest on the ground or cliffs, in trees or shrubs, or on artificial nest structures and transmission line towers, and also on abandoned wharves or on bridges (Hatch and Weseloh 1999). Arboreal nests are placed 0.5 to 30 meters above ground in forks of branches or adjacent to the trunks. Zeiner et al. (1990) summarize breeding information as follows. It breeds mostly from April to July or August, but begins in January at the Salton Sea and Colorado River. Most of the egg-laying is from April to June. The species is monogamous; it nests in colonies of a few to hundreds of pairs, or even thousands; there is little current information on the sizes of California colonies. The clutch size is usually 3-4 eggs, the range is 2-7 eggs, possibly as high as 9 eggs. They are single-brooded. Incubation is 24.5-29 days. The altricial young are tended by both parents, and first fly at 5-6 weeks, and are fully independent at 10 weeks. The number of chicks fledged per nest in several San Francisco populations varied from 0.61 to 1.70 (Stenzel, et al. 1995). The cormorant usually breeds first at 3 years, sometimes at 2 years. About 25 percent of adults at breeding colonies are prebreeders (Lewis 1929, Mendall 1936).
Survival: The oldest banded double-crested cormorant has been recorded as 17 years and nine months (Klimkiewicz and Futcher 1989). Van der Veen (1973) estimated first-year survival of 0.48, second year of 0.74, and subsequent annual suvival of 0.85 with a mean adult life expectancy of 6.1 years. For studies on annual reproductive success, the hatching success is typically 50 to 75 percent; fledging success is 1.2 to 2.4 young per nest or 74 to 95 percent. Chick loss from the hatching to fledging periods is often low, measured at 5 percent in coastal British Columbia (Drent et al. 1964).
Dispersal: During the winter, cormorants move, on average, 15.7 kilometers from their night roost to a foraging location (King, et al. 1995). Individuals do not show fidelity to a roost site however, in stable populations, natal philopatry is probably high (King 1996). New colonies are thought to be formed by young birds, often at sites they have used as roosts or loafing areas, which may be the closest suitable habitat to the natal colony (Hatch and Weseloh 1999). Individuals forage far from the colony or roosts. Birds followed by airplane in Wisconsin flew an average of less than 3 kilometers from the breeding colony to the first foraging site and some individuals flew as far as 30 kilometers (Hatch and Weseloh 1999).
Socio-Spatial Behavior: The double-crested cormorant usually forages within 8-16 kilometers (5-10 miles) of the roost or nest colony (Palmer 1962). In Manitoba, the spacing of ground nests on islands averaged 1 per 0.8 square meters (9 feet) (McLeod and Bondar 1953). The defended territory is reported only at the nest, where a small area is actively defended within beak range (Siegel-Causey and Hunt 1986). The territory is used for some courtship displays, copulation, and nesting; it consists of the nest, and a perch for the non-incubating parent (Palmer 1962). In Saskatchewan, ground nests on islands were 22-38 centimeters (8.5-15 inches) in diameter, and ranged from 0-91 centimeters (0-36 inches) apart, measured from rim to rim (Vermeer 1970).
Community Relationships: The double-crested cormorant may hunt cooperatively with pelicans (Zeiner et al. 1990). The species is generally very gregarious throughout the year. They typically form dense nocturnal roosts, diurnal loafing areas, and breeding colonies (Hatch and Weseloh 1999).
Judging from historical reports of huge migratory flocks blocking out the sun in the Mississippi River Valley (Robbins 1991), the double-crested cormorant has undoubtedly undergone a spectacular population decline in this century. One flight in La Crosse, Wisconsin on 24 April 1926 "continued for two and one-half hours, more or less intermittently, although there were always from a dozen to hundreds of large flocks in the air. The number of birds is variously estimated at from 100,000 to 1,000,000 birds"(Mark Byers, La Crosse Tribune, as quoted in Robbins 1991). By the 1960s, breeding colonies were limited to two counties in Wisconsin and only three to five birds were seen outside the few breeding colonies. By 1973, the species became a candidate for the [Wisconsin] endangered species list. Marked reductions in species numbers and inland breeding colonies in California also were noted as early as the early 1940's (Grinnell and Miller 1944). Although habitat destruction and persecution are implicated in the species' decline, environmental contaminants (such as persistent pesticides) and disease are also problematical, as is evidenced by a recent, massive die-off of the species at the Salton Sea (USFWS, unpublished data). Numbers of the double-crested cormorant have steadily been increasing since about 1975. Explanations arise from lowered mortality from pesticides and from the direct killing that was characteristic of earlier decades, increased food in the breeding season, and enhanced overwintering survival of adults and young (Hatch and Weseloh 1999).
Current declines in Washington, British Columbia and Baja California, may be explained by apparent movements of nesting birds during El Niño oceanographic conditions, habitat loss at interior colonies, and use of artificial nesting habitats (Carter, et al. 1995).
Many nesting colonies in California have been abandoned after human disturbance and habitat destruction (Remsen 1978). In Quebec, human disturbance of breeding colonies caused nest abandonment and increased predation by gulls on eggs and young (Ellison and Cleary 1978). Predation on eggs and young by gulls and crows may be an important factor reducing nesting success (Ellison and Cleary 1978, Siegel-Causey and Hunt 1981).
Currently, the double-crested cormorant may still be perceived as a pest of aquaculture in the southern United States and thus may receive some persecution. Management activities aimed at balancing cormorant and fish populations have been evaluated by researchers as poor and lacking scientific basis (Nisbet 1995). Future management responsibilities will be directed at balancing human interests and wildlife needs (Acord 1995). Owing to their economic impacts in some regions, further investigations are needed under controlled conditions to determine the effects of fish harvest rates by cormorants on overall production in ponds (Erwin 1995). The efficacy of providing alternative wetland feeding sites for cormorants is an area that requires more investigation. Birds may be lured away from catfish farms by nearby created wetlands (Erwin 1995).
The double-crested cormorant rookery in the Prado Basin is one of very few on the coastal slope of southern California away from the sea. The Prado Basin colony and a rookery consisting of approximately 40 pairs at Anaheim Lakes in Orange County apparently are the only breeding areas in or near the Los Angeles Basin (Gallagher 1997).
Increased populations sizes of the double-crested cormorant in the Great Lakes ecosystem have been attributed to a reduction in levels of organochlorine contaminants, reduction in human persecution and an increase in the availability of "forage-base fish" (Weseloh and Ewins 1994). Construction of irrigation reservoirs in Wyoming accounted for large, recent breeding population increases (Findholt 1988). However, these populations may not be sustainable if nest trees or nesting islands either decay or are eliminated by excessively high or low water levels (Findholt 1988).
Acord, B. R. 1995. Cormorant management and responsibilities: United States Department of Agriculture. Colonial Waterbirds 18 (Special Publication): 231-233.
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Bartholomew, G. A., Jr. 1943. The daily movements of cormorants on San Francisco Bay. Condor 45:3-18.
Blackwell, B. F. and W. B. Krohn. 1997. Spring foraging distribution and habitat selection by double-crested cormorants on the Penobscot River, Maine, USA. Colonial Water birds 20:66-76.
Carter, H. R., A. L. Sowls, M. S. Rodway, U. W. Wilson, R. L. Lowe, G. J. McChesney, F. Gress, and D. W. Anderson. 1995. Population size, trends and conservation problems of the double-crested cormorant on the Pacific coast of North America. Colonial Waterbirds 18:189-215.
Cogswell, H. L. 1977. Water birds of California. Univ. California Press, Berkeley. 399pp.
Derby, C. E. and J. R. Lovvorn. 1994. Predation on fish by cormorants and pelicans in a cold-water river: A field and modeling study. Canadian Journal of Fisheries and Aquatic Sciences 54:1480-1493.
Drent, R., G. F. van Tets, F. Tompa, and K. Vermeer. 1964. The breeding birds of Mandarte Island, British Columbia. Can. Field-Nat. 78: 208-261.
Ellison, L. N., and L. Cleary. 1978. Effects of human disturbance on breeding of double-crested cormorants. Auk 95:510-517.
Erwin, R. M. 1995. The ecology of cormorants: some research needs and recommendations. Colonial Waterbirds 18 (Special Publication): 240-246.
Findholt, S. L. 1988. Status, distribution and habitat affinities of double-crested cormorant nesting colonies in Wyoming, USA. Colonial Waterbirds 11: 245-251.
Gallagher, S. 1997. Breeding Bird Atlas (Orange County). Sea and Sage Audubon Press, Santa Ana, California. 264 pp.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Copper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April 1986. 617 pp.
Hatch, J. J. and D. V. Weseloh. 1999. Double-crested Cormorant. Birds of North America 441:1-36.
Hays, L. 1999. Pers. Comm. U.S. Fish and Wildlife Service.
King, D. T. 1996. Movements of double-crested cormorants among winter roosts in the Delta Region of Mississippi. Journal of Field Ornithology 67:205-211.
King, D. T., J. F. Glahn and K. J. Andrews. 1995. Daily activity budgets and movement of winter roosting double-crested cormorants determined by biotelemetry in the Delta region of Mississippi. Colonial Waterbirds 18:152-157.
Klimkiewicz, M. K., and A. G. Futcher. 1989. Longevity records of North American birds. Suppl. 1. J. Field Ornithol. 60: 469-494.
Lewis, H. F. 1929. The natural history of the double-crested cormorant (Phalacrocorax auritus auritus). Ru-Mi-Lou Books, Ottawa. 94pp.
McLeod, J. A., and G. F. Bondar. 1953. A brief study of the double-crested cormorant on Lake Winnipegosis. Can. Field-Nat. 67:1-11.
Mendall, H. L. 1936. Home life and economic status of the double-crested cormorant. Univ. Maine Studies, Second Ser., No. 38. 159pp.
Neuman, J., D. L. Pearl, P. J. Ewins, R. Black, D. V. Weseloh, M. Pike and K. Karwowski. 1997. Spatial and temporal variation in the diet of double-crested cormorants breeding on the lower Great Lakes in the early 1990s. Canadian Journal of Fisheries and Aquatic Sciences 54:1569-1584.
Nisbet, I C T. 1995. Biology, conservation and management of the double-crested cormorant: Symposium summary and overview (The double-crested cormorant: Biology, conservation and management, Colonial Waterbird Society Annual Meeting, University of Mississippi, Oxford, Mississippi, USA, October 14-18, 199). Colonial Waterbirds 18:247-252.
Palmer, R. S., ed. 1962. Handbook of North American birds. Vol. 1. Yale University Press, New Haven, CT. 567pp.
Patten, Michael. 1998. Pers. Comm. Riverside County Editor for American Field Notes and Past Secretary, California Bird Records Committee
Pike, J. 1998. Pers. Comm. USFWS.
Remsen, J. V., Jr. 1978. Bird species of special concern in California. Calif. Dept. of Fish and Game, Sacramento. Wildl. Manage. Admin. Rep. No. 78-1. 54pp.
Robbins, S. 1991. Wisconsin Bird life. The University of Wisconsin Press, Madison. 702 pp.
Robertson, I. 1974. The food of nesting double-crested and pelagic cormorants at Mandarte Island, British Colombia, with notes on feeding ecology. Condor 76:346-348.
Siegel-Causey, D. 1988. Phylogeny of the Phalacrocoracidae. Condor 90: 885-905.
Siegel-Causey, D., and G. L. Hunt. 1981. Colonial defense behavior in double-crested and pelagic cormorants. Auk 98:522-531.
Siegel-Causey, D., and G. L. Hunt. 1986. Breeding-site selection and colony formation in double-crested and pelagic cormorants. Auk 103: 230-234.
Stenzel, L. E., H. R. Carter, R. P. Henderson, S. D. Emslie, M. J. Rauzon, G. W. Page, and P. Y. O'Brien. 1995. Breeding success of double-crested cormorants in the San Francisco Bay area, California. Colonial Water birds 18:216-224.
Terres, J. K. 1980. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf, New York, New York. 1109pp.
Van der Veen, H. E. 1973. Some aspects of the breeding biology and demography of the double-crested Cormorants (Phalacrocorax auritus) of Mandarte Island. Ph.D. thesis, Zoologisch Laboratorium der Rijksuniversiteit te Groningen, Groningen.
Vermeer, K. 1970. Some aspects of nesting of double-crested cormorants at Cypress Lake, Saskatchewan in 1969, a plea for protection. Blue Jay 28:11-13.
Wesloh, D. V. C. and P. J. Evans. 1994. Characteristics of a rapidly increasing colony of double-crested cormorants in Lake Ontario: Population size, reproductive parameters and band recoveries. Journal of Great Lakes Research 20:443-456.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
downy woodpecker (Picoides pubescens)
State: None
Federal: None
The downy woodpecker is sparsely distributed throughout the MSHCP Plan Area within suitable habitat. There are several areas that appear to be Core Areas including Prado Basin/Santa Ana River, Temescal Canyon, Alberhill Creek, Temecula Creek, and the Vail Lake area. It also occurs in other areas of the Plan Area including but not limited to San Timoteo Creek, the Badlands, Potrero, the mountain Bioregions, and Wilson Valley. Because it is well known for using riparian scrub, forest and woodland, and oak woodland and forest, occurs in all Bioregions of the Plan Area with known Core Areas, a landscape level of management with site specific requirements is proposed.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include within the MSHCP Conservation Area at least 34,080 acres of suitable nesting and foraging habitat for the downy woodpecker including riparian scrub, forest and woodland, and oak woodland and forest.
Include within the MSHCP Conservation Area the 5 Core Areas and linkages within the Prado Basin/Santa Ana River (9,670 acres), Vail Lake (Subunit 3 of the Southwest Area Plan; 12,320 acres), Temescal Wash (Subunit 3 of the Temescal Canyon Area Plan; 4,010 acres), Alberhill Creek (Subunit 2 of the Elsinore Area Plan; 3,460 acres), and Temecula Creek (Subunit 2 of the Southwest Area Plan; 850 acres).
Include within the MSHCP Conservation Area the micro-habitat (i.e., groups of large snags) in potential nesting habitat.
For the purpose of the conservation analysis, potential habitat for the downy woodpecker includes riparian scrub, woodland, and forest, and oak woodland and forest habitat in all Bioregions within the Plan Area. The preferred habitat for the downy woodpecker, ecotones rather than forested areas and ecotones with a mixture of forest shrub and grasslands rather than either forest or forest/shrub ecotones (Brenner, et al. 1992) is embedded within the potential habitat analyzed for this species. The vegetation mapping for the Plan Area is not of a suitable fine scale to quantify the specific sub-habitat preferred by the downy woodpecker, however this sub-habitat of ecotones is included with the habitats analyzed for this species. Based on these habitats, the Plan Area supports approximately 46,790 acres of potential habitat for the downy woodpecker. Table 1 shows the conservation and loss of potential habitat for the downy woodpecker. Overall, approximately 34,080 acres (73 percent) of potential habitat in the Plan Area will be conserved in Criteria Area (6,310 acres or 13 percent) or existing Public/Quasi-Public Lands (27,770 acres or 59 percent). Within this potential habitat, areas containing groups of snags which provide the micro-habitat that is preferred by this species will be conserved.
This species occurs within the Forest Service lands as well as the lowland Bioregions as a breeding and wintering species. It occurs predominantly within riparian scrub, woodland and forest, and oak woodland and forest. Under the existing Forest Land allocation plan, these locations and habitats generally are located within the San Jacinto Wilderness area, the San Mateo Canyon Wilderness Area, and in most of the grazing allotments in both National Forests. Although it has been documented to occur in relatively low numbers at the higher elevations (below 2,000 meters) within the San Bernardino and Cleveland National Forest, the downy woodpecker is not documented to have Core Areas within these lands (Garrett and Dunn 1981). However, conservation of riparian and woodland habitats within the Cleveland National Forest and San Bernardino National Forest are important conservation areas for the downy because suitable habitat is present within these areas and it has been recorded within the mountain Bioregions up to 2,000 meters (Garrett and Dunn 1981).
TABLE 1
SUMMARY OF HABITAT CONSERVATION
DOWNY WOODPECKER
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| All Bioregions | |||||||
| Riparian Scrub, Woodland, Forest | 14,610 | 3,920 | 7,270 | 11,190 | 370 | 3,050 | 3,420 |
| Oak Woodlands and Forest | 32,180 | 2,390 | 20,500 | 22,890 | 5,020 | 4,270 | 9,290 |
| TOTAL | 46,790 | 6,310 (14%) |
27,770 (59%) |
34,080 (73%) |
5,390 (12%) |
7,320 (16%) |
12,710 (27%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
In addition, the Riparian/Riverine Areas and Vernal Pools policy described in Section 6.1.2, MSHCP Volume 1, provides for conservation of wetlands which provide habitat for this species through avoidance and minimization. Mitigation for impacts to wetlands shall be incorporated in accordance with the "No Net Loss' policy of federal and state wetland regulations. The proposed mitigation shall be directly related to the functions and values of the wetland as related to this species and result in equivalent replacement.
As described below under Data Characterization, 34 of the 65 relatively recent point localities have a high location precision. Of these 34 point localities, 10 (29 percent) will be inside the Criteria Area and 12 (35 percent) are located within Public/Quasi-Public Lands. One point location (3 percent) will be in the Rural/Mountainous zone. Of the 11 high precision recent points located outside the MSHCP Conservation Area, one point is located within suitable habitat composed of riparian habitat and the balance are located outside suitable habitat areas within existing residential/urban/exotic areas, non-native grassland, croplands, or Riversidean sage scrub. It is likely that many of the point locations are within riparian habitat and some of these may be inside the MSHCP Conservation Area but do not appear to be due to mapping scale. Conservation of this species will be considered from a landscape perspective, especially in the more western lowlands along the Interstate 15/215 corridor. This is largely due to the fact that the suitable habitat has been well defined and providing additional suitable habitat that is not currently occupied may assist with the recovery of the species.
In addition, there are definable locations for focusing conservation efforts that contain the downy woodpecker including Prado Basin/Santa Ana River (9,670 acres), Vail Lake (Subunit 3 of the Southwest Area Plan; 12,320 acres), Temescal Wash (Subunit 3 of the Temescal Canyon Area Plan; 4,010 acres), Alberhill Creek (Subunit 2 of the Elsinore Area Plan; 3,460 acres), and Temecula Creek (Subunit 2 of the Southwest Area Plan; 850 acres). A total of 30,310 acres of Core Areas will be included within the MSHCP Conservation Area. Conservation is also provided in areas that are occupied by the downy woodpecker but that are not Core Areas including San Timoteo Creek, the Badlands, Potrero, Wilson Valley, and drainages and woodland areas within the Cleveland National Forest and San Bernardino National Forest.
Several large blocks of habitat supporting or potentially supporting the downy woodpecker will be conserved as Criteria Area or Public/Quasi-Public designations, including the Core Areas at Prado Basin/Santa Ana River, Temescal Wash, Alberhill Creek, Temecula Creek, and Vail Lake area. Other large blocks of habitat that support locations and/or contain potential habitat for this species will also be conserved including San Timoteo Creek, the Badlands, Potrero, Wilson Valley, and riparian habitat and drainages within the Cleveland National Forest and San Bernardino National Forest. Other areas containing few or old records for the downy woodpecker and contain potential habitat include Lake Mathews-Estelle Mountain, San Jacinto Wildlife Area/Lake Perris, Sycamore Canyon Regional Park, and Lake Skinner. The following large blocks of habitat have not been mapped as containing downy woodpeckers: Bautista Creek, Reche Canyon, Wasson Canyon, upper San Jacinto River, Murrieta Creek, and Santa Rosa Plateau Nature Preserve. However, these habitat blocks may have smaller riparian systems that contain potentially suitable habitat and could be occupied by downy woodpeckers currently or in the future.
As such, the MSHCP Conservation Area will provide adequate habitat linkages between core habitat areas for this species and will include smaller drainages that may support small numbers of the species. The Prado Basin Core Area is linked along the Santa Ana River to San Bernardino and Orange counties. This riparian area is linked to the south by the Temescal Wash to Lake Mathews and Lake Elsinore. Riparian habitat within the Vail Lake area is linked to the Lake Skinner-Diamond Valley Lake area via Tucalota Creek and to the San Bernardino National Forest. The Vail Lake area is also linked to the Santa Rosa Plateau and then to the Cleveland National Forest by the riparian habitat in Temecula Creek. The Badlands area provides a major habitat block that provides a linkage to Potrero Creek, Lake Perris, and the San Jacinto Wildlife Area.
In summary, conservation for this species will be achieved by the inclusion of at least 34,080 acres of suitable Conserved Habitat in the MSHCP Conservation Area. In addition, implementation of Objective 3 for this species will conserve the micro-habitat (i.e., groups of large snags) in potential nesting habitat. Five of the Core Areas of the downy woodpecker are conserved within large blocks of habitat in the MSHCP Conservation Area and additional areas with few or no recorded locations but that contain potential habitat are also conserved.
About 12,710 acres (about 27 percent) of potential habitat for the downy woodpecker will be outside the Criteria Area or Public/Quasi-Public designations, and individuals within these areas will be subject to Incidental Take consistent with the Plan. None of the Core Areas will be outside the MSHCP Conservation Area. Of this, approximately 5,390 acres (12 percent) of potential habitat are located within Rural/Mountainous designation areas. While the Rural/Mountainous areas are not included within the MSHCP Conservation Area and will not be managed for the benefit of wildlife, the anticipated levels of development in these areas will likely be consistent with maintaining some habitat for the downy woodpecker.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The UCR location database includes approximately 84 records for the downy woodpecker within the Plan Area dated from 1888 to 2000. A total of approximately 65 records are relatively recent (within the past 10 years) and of these recent records, approximately 34 are high precision records that can be accurately placed within the area. The habitat types associated with these recent and high precision data records include riparian habitat, residential, cropland, grassland, sage scrub, and chaparral. The residential and more upland habitat records may reflect records that are either no longer extant or that are located in a small pocket of suitable habitat within or adjacent to a developed area or upland habitat.
The literature available on the downy woodpecker is relatively low. It is focused on the natural history of the species, however, due to its secretive nature, some of the details of its natural history have not been determined. A few general ornithological reference treatments have been prepared for the species. Little information is available with respect to the Plan Area other than general distribution and occurrence information.
Downy woodpeckers as a whole may nest in deciduous and mixed deciduous coniferous woodland, riparian woodland, second growth, parks, and orchards (AOU 1998). Within southern California, the species generally nests in deciduous (often willow) woodlands, deciduous growth/oak woodlands, orchards, suburban plantings, and occasionally in conifers (Garrett and Dunn 1981). Grinnell and Miller (1944) previously reported that lowland stream-bottoms constitute the main theaters of activity for this woodpecker. Available water may be a factor for presence of the downy woodpecker (Zeiner et al. 1990). This species is a year-long resident of riparian deciduous and associated hardwood and conifer habitats and orchards. It requires abundant snags, and tree/shrub, tree/herbaceous, and shrub/herbaceous ecotones (Zeiner, et al. 1990). Abundance of downy woodpeckers has been correlated with occurrence of large snags and logs (Stark, et al. 1998). This study showed the species to prefer bottomland hardwood forests during both summer and winter seasons. Another study showed that the species prefers ecotones over forested areas and ecotones with a mixture of forest shrub and grasslands more than either forest or forest/shrub ecotones (Brenner, et al. 1992). The downy woodpecker uses tree and shrub foliage for cover; it also digs cavities for nesting and roosting in deciduous trees (Zeiner et al. 1990).
Downy woodpeckers are resident in appropriate habitats from western and central Alaska eastward to Newfoundland southward to southern California and southern Florida (AOU 1998). Some populations migrate or withdraw to southward areas from the northern part of the range in the fall and winter. Otherwise, the species tends to descend from the higher mountains to winter within lower elevation habitat (Terres 1980).
Zeiner, et al. (1990) summarize the distribution, abundance, and seasonality of the downy woodpecker within California as follows. It is a common, year-long resident of riparian deciduous and associated hardwood and conifer habitats. The downy woodpecker occurs throughout the state, usually below 1,800 meters (5,900 ft). It is absent from southern California desert regions. In southern California, the downy woodpecker is present from Los Angeles County southward and eastward locally through San Bernardino County and Riverside County, south to the vicinity of Temecula, and into northern San Diego County (Garrett and Dunn 1981). The species primarily occurs in the lowlands and foothills and is generally absent in mountainous areas but is known to occur within the montane regions in low numbers (Garrett and Dunn 1981).
Formerly termed locally common (Grinnell and Miller 1944), the downy woodpecker has been more recently noted in southern California as fairly common from Los Angeles or Ventura Counties northwards but extending uncommonly and very locally south to extreme northern San Diego County (Garrett and Dunn 1981).
Downy woodpeckers are primarily confined to the northwestern and southwestern portions of the Plan Area according to Garrett and Dunn (1981). Core areas include the large concentration in the Prado Basin and contiguous reaches of the Santa Ana River. Other Core Areas include Temescal Wash, Alberhill Creek, Temecula Creek and Vail Lake.
Other geographic locations recorded within the U.C. Riverside database include: Lake Mathews, the UCR campus area west of Box Springs, Motte-Rimrock Reserve, San Jacinto River, the Badlands, Murrieta Hot Springs, Lake Skinner, Wilson Creek, Lake Perris, Potrero Creek, and San Timoteo Creek. The downy woodpecker has been recorded to be present at Murrieta Creek, and at Railroad Canyon (Michael Patten, Riverside County Editor for American Field Notes and Past Secretary, California Bird Records Committee, pers. comm., 1998). The downy woodpecker has been recorded in low numbers in the Cleveland National Forest and the San Bernardino National Forest and is documented to occur at these higher elevations in relatively low numbers (Garrett and Dunn 1981).
Genetics: Studies of mitchondrial DNA show little polymorphism between the downy woodpecker and mourning dove (Ball and Avise 1992). The study raises questions concerning currently-held evolutionary structures.
Diet and Foraging: Beetles, ants, caterpillars, and other larvae comprise 75-80 percent of the annual diet of the downy woodpecker. The species also eats cambium, berries and other fruits, nuts and seeds, including dogwood, serviceberry, and poison-oak. The downy woodpecker forages on trunks and branches of small trees, usually 2.7 to 20 meters (9-65 feet) above ground (Jackson 1970). It also forages in shrubs and occasionally tall herbs. The species probes, pecks, gleans for insects and occasionally hawks insects (Bent 1939).
Unlike some other woodpecker species, downy woodpeckers forage on a variety of foods over a large winter home range and do not re-visit cache locations (Volman, et al. 1997). Downy woodpeckers, among woodpeckers, appears to be a generalist in terms of excavation foraging where this species uses more tree species than other woodpeckers (Conner, et al. 1994). Downy woodpeckers also showed a preference of smaller diameter substrates (Conner, et al. 1994).
Daily Activity: As a cold-tolerant species, downy woodpeckers were found to have significantly higher basal and peak metabolic rates during winter than in summer (Linknes and Swanson 1996). Thus they are able to maintain activity in colder areas.
Reproduction: Within southern California, the downy woodpecker generally nests in deciduous (often willow) woodlands, deciduous oak woodlands, orchards, suburban plantings, and occasionally in conifers (Garrett and Dunn 1981). The species seems to prefer aspen for the nest cavity (possibly a softer wood) in areas where that tree species is present (Bent 1939). The downy woodpecker excavates a nest cavity in a snag or dead branch 1.3 to 15 meters (4-50 feet) above the ground. The downy woodpecker uses a nest tree that is at least 23 centimeters (9 inches) diameter breast high (Bent 1939, Lawrence 1967). It usually excavates a new nest cavity each year. This species is characterized as a relatively weak excavator therefore preferring to nest in dead trees or dead tops of live trees or to use extremely soft woods (Harestad and Keisker 1989).
As with most woodpeckers, courtship includes the male drumming on dry, resonant limbs to attract a female (Bendire 1895). Breeding occurs from late March to early September; with a peak nesting activity during May through June. The average clutch is 4-5 eggs; the range is 3-7 eggs. The duration of the incubation period is 12-13 days. Both parents incubate and care for the altricial young. Usually 1 brood is raised per year (Dawson 1923).
Survival: No information is available or was reviewed.
Dispersal: No information is available or was reviewed.
Socio-Spatial Behavior: During wintering, downy woodpeckers form a loose social structure where male-female associations may occur, and individuals are generally seen with two or three conspecifics but no evidence of territorial behavior or permanent pair bonds are observed (Matthysen, et al. 1993). Territory and home range apparently are the same for this species (Zeiner et al. 1990). In Ontario, Lawrence (1967) observed 2 downy woodpecker breeding territories of 2.0 and 3.2 hectares (5 and 9 acres). The downy woodpecker did not occur in small wood lots until the size of the woodlot reached 1.2 hectares (Forman et al. 1976).
Community Relationships: There is potential intraspecific competition for food between male and female downy woodpeckers which is apparently reduced by sexual differences in feeding behavior (Jackson 1970, Kilham 1970). Interspecific competition for food between hairy and downy woodpeckers may be reduced by feeding on different species of trees (Kisiel 1972). In Idaho, Ligon (1970) reported competition for food between white-headed and downy woodpeckers.
The species has almost certainly declined overall due to ongoing destruction of woodland habitats within southern California (Zeiner et al. 1990). Loss of riparian woodlands and snags has caused a decline in numbers in recent decades (Grinnell and Miller 1944). No other threats have been identified within the literature.
The species requires abundant snags, and tree/shrub, tree/herbaceous, and shrub/herbaceous ecotones (Zeiner, et al. 1990). Abandoned snag and tree cavities are used by many other species, thus there is potential for a shortage of snags and tree cavities and resulting competition between species.
Artificial snags (polystyrene) have been placed in forests in an attempt to mimic natural snags. Downy woodpeckers are one of a few species which use the artificial snags for excavation and night roosting; however they do not use them for nesting (Conner and Saenz 1996).
Mechanical strip thinning of aspen is a method of harvesting found to be relatively compatible with both forest-dwelling mammals and birds, including downy woodpeckers (Christian and Hanowski 1996).
Supplementary feeding has been identified as a positive management technique for wintering populations of the downy woodpecker (Grubb and Cimprich 1990).
AOU (American Ornithologists' Union). 1998. Check-List of North American Birds. Seventh Edition. American Ornithologists' Union, Washington, D.C. 829 pp.
Austin, G. T. 1976. Sexual and seasonal differences in foraging of ladder-backed woodpeckers. Condor 78:317-323.
Ball, R. M. Jr. and J. C. Avise. 1992. Mitochondrial DNA phylogeographic differentiation among avian populations and the evolutionary significance of subspecies. Auk 109:626-636.
Bendire, C. 1895. Life histories of North American birds. Vol. 2. Smithsonian Contrib. to Knowledge No. 985. Smithsonian Inst., Washington DC. 518 pp.
Bent, A.C. 1939. Life histories of North American woodpeckers. U.S. Natl. Mus. Bull. 174. 334 pp.
Brenner, F. J., B.E. Fisher, and D. Laferrierre. 1992. Habitat use and differential foraging behavior in the downy woodpecker. Journal of the Pennsylvania Academy of Science 66: 15-17.
Christian, D. P., J. M. Hanowski, M. Reuvers-House, G. J. Niemi, J. G. Blake, W. E. Berguson. 1996. Effects of mechanical strip thinning of aspen on small mammals and breeding birds in northern Minnesota, U.S.A. Canadian Journal of Forest Research 26:1284-1294.
Conner, R. N. and D. Saenz. 1996. Woodpecker excavation and use of cavities in polystyrene snags. Wilson Bulletin 108: 449-456.
Conner, R. N., S. D. Jones and G. D. Jones. 1994. Snag condition and woodpecker foraging ecology in a bottomland hardwood forest. Wilson Bulletin 106:242-257.
Dawson, W.L. 1923. The birds of California. 4 Vols. South Moulton Co., San Diego, 2121 pp.
Forman, R. T. T., A. E. Galli, and C. F. Leck. 1976. Forest size and avian diversity in New Jersey woodlots with some land use implications. Oecologia (Berl.) 26: 1-8.
Garrett, K. and J. Dunn. 1981. Birds of Southern California: Status and Distribution. Los Angeles Audubon Society. 407 pp.
Grinnell, J. and A.H. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna Number 27. Copper Ornithological Club, Berkeley, California. Reprinted by Artemisia Press, Lee Vining, California; April, 1986. 617 pp.
Grubb, T.C. and D. A. Cimprich. 1990. Supplementary food improves the nutritional condition of wintering woodland birds: Evidence from ptilochronology. Ornis Scandinavica 21:277-281.
Harestad, A. S. and D. G. Keisker. 1989. Nest tree use by primary cavity-nesting birds in south central British Columbia [Canada]. Canadian Journal of Zoology 67:1067-1073.
Jacson, J.A. 1970. A quantitative study of the foraging ecology of downy woodpeckers. Ecology 51:318-323.
Kilham, L. 1970. Feeding behavior of downy woodpeckers I. Preference for paper birches and sexual differences. Auk 87:544-556.
Kisiel, D.S. 1972. Foraging Behavior of Dendrocopos villosum and D. pubescens in eastern New York state. Confor 74:393-398.
Lawrence, L. de K. 1967. A comparative life-history study of four species of woodpeckers. Ornithol. Monogr. No. 5. 156 pp.
Ligon, J.D. 1970. Behavior and breeding biology of the red cockaded woodpecker. Aug 87:255-278.
Linknes, E. T. and D. L Swanson. 1996. Seasonal variation in cold tolerance, basal metabolic rate and maximal capacity for thermogenesis in white-breasted nuthatches and downy woodpeckers, two unrelated arboreal residents. Journal of Avian Biology 27: 279-288.
Matthysen, E., D. Cimprich, and T. C. Grubb Jr. 1993. Home ranges and social behaviour of the downy woodpecker in winter. Belgian Journal of Zoology 123:193-201.
Patten, Michael. 1998. Riverside County Editor for American Field Notes and Past Secretary, California Birds Records Committee, pers. comm.
Shackelford, C. E. and R. N. Conner. 1997. Woodpecker abundance and habitat use in three forest types in eastern Texas. Wilson Bulletin 109:614-629.
Stark et al. 1998. A quantitative analysis of woodpecker drumming. Condor 100: 350-356.
Terres, J. K. 1980. The Audubon Society Encyclopedia of North American Birds. Alfred A. Knopf, New York, New York. 1109pp.
Volman, S. F., T. C. Grubb Jr. and K. C. Schuett. 1997. Relative hippocampal volume in relation to food-storing behavior in four species of woodpeckers. Brain Behavior and Evolution 49:110-120.
Zeiner, D. C., W., F. Laudenslayer, Jr., K. E. Mayer, M. White. Editors. 1990. California's Wildlife. Volume 2. Birds. State of California, Department of Fish and Game. Sacramento, California. 731 pp.
ferruginous hawk (Buteo regalis)
State: Species of Special Concern
Federal: Federal Special Concern species; Partners in Flight Priority Bird Species; Species of Management Concern
Other: Audubon Society California Watch List
The ferruginous hawk has a widespread distribution throughout the MSHCP Plan Area within suitable foraging habitat. It occurs within the Plan Area as a transient in the spring and fall and may winter within the area. It does not require specific conditions or locations for nesting because it does not nest in the region. It is an opportunistic predator that may forage anywhere within open habitats in the area.
The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0 which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.
Include with the MSHCP Conservation Area at least 144,120 acres of agriculture (field crops), grassland, cismontane alkali marsh, playa and vernal pool, Riversidean alluvial fan sage scrub, coastal sage scrub, desert scrub, peninsular juniper woodland and scrub, and riparian scrub, woodland, and forest, including 2,690 acres at Mystic Lake/San Jacinto Wildlife Area and 5,520 acres of riparian habitat at Prado Basin/Santa Ana River.
The ferruginous hawk uses predominantly open land including grassland for foraging as well as a wide variety of other habitats, including shrub and scrub habitats (Garrett and Dunn 1981). The ferruginous hawk winters and migrates throughout the MSHCP Plan Area. For the purpose of the conservation analysis, potential habitat for the ferruginous hawk includes agriculture (field crops), grassland, cismontane alkali marsh, playa and vernal pool, Riversidean alluvial fan sage scrub, coastal sage scrub, desert scrub, peninsular juniper woodland and scrub, and riparian scrub, woodland, and forest. The riparian and juniper woodland habitat is included because the species will use the trees in these habitats for roosting and as hunting perches. The scrub habitats are included because they have been recorded hunting within sparse forms of such habitats. The other habitats included above comprise open habitat within which they typically forage. Based on these habitats, the Plan Area supports approximately 401,410 acres of potential habitat for the ferruginous hawk. Table 1 shows the conservation and loss of potential habitat for the ferruginous hawk. Overall, approximately 144,120 acres (36 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public Lands.
As described below under Data Characterization, 25 of the 60 recent point localities have a high location precision. Of these 25 point localities, 8 will be inside the criteria area or public/quasi-public lands. A total of 17 point localities will be outside of the MSHCP Conservation Area. Conservation of this species should be considered from a landscape perspective because the species is found throughout the Plan Area and may occur in a variety of habitats. The main areas within which the species has been observed, Prado Basin/Santa Ana River (including 5,520 acres of riparian habitat within the MSHCP Conservation Area) and Mystic Lake/San Jacinto Wildlife Area (including 2,690 acres of suitable habitat), will be conserved. While there are definable locations for focusing conservation efforts, there do not appear to be Core Areas that will be essential for conservation of the species.
TABLE 1
SUMMARY OF HABITAT CONSERVATION
FERRUGINOUS HAWK
| Vegetation Type | MSHCP Plan Area (Acres) |
Within MSHCP conservation Area | Outside MSHCP conservation Area | ||||
|---|---|---|---|---|---|---|---|
| Criteria Area1 (Acres) |
Public/ Quasi-Public (Acres) |
Total Within MSHCP Conservation Area (Acres) |
Rural/ Mountainous (Acres) |
Outside MSHCP Conservation Area (Acres) |
Total Outside MSHCP Conservation Area (Acres) |
||
| Riverside Lowlands and San Jacinto Foothills Bioregions | |||||||
| Agriculture (field crops) | 117,870 | 6,930 | 9,850 | 16,780 | 710 | 100,380 | 101,090 |
| Grassland | 121,750 | 17,470 | 16,130 | 33,600 | 7,000 | 81,150 | 88,150 |
| Cismontane Alkali Marsh | 10 | 10 | 0 | 10 | 0 | 0 | 0 |
| Playas and Vernal Pools | 7,870 | 3,830 | 2,880 | 6,710 | 0 | 1,160 | 1,160 |
| Riversidean Alluvial Fan Sage Scrub | 5,430 | 2,710 | 1,310 | 4,020 | 160 | 1,250 | 1,410 |
| Coastal Sage Scrub | 133,110 | 43,690 | 27,200 | 70,890 | 19,740 | 42,480 | 62,220 |
| Desert Scrubs | 2,230 | 2,160 | 0 | 2,160 | 40 | 30 | 70 |
| Peninsular Juniper Woodland and Scrub | 930 | 340 | 180 | 520 | 0 | 410 | 410 |
| Riparian Scrub, Woodland, Forest | 12,210 | 3,570 | 5,860 | 9,430 | 180 | 2,600 | 2,780 |
| TOTAL | 401,410 | 80,710 (20%) |
63,410 (16%) |
144,120 (36%) |
27,830 (7%) |
229,460 (57%) |
257,290 (64%) |
| 1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area. | |||||||
Several large blocks of habitat supporting the current known and potential foraging locations of the ferruginous hawk will be conserved as Criteria Area and Public/Quasi-Public including the Prado Basin, Santa Ana River, Lake Mathews-Estelle Mountain, Vail Lake/Wilson Valley, Lake Skinner/ Diamond Valley Lake, Mystic Lake/San Jacinto Wildlife Area and surrounding playa habitat, and the Badlands. Additional areas that provide potential foraging habitat include Sycamore Canyon Regional Park, Lake Elsinore grassland area, Sedco Hills, Box Springs Mountain, Lakeview Mountains, Sage, and foothills of the National Forest lands. As identified above, the species occurs within the MSHCP Plan Area as a transient migrant and wintering resident and as such, the MSHCP Conservation Area will provide adequate habitat for foraging and perch sites. These MSHCP Conservation Area areas are linked as well, however the ferruginous hawk, due to its ability to move long distances, may rely less on the linkage than other species.
In summary, conservation for this species will be achieved by inclusion of at least 144,120 acres of suitable Conserved Habitat including agriculture (field crops), grassland, cismontane alkali marsh, playa and vernal pool, Riversidean alluvial fan sage scrub, coastal sage scrub, desert scrub, peninsular juniper woodland and scrub, and riparian scrub, woodland, and forest. The main areas within which the species has been observed, Prado Basin/Santa Ana River and Mystic Lake/San Jacinto Wildlife Area, will be conserved in the MSHCP Conservation Area. The current population size of the ferruginous hawk is unknown, however the foraging habitat requirements are well defined. The species is moderately predictable in its occurrence and may vary in number within the area from a few to many individuals. It has occurred repeatedly in a number of conserved locations.
About 257,290 acres (64 percent) of potential habitat for the ferruginous hawk will be outside the Criteria Area and Public/Quasi-Public designations and individuals occurring within these areas will be subject to Incidental Take consistent with the Plan.
Data reviewed includes the University of California, Riverside, GIS data base, the California Natural Diversity Data Base (CNDDB), and available literature.
The location database for the ferruginous hawk includes approximately 90 data records from 1900 to 1999. Of these records, approximately 60 are relatively recent (within the past 10 years) and of these 25 are of high precision and may be accurately located within the Plan Area. Approximately five of these high precision records are located within developed areas and although they may no longer exist, they may also represent a wintering or transient bird hunting within a residential area. The rest occur within non-native grassland, alkali playa, riparian, sage scrub, chaparral, field crop lands and other vegetation communities that are likely occupied by the species for foraging during its transient and wintering movements throughout the Plan Area.
A moderate amount of literature is available for the ferruginous hawk because it is a bird of prey and is of generally high interest to the ornithological audience. Most of the literature pertains to general natural history, niche determination, and the buteos in general. Few controlled scientific studies have been conducted; however, some management studies are available. Very little information is available for the Plan Area other than what is available regarding basic distribution information.
The ferruginous hawk is an occupant of open dry country and will perch on badger mounds or hillocks when trees or posts are not available. It requires large, open tracts of grasslands, sparse shrub, or desert habitats with elevated structures for nesting. Its wintering habitat is similar in being open and it may also occur in areas of mixed grassy glades and pineries (Brown and Amadon 1968).
Range-wide, within California, ferruginous hawks winter in open terrain and grasslands of plains and foothills (Grinnell and Miller 1944). Within southern California, including the Plan Area, ferruginous hawks typically winter in open fields, grasslands, and agricultural areas (Garrett and Dunn 1981). It frequents open grasslands, sagebrush flats, desert scrub, low foothills surrounding valleys, and fringes of pinyon-juniper habitats (Zeiner, et al. 1990). It searches for prey from low flights over open, treeless areas, and glides to intercept prey on the ground. It also hovers, and hunts from high mound perches. The ferruginous hawk roosts in open areas, usually in a lone tree or utility pole. It is tolerant of heat; the nest is often unshaded. There are no breeding records from California. The ferruginous hawk nests in foothills or prairies; on low cliffs, buttes, cut banks, shrubs, trees, or in other elevated structures (Zeiner, et al. 1990).
The ferruginous hawk breeds from British Columbia locally eastward to southwestern Manitoba generally southward to Nevada and Texas. The species winters from central and southern parts of the breeding range southward to Baja California and northern mainland Mexico (AOU 1998).
The ferruginous hawk broadly occupies areas where it was reported in historically. Its range has retracted at the edge in Alberta, Saskatchewan, and Manitoba during the early 1900s owing to agriculture and invasion of aspen into remaining prairie habitats. Historically, the ferruginous hawk wintered in the Los Angeles area. Christmas Bird Count data show increases in birds wintering in the eastern portion of the range and in California during the 1980s owing to loss of wintering habitat in the Great Plains (Bechard and Schmutz 1995).
It does not breed in southern California but winters there in interior and coastal areas (Garrett and Dunn 1981). Zeiner, et al. (1990) describe the distribution, abundance, and seasonality of the ferruginous hawk as follows. It is an uncommon winter resident and migrant at lower elevations and open grasslands in the Modoc Plateau, Central Valley, and Coast Ranges. The ferruginous hawk is a fairly common winter resident of grasslands and agricultural areas in southwestern California (Garrett and Dunn 1981). It is casual in the northeast in summer. It is migratory; it generally arrives in California in September and departs by mid-April.
Ferruginous hawks may be found locally in appropriate habitats nearly throughout western Riverside County, which is an important wintering area for this species, especially within the central portion of the Plan Area.
Important wintering areas in southern California as a whole include the Lakeview-Perris area (Garrett and Dunn 1981). Elsewhere, ferruginous hawk habitats occur in the Prado Basin, the Badlands, the Temecula/Murrieta area, Diamond Valley Lake, and Rawson Canyon and environs (Michael Patten, Riverside County Editor for American Field Notes and Past Secretary, California Bird Records Committee, pers. comm., 1998).
Genetics: No subspecies have been recognized for the ferruginous hawk. The historic nomenclature includes numerous abandoned synonyms. Chromosomes in the ferruginous hawk were found to be similar in shape and number to those in the gray hawk, red-tailed hawk, rough-legged hawk, white-tailed hawk, roadside hawk, and Harris' hawk. The chromosome