California Partners in Flight Coastal Shrub-Chaparral Bird Conservation Plan

Species Account for the Coastal Cactus Wren (Campylorhynchus brunneicapillus)

Prepared by Christopher W. Solek and Dr. Laszlo J. Szijj
Biological Sciences Department
California State Polytechnic University, Pomona
September 1999


Section I: Species Account Outline

Subspecies Status

Management Status

Range Maps

Historical References

Current Breeding Distribution

Ecology

Breeding Habitat and Nest Site Characteristics

Population Trend

Demographics

Management Issues

Associated Species

Monitoring Methods and Research Needs

Section II: Action Plan Summary

Scientific References

Appendix 1: Coastal Cactus Wren Distribution-Ventura Co., CA.

Appendix 2: Coastal Cactus Wren Distribution-Los Angeles Co., CA.

Appendix 3: Coastal Cactus Wren Distribution-Orange Co., CA.

Appendix 4: Coastal Cactus Wren Distribution-San Bernardino Co., CA.

Appendix 5: Coastal Cactus Wren Distribution-Riverside Co., CA.

Appendix 6: Coastal Cactus Wren Distribution-San Diego Co., CA.

Section I: Species Account Outline

SPECIES: Coastal Cactus Wren (Campylorhynchus brunneicapillus couesi)

SUBSPECIES STATUS: Taxonomic affiliation of the populations in California have been under debate (Bancroft 1923, Rea and Weaver 1990). Both a coastal and interior population exist in the state, historically connected through the San Gorgonio Pass in Riverside County. (Rea and Weaver 1990). The coastal population is unique in that it occurs exclusively within the Coastal Sage Scrub plant community. The Checklist of North American Birds (American Ornithologists’ Union 1998) currently recognizes all California populations of the cactus wren as Campylorhynchus brunneicapillus couesi, inclusive of both the coastal and interior segments. Rea and Weaver (1990) proposed an alternative subspecies distribution( Figure 1).

A portion of the coastal population, inhabiting southern Orange County, coastal San Diego County, and extreme northwestern Baja California, was proposed for subspecies status in 1986, and described as C.b. sandiegensis (Rea 1986). This designation was not accepted by the American Ornithologists’ Union Committee on Classification and Nomenclature. It was concluded that C.b. sandiegensis represents a intermediate form between C.b. couesi and C.b. bryanti, a recognized subspecies found from San Diego County to northern Baja California, Mexico (Department of the Interior 1994). The range of the C.b. couesi is separated from that of C. b. bryanti by about 150 miles (Bancroft 1923).

Figure 1: Rea and Weaver’s (1990) proposed distribution of the subspecies of the Cactus Wren in the southwestern U.S. and northern Mexico.

MANAGEMENT STATUS: The coastal cactus wren is presently listed as a California State Species of Special Concern and Cleveland National Forest Federal Sensitive (Dudek and Assoc. 2000). In 1993, it was selected as one of three target species in California’s Natural Communities Conservation Planning Program (NCCP) and a surrogate for conservation of Coastal Sage Scrub habitat.

In September 1990, the U.S. Fish and Wildlife Service (USFWS) was petitioned to recognize the San Diego cactus wren (C. b. sandiegensis), as an endangered subspecies pursuant to the Federal Endangered Species Act of 1973. In March 1991 , the U.S. Fish and Wildlife Service announced the initiation of a status review for the coastal cactus wren. Based on the findings of the AOU Committee on Classification and Nomenclature, it was decided that the coastal population of the cactus wren be transferred from Category 2 to category 3B, which includes taxa that do not meet the definition of distinct species under the Endangered Species Act (Department of Interior 1994).

RANGE MAPS:

Figure 2. Cactus Wren Breeding Distribution and Relative Abundance North America 1982-1996 ( Sauer et al 1997) (click here for map)
 
 

  Figure 3. Cactus Wren distribution by southern California county: SD (San Diego), IMP (Imperial), R (Riverside), O (Orange), LA (Los Angeles), SB (San Bernardino), K (Kern), V (Ventura) *Note division between coastal and interior populations (Garret and Dunn 1981) (click here for map)


    I. Historical References:

    Bancroft, G. 1923. Some geographic notes on the Cactus Wren. Condor 25: 165-168.

     Grinnel, J. 1898. Birds of the Pacific Slope of Los Angles County. Pasadena Academy of Sciences, Publication No. II. Pasadena, California.

     Grinnel, J. 1904. Midwinter birds at Palm Springs, California. Condor 6: 40-45.

     Grinnel, J. 1921. The Bryant Cactus Wren not a bird of California. Condor 23: 169.

     Stephens, F. 1904. Cactus Wrens. Condor 6: 51-52.

     Swarth, H.S. 1904. The status of the southern California cactus wren. Condor 6: 17-19.

     Willet, G. 1933. A revised list of the birds of southwestern California. Pacific Coast Avifauna 27: 126.

     Woods, R.S. 1948. Northern cactus wren. In A.C. Bent, United States National Museum, Bulletin 195: 219-231.

    1. Current Breeding Distribution
    Breeding populations of the coastal Cactus Wren have been reported from the following counties in California: Ventura (Appendix 1), Los Angeles (Appendix 2), Orange (Appendix 3), San Bernardino (Appendix 4), Riverside (Appendix 5), and San Diego (Appendix 6) . Orange County contains the majority of the coastal population ( Harper and Salata 1991).

    While not addressed in this report, interior (or non-coastal) populations can be found in desert portions of Los Angeles, Riverside, San Bernardino, as well as most of Imperial, and portions of Kern and Inyo Counties. Cactus wrens are most abundant in these interior, desert regions of the state.

    Coastal populations of the cactus wren occur from southern Ventura county, southeast to the Baldwin Hills and the Palos Verdes Peninsula in Los Angeles County, and east along the southern flank of the San Gabriel and San Bernardino Mountains from the northern San Fernando Valley in Los Angeles County to Mentone in San Bernardino County. Populations also extend south along the coastal slopes and interior valleys west of the Peninsular ranges in western Riverside, Orange, and San Diego Counties to extreme northwestern Baja California, Mexico, in the vicinity of Tijuana and Valle de las Palmas (Harper and Salata 1991).

    BBS surveys have shown that smaller numbers extend onto the coastal slope in the uppermost Santa Clara River drainage, in the vicinity of Acton and Agua Dulce. Populations are also reported from the San Fernando Valley (Big Tujunga Wash, Los Angeles County) and the Camarillo/Moorpark area of Ventura County (Garrett, pers.com.). A nearly continuous population occurs along the western flank of the Santa Monica Mountains from Point Mugu north to the Camarillo Grade and east to Newbury Park (Garret 1991). Most populations in Ventura County are found within the Calleguas Creek watershed (Wehtje, pers, comm). Intensive surveys have been conducted in southern Orange and San Diego Counties (Rea and Weaver1990, Tutton et al 1991, Ogden Environmental and Energy Services 1992, Jones and Stokes 1993).

    ECOLOGY:

    1. Average territory size: Anderson and Anderson (1973) found territories of Arizona populations C. brunneicapillus ranging from 1.2 to 2.8 ha, with an average of 1.9 ha. Rea (1990) described territory sizes in San Diego County, California, ranging from 0.8 to 2 ha, with an average of 1.3 ha. Steintz et al (1997) found territories on Camp Pendleton, California ranging from 0.5-2 ha.

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    3. Time and occurrence of seasonal movements: C. brunneicapillus is resident throughout its range in California and does not migrate or make long distance seasonal movements.
    4. Migration stop-over needs/characteristics: Not applicable, as this is a non-migratory species.

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    6. Nest Type: The nest is a bulky, domed structure, constructed of grasses, twigs, leaves, and other plant fibers. It contains a tube-like entrance that can be up to 15 cm (6 in.) long. The inside of the nest is lined with feathers and down from cactus wrens and other bird species. Nests are constructed year-round and used for both roosting and nesting. A single bird can build multiple nests. Cactus wrens often orient the entrance of the nest to take advantage of convective ventilation provided by prevailing winds (Austin 1974, Facemire et al 1990).

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    8. Foraging Strategy: The cactus wren is described as a shrubbery skulker, foraging primarily on the ground or low in the vegetation for insects. Open ground is ignored during periods of greatest heat stress, with the species preferring to forage on shady ground or in the lower branches of midstory vegetation at these times (Ricklefs and Hainsworth 1968). Foraging techniques appear to vary seasonally (Miles 1990).

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    10. Displays: Coordinated breeding displays include tail fanning and wing lifting by both the male and female. Vocalizations can include a simple, non-ritualized duet between the sexes (Freeman 1994).

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    12. Social Organization: Monogamous and reported to mate for life (Anderson and Anderson 1973). Cactus wrens can occur in family groups from late spring through winter, but the juveniles are driven off by the adults as the breeding season approaches (Weathers 1983). Some instances of nest helping, with juveniles from a first brood assisting with the care of a second brood, have been reported (Skutch 1935, Anderson and Anderson 1973).
    13. Clutch Size: 3-5 eggs
    14. Incubating Sex: Female

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    16. Incubation Period: 16 days

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    18. Nestling Period: 19-23 days

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    20. Development at Hatching: The altricial, nidicolous nestlings are totally dependent on the adults for the first three weeks of life. Nestlings eyes open at 6- 8 days. Feathers begin to break sheaths at approximately 8 days. Fledgings attain adult weight by approximately 38 days, and are fully independent at approximately 30-50 days after hatching (Harrison 1978, Anderson and Anderson 1973).

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    22. Number of Broods: One, possibly two, per season in coastal California . Anderson and Anderson (1973) found some Arizona populations producing up to three broods in one season.
    23. Who Tends the Young: female and male
    24. DIET:
    A. Major Food Items (by season): The diet of the cactus wren consists primarily of insects year-round. Bent (1948) summarized food habit data for cactus wrens taken from southern California during July through January and found that 83 % of all stomach samples (n = 41) consisted of animal matter: 27% beetles, 27% hymenoptera (wasps, bees, and ants), 15% grasshoppers, 5% hemiptera (bugs), 5% lepidoptera (caterpillars) and 3% spiders. Vegetable matter made up 17% of all stomach contents and consisted of fruitpulp (13%) from cactus (Opuntia sp.), elderberry (Sambucus sp.) and cascara (Rhamnus sp.) and seeds (4 %) from sumac (Rhus sp.), filaree (Erodium sp.) andfiddleneck (Amsinckia sp.). Plant matter may become more important during the cooler months when some animal items are unavailable.

    Anderson and Anderson (1973) found that animal matter comprised 96.3 % of cactus wren gizzard contents (n=12) collected from March through October in Arizona and 90.1 % of all gizzards (n=5) form November through February.

    1. Drinking: No data exists on free water consumption in California populations, but thespecies presumably obtains the majority of its water from its diet. Anderson and Anderson (1973) report that adult cactus wrens in Arizona infrequently drink free water in July and August, although immature birds were observed drinking water in August. Adults begin to drink free water in September, and the rate of consumption apparently increases to high levels in December and January. Ricklefs and Hainsworth (1968) stated that the cactus wren relies exclusively on water obtained from its food during the period of greatest heat stress.
    XVI. Wintering Ground Needs and Distribution: There appears to be some northward expansion in distribution for this species during the winter months (Fig. 4). This is most likely related to limited winter dispersal to alternate foraging locations. Wintering ground requirements are assumed to be similar to breeding ground needs.

    Fig.4. Cactus Wren Winter Distribution and Relative Abundance (Sauer et al 1997) (click here for map)


    BREEDING HABITAT AND NEST SITE CHARACTERISTICS

    I. Overview of Breeding Habitat :

    Coastal populations of the Cactus Wren are obligate inhabitants of Coastal Sage Scrub, a natural vegetation community of low, semi-woody vegetation found only in coastal and near-coastal portions of the state, generally below 3000 ft.. While some coastal birds have been observed using riparian woodland areas below 2000 ft., it is unlikely that this habitat type is used for nesting. (Gallager 1997).

    Table 1. Mean Abundance of Cactus Wrens by California Physiographic Region (Sauer et al 1997)

    Physiographic Region Mean

    Abundance

    California Foothills
    0.2
    So. Cal. Grasslands
    5.4
    Sonoran Desert
    8.1
    Mojave Desert
    8.0
    Great Basin Desert
    0.3

     

    Areas supporting Coastal Sage Scrub are dry, generally receiving 14 in. of rainfall annually, concentrated in the spring months (Guthrie 1974). Plant species diversity is relatively high, and includes such shrub species as Buckwheat, Eriogonum fasiculatum; California Sagebrush, Artemisia californica; White Sage, Salvia apiana; and Black Sage, Salvia mellifera. Prickly Pear and Cholla Cacti, Opuntia spp. are dominant components of this vegetation type in certain regions of the state. Characteristic trees and tree-like shrubs can include California Black Walnut, Juglans californica, Elderberry, Sambucus mexicana, Laurel Sumac, Malosma laurina, and Lemonade Berry, Rhus integrifolia.

    1. Nest Site
      1. Substrate: Coastal cactus wrens nest almost exclusively in prickly pear (Opuntia littoralis and O. oricola) and Coastal Cholla (O. prolifera). Coastal Cholla is the typical choice in southern San Diego County, where large prickly pears are scarce (Rea and Weaver 1990). Two reports of nests found in Yellow Bush Penstemon (Keckiella antirrhinoides) exist from San Diego County, CA (Rea and Weaver 1990).
      2. Height of nest: Averaging 1 m (3 ft.) above ground level.
      3. Height of plant: Averaging 1.2-1.5 m ( 4-5 feet).
      4. Nest concealment: Nests are placed in relatively conspicuous, unconcealed locations, but are afforded protection by being built within Opuntia cacti patches and are therefore difficult to approach and access.
    1. Vegetation surrounding the nest:
      1. Canopy cover: Nests are built in relatively open, Opuntia scrub areas with little or no canopy cover. While this factor does not appear to directly affect selection of nesting sites, some reports suggest that numerous large shrubs (> 2 m) reduce the desirability of the habitat for this species (Wheeler 1997).
      2. Dominant plant species in canopy: When a taller canopy vegetation is present in Coastal Sage Scrub habitats, California black walnut, Juglans californica, and Elderberry, Sambucus mexicana are the dominant species. Coast Live Oaks (Quercus agrifolia) and California Sycamore (Platanus racemosa) may also occur in the vicinity of nests.
      3. Average shrub cover: Shrubs and shrub-like vegetation, such as cacti, are the dominant component of the cactus wren’s habitat. Wheeler (1997) found O. littoralis cover ranging from 27.3 % to 63.1 % (mean = 40.1 %) at four different sites in Los Angeles County supporting a population of cactus wrens. Shrub cover is important in providing shade and cooler microhabitats, which cactus wrens use when temperatures within desert habitats are high (Ricklefs and Hainsworth 1968a).
      4. Dominant shrub species: California buckwheat, Eriogunum fasiculatum,: California sagebrush, Artemesia californica, prickly pear and Coastal Cholla Opuntia sp.; California Encelia, Encelia californica.
      5. Average forb cover: Herbaceous annuals during the spring and early summer comprise the dominant forb cover around Cactus Wren nests. Unlike the chaparral plant community, Coastal Sage Scrub contains a persistent herbaceous understory that remains an important part of the total cover (greater than 20 %) for twenty years or more following fire (DeSimone 1995). Wheeler (1997) found that herbaceous annuals comprised from 6.9 % to 39.8 % of the forb cover at four different sites.
      6. Dominant forb species: Mimulus sp., herbaceous annuals
      7. Ground cover: Dead vegetation and bare ground/rock are the predominant ground cover around Cactus Wren nests. Wheeler (1997) found dead vegetation to cover from 1.8 % to 9.6 % and bare earth and rocks to cover from 1.2 % to 12.2 % of the surface at four different sites.
      8. Slope: Nests have been observed on slopes ranging from zero to 45 degrees. Rea and Weaver (1990) found territories corresponding to the down slope flow of narrow draws in San Diego County.
      9. Aspect: The most favorable nest locations appear to be on southern or southwesterly facing slopes where Opuntia cacti are most dominant. (Rea and Weaver 1990, C. Solek, pers. obs.) .
      10. Tree DBH: Not applicable, as this species does not nest in trees (at least in coastal California).
      11. Snags: Individuals have been observed using snags, fence posts and fence lines for calling and display.
      12. Distance to water: No information. As this species is found exclusively in arid to semi-arid habitats, access to natural sources of free water is likely to be very limited.
    1. Landscape Features:
      1. Elevation: Coastal populations typically inhabit areas from 0-150 m. There are some reports of coastal birds sighted at 400-450 m. (Rea and Weaver 1990).

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        B. Fragmentation: This is a concern for the coastal populations of C. brunneicapillus inCalifornia, but empirical data on the effects of this fragmentation are limited. Mostcoastal populations are now isolated due to urbanization of the region and persist inhighly fragmented habitats. Isolated populations of birds in Coastal Sage Scrub have been shown to have high rates of extinction (Soule et al 1988), and cactus wrens mayhave difficulty in crossing urbanized areas to repopulate remnant parcels of suitable habitat. Population viability analyses suggest that the small size of these subpopulations coupled with habitat fragmentation may constrain the long-termviability of the metapopulation (Ogden Environmental and Energy Services 1992). Geographic isolation of coastal and interior populations has also been enhanced byurbanization, and may be facilitating genetic differentiation among these segments ofthe population (Rea and Weaver1990, Eggert 1996).

      3. Disturbance (natural or managed): Disturbance from habitat loss and degradation is due primarily to suburban housing developments and the accompanying loss of the Coastal Sage Scrub plant community in coastal southern California.Fire (both of natural and anthropogenic origins) is also a concern. Bontrager etal (1995) found that cactus wrens may have difficulty recolonizing burnedareas of Coastal Sage Scrub, since the species requires cactus of at least 1 meter tall and cactus recovery after a fire can be slow. Benson (1969) considered fire to be the chief limiting factor in the distribution of native cactus in southern California, a fact that would obviously affect the distribution of coastal populations in the region. Incidental fires related to militaryactivities have also contributed to habitat destruction, especially in and around CampPendleton Marine Corps Base, San Diego County (Rea and Weaver 1990, Harper andSalata 1991).Degradation of cactus wren habitat due to city/county weed abatement projects, legaland illegal grading/clearing activities, and recreational activities has beendocumented (Harper and Salata 1991).
      4. Adjacent land use: suburban development, agriculture and grazing
    SPECIAL FACTORS: Factors influencing a species occurrence and viability.
    1. Brood parasitism: None reported. Anderson and Anderson (1973) observed Curved-bill thrashers (Toxostoma curvirostre) destroying cactus wren roosting nests, but never breeding nests, in Arizona. No evidence of this activity with California thrashers (Toxostoma redivivum) exists from coastal California.

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    3. Dietary: no information

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    5. Sensitivity to human-induced disturbance: Nesting can occur close to roads and human habitations as long as the requisite vegetation for nesting and foraging exists (Solek, pers. obs., Eggert 1996, Wheeler 1997). Nests can be inspected and nestlingshandled without abandonment by adults. Destruction of Coastal Sage Scrub tends toeliminate the cactus wren from an area, with most populations unable to adapt to mostsuburban conditions (Guthrie 1974).

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    IV. Pesticide use: No information. Populations of this species can occur in closeproximity to agricultural and suburban areas. Permissive use of industrial andresidential pesticides may negatively impact populations by reducing the native insect fauna on which the cactus wren feeds.

    V. Predators: Cooper’s hawks (Accipter cooperii), American kestrels (Falcosparverius), roadrunners (Geococcyx californianus), snakes, woodrats. Aggressive interactions with Scrub Jays( Aphelocoma coerulescens) and Northern Mockingbirds (Mimus polyglottus) have been observed.

    VI. Exotic species invasion/encroachment: feral cats, rats

POPULATION TREND:

No definitive trends are evident from Breeding Bird Survey results (based on population counts throughout the species’ range in North America), but coastal populations have been severely impacted by development throughout southern California (Ogden Environmental and Energy Services 1992, Garret 1991, Wehtje, pers. comm.). The decline of the coastal segment of the cactus wren population in the region is indicative of the significant loss of the Coastal Sage Scrub plant community. Based on information from historical accounts, the species has been extirpated from several locations where it previously bred (Dawson 1923, Willet 1933, Grinnel and Miller 1944). Dramatic declines have been documented in San Diego and Orange Counties (Rea and Weaver 1990). Several of these populations described by Rea and Weaver have been extirpated since the study was conducted (Eggert 1996).The population in the Baldwin Hills, Los Angeles County, is declining and may be extirpated. (Garret pers. com). Ventura County populations have been severely impacted by development (Wehtje, pers. comm.).

Figure 5. Annual Index of Change in Relative Abundance (1966-1996) Cactus Wren-North America (Sauer et al 1997) (click here for map)


Fig. 6. Annual Index of Cactus Wren Abundance Trend Graph-California 1968-1996 (Sauer et al 1997) (Click here for graph)


DEMOGRAPHICS:

  1. Age and sex ratios: No information; sexes are monomorphic, so intensive behavioral observations and mist netting programs during the breeding season are necessary to determine both age and sex ratios for any population. Mist netting as a means to establish age and sex ratio ratios has the potential to bias any estimates, as juvenile cactus wrens are caught more frequently than adult birds, and territorial males more frequently than females (Solek, pers. obs.).
  2. Productivity measure: Atwood (1998) found that the mean number of fledglings produced per pair per year (1993-1997) ranged from 3.0 to 3.63 on the Palos Verdes Peninsula, but a small sample size precluded any statistical analysis of year to year variation. Anderson and Anderson (1973) determined a coefficient of variation of annual productivity at 26.5 percent (mean= 4.3 fledglings per pair). Nest counts alone are not a reliable indicator of population, as individuals tend to build multiple nests( Rea 1990, Solek, pers. obs).
  3. Survivorship:

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    Nestling- Ricklefs (1968) calculated nestling survival rate at 99.35 percent per day (n = 49 nests). Anderson and Anderson (1973) found an overall nestling survival rate of 99.03 percent per day (n = 55).

    Juvenile- Atwood (1998) found that survivorship of juveniles ranged from 9.1percent (n = 44 initially banded) to 75 percent (n = 12), with a mean survivorship of 32 percent from 1992-1997. Ricklefs (1968) reported a daily juvenile survival rate between 99.33 and 99.40 percent (n = 39), and concluded that survival rates for juveniles are comparable to those of nestlings and that the period of lifefollowing fledging does not represent a time of maximum mortality. Anderson and Anderson (1973) reported juvenile survival to be about 50 percent after one month of age and less than 15 percent beyond two months of age (n = 55). Simons and Martin (1990) reported juvenile survival rates after four to six weeks to be48.5 percent (n = 33) and 20.5 percent (n = 34) during two different years.

    Adult- Atwood (1998) found that adult survivorship ranged from 57.4 percent to 73.7 percent for the coastal population on the Palos Verdes Peninsula (1992-1997).It should be mentioned that these values are based on extrapolation of survivorship from subsequent sightings, which may produce a bias toward higher survivorship estimates. Anderson and Anderson (1973) reported an overall survival rate of 50.6 percent over a six-year period. The coefficient of variation in annual adult survivalrate was 42.7 percent over a four years, with a mean survival rate of 52.8 percent per year. Less than 11 percent (n = 74 ) of this banded population survived to breed more than three seasons.

  5. Dispersal: Information on the dispersal capacity of coastal cactus wrens is very limited. Short-distance dispersal to alternate foraging grounds may occur during the winter months, but adult birds are highly sedentary and tend to return to same breeding territory each year. The dispersal capacity of coastal cactus wrens may be sufficient to allow for a moderate (e.g. about 1 %) migration rate between adjacent populations (Ogden Environmental and Energy Sevices 1992).
Movements of 10 km.or greater probably occur very infrequently (Atwood, pers. com.). Atwood (1998) found the mean dispersal distance of juvenile cactus wrens from their natal territory was 1.59 km. (s.d. = 2.28, n = 71) on the Palos Verdes Peninsula, though it should be noted that this is now an extremely isolated population with limited dispersal options to alternate foraging/breeding sites. Data based on Arizona populations suggest that juvenile female cactus wrens disperse farther away from their natal territories than juvenile males (Anderson and Anderson 1973).

MANAGEMENT ISSUES:

Loss and degradation of Coastal Sage Scrub are the immediate management issues affecting coastal populations of C. brunneicapillus in southern California. The loss of this plant community in the region has been substantial, with estimates ranging from a sixty-six to ninety percent loss due to development and agricultural displacement (O’Leary 1995). The absence of regulatory mechanisms, either at the local, county, state, or Federal level, adequate to protect the coastal cactus wren and its habitat, may be the most significant factor responsible for the current situation facing the species (Harper and Salata 1991).

Habitat fragmentation is also a concern. The interior, desert population was historically connected to the coastal population through the San Gorgonio Pass in Riverside County, but now the ranges of these two populations appear to be geographically disjunct as a result of continuing urbanization of the corridor (Rea and Weaver 1990). Fragmentation of coastal habitat may also be facilitating genetic divergence of the now isolated coastal populations (Eggert 1996). Small population size coupled with fragmentation may compromise long-term viability of species by increasing genetic homozygosity and lowering species fitness (Ogden Environmental and Energy Services 1992).

Eggert (1996) suggested that a management plan for the species recognize the fact that certain populations of coastal birds are genetically distinct from the populations in Mexico, as well as those of the California desert. Translocations of individuals between sites should be considered only if suitable habitat does not contain a resident cactus wren population. Combining birds from genetically distinct populations could result in outbreeding depression.

Habitat restoration may be a management option in some cases. Further studies are needed to determine if enhancing and/or improving degraded habitat (e.g. translocation of mature Opuntia cacti to appropriate areas) would benefit the species. At this point in time, protection of the remaining Coastal Sage Scrub habitat appears to be the most efficient and viable strategy for species management.

ASSOCIATED SPECIES:

Avian species: California gnatcatcher ( Polioptila californica californica), Costa’s hummingbird (Calypte costae), Bewick’s Wren (Troglogytes bewickii), California Thrasher (Toxostoma redivivum), Non-avian species: Orange-throated whiptail lizard (Cnemidophorous hyperythrus), Stephen’s kangaroo rat (Dipodomys stephensi

MONITORING METHODS AND RESEARCH NEEDS:

It is clear that intensive demographic and life history studies, focusing on reproductive success, survivorship, and dispersal capacity of this species are needed. The considerable difficulty associated with field studies of the cactus wren makes this type of data difficult and labor intensive to gather

Surveys and/or annual monitoring of the various populations throughout southern California are needed. This would allow for identification of threatened breeding populations and habitat areas. This is especially urgent for the counties where populations have been least studied and are most susceptible to large-scale habitat loss.

Section 2:

Action Plan Summary.

STATUS

While the coastal Cactus Wren is not currently on any state or Federal lists, the population is declining throughout its limited range in southern California. A nominate coastal population, C. b. sandiegensis, proposed for Federal threatened status in 1991, was declined for listing in 1994.

HABITAT NEEDS

Coastal Sage Scrub with patches of tall Opuntia cacti for nesting and breeding. This coastal population appears to nest almost exclusively in Opuntia cacti of at least 1 m in height. Protection of habitat areas with this vegetation type and structure should be a high priority.

CONCERNS

Habitat loss, degradation, and fragmentation are the most critical management issues facing this species. Although the species appears capable of sustaining breeding populations in small, fragmented areas containing suitable habitat, isolation of coastal populations due to urban fragmentation may be promoting loss of genetic variation within these smaller populations and compromise long-term metapopulation viability. Lack of demographic data on the species in California, accompanied by large-scale habitat destruction, will make it difficult to identify threatened populations and implement management plans in a timely manner.

OBJECTIVES

Protection of the remaining Coastal Sage Scrub habitat in Californiais crucial for preservation of coastal populations of the cactus wren. Necessary actions should be taken to improve habitat protection and conservation efforts on a county-wide and regional scale. Long-term demographic and behavioral studies of this species in California are needed and should be encouraged through research by federal, state, and academic institutions.

ACTION

SCIENTIFIC REFERENCES AND LITERATURE CITED:

American Ornithologists’ Union. 1998. Checklist of North American Birds. 7th ed. Am. Ornithological Union, Washington, D.C.

Anderson, A.H. 1934. Cactus Wrens and Thrashers. Bird Lore 36: 108-109.

Anderson, A.H. 1934. A Cactus Wren roosting in a Verdin’s nest. Bird Lore 36: 366.

Anderson, A.H. and A. Anderson. 1946. Notes on the use of the creosote bush by birds. Condor 48: 179.

Anderson, A.H. and A. Anderson. The Cactus Wrens on the Santa Rita experimental range, Arizona. Condor 67: 344-351.

Anderson, A.H. and A. Anderson. 1973. The Cactus Wren. Univ. Ariz. Press, Tucson.

Antevs, A. 1946. Cactus Wrens use "extra" nest. Condor 49: 42.

Anthony, A.W. 1895. Bird of San Fernando, lower California. Auk 7: 134-143.

Atwood, J.L. 1998. Studies of California gnatcatchers and cactus wrens in southern California. Manoment Center for Conservation Sciences and the University of California, Irvine. 42 p.

Austin, G.T., E. Yensen, and C.S. Tomoff. 1972. Snake predation on Cactus Wren nestlings. Condor 74: 492.

Austin, G.T. 1974. Nesting success of the Cactus Wren in relation to nest orientation. Condor 76: 216-217.

Austin, G.T. and R.E. Ricklefs. 1977. Growth and development of the Rufous-winged Sparrow. (Aimophila carpalis). Condor 79: 37-50.

Bailey, F.M. 1922. Cactus Wrens’ nests in southern Arizona. Condor 24: 163-168.

Bancroft, G. 1923. Some geographic notes on the Cactus Wren. Condor 25: 165-168.

Bancroft, G.. 1946. Geographic variation in the eggs of Cactus Wrens in lower California. Condor 48: 124-128.

Beal, F.E.L. 1907. Birds of California in relation to the fruit industry. USDA Biological Survey-Bulletin 30: 64-65.

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Brown, J.L. 1987. Helping and communal breeding in birds: ecology and evolution. Princeton University Press, Princeton, NJ.

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M.S. thesis, New Mexico State University, Las Cruces.

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Grinnell, J, 1921. The Bryant Cactus Wren not a bird of southern California. Condor 23:169.

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Hubbard, L.J. 1976. Learning in foraging efficiency by captive

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M.S. thesis, Arizona State University.

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Miles, D.B. 1990.The importance and consequences of temporal variation in foraging behavior. Studies in Avian Biology 13: 210-217.

Miller, A.H. 1936. Tribulations of thorn-dwellers. Condor 38: 218-219.

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Ogden Environmental and Energy Services Co., Inc. 1992. Population viability analysis for coastal cactus wrens within the MSCP Study Area (draft). Prepared for The Clean Water Program., City of San Diego, 16 p.

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Ricklefs, R.E. 1966. Behavior of young Cactus Wrens and Curve-billed Thrashers. Wilson Bull. 78: 47-56.

Ricklefs, R.E. and F.R. Hainsworth. 1966. The temporary establishment of dominance between two hand-raised juvenile Cactus Wrens (Campylorhynchus brunneicapillus). Condor 69: 528.

Ricklefs, R.E. 1967. A case of classical conditioning in nestling Cactus Wrens. Condor 69: 528-529.

Ricklefs, R.E. 1968. The survival rate of juvenile Cactus Wrens. Condor 70: 388-389.

Ricklefs, R.E. and F.R. Hainsworth. 1968a. Temperature dependent behavior of Cactus Wrens. Ecology 49: 227-233.

Ricklefs, R.E. and F.R. Hainsworth. 1968b. Temperature regulation in nestling cactus wrens: the development of homeothermy. Condor 70: 121-127.

Ricklefs, R.E. and F.R. Hainsworth. 1969. Temperature regulation in cactus wrens: the nest environment. Condor 71: 32-37.

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Appendix 1. Coastal Cactus Wren Distribution-Ventura County, CA

Locality
Site
Source
Year
Method 
Camarillo Round Mtn.-near CSU Channel Islands W. Wehjte
1999
1
Camarillo vicinity of Pt. Mugu Garret*
1991
1
Camarillo/Oxnard Plain W. Potrero Road (north side) W. Wehjte
1999
1
Moorpark (west) Balcolm Canyon Road (Unocal property) W. Wehjte
1999
1
Newbury Park Conejo Grade (north of Hwy. 101) W. Wehjte
1999
1
Santa Rosa Valley south of 118 Fwy/west of Hwy 23 W. Wehjte
1999
1
Simi Valley Alamos Canyon Road W. Wehjte
1999
1
Simi Valley Tijerra Rejada Rd. (north side) W. Wehjte
1999
1
Thousand Oaks west of California Lutheran Church M. Long*
1991
1

* Harper and Salata (1991); 1= Expert Opinion, 2= Point Count, 3= Mist Netting, 4= Nest Searching,
5= Spot mapping, 6= Area Search, 7= Breeding Bird Atlas, 8= BBS Route, 9= Other/Local Opinion

Appendix 2. Coastal Cactus Wren Distribution-Los Angeles County, CA (modified from Harper and Salata 1991)

Locality
Site
Source
Year
Method 
Baldwin Hills
**
Garret
1991
1
Claremont  below San Antonio Dam Guthrie, Wheeler
1997
1
Claremont  below Thompson Creek Dam Guthrie 
1989
1
Claremont  Ranch Santa Ana Botanic Gardens Guthrie
1990
1
Duarte San Gabriel Wash Garret
1991
1
Duarte  west of Fish Canyon Garret
1991
1
Glendora southern slopes of San Jose Extension Guthrie, Wheeler
1997
1
Irwindale  Santa Fe Dam, San Gabriel River Pepin, Wheeler 
1991, 1997
1
La Puente San Jose Hills McKernan
1991
1
Laverne
**
Oglesby
1989
1
Malibu
**
Guthrie 
1989
1
Palos Verdes Palos Verdes Peninsula Atwood 
1998
2, 3, 4
Pomona/San Dimas inclusive of Bonelli Regional Park Garret
1991
1
Puente Hills
**
Garret, Guthrie
1991, 1989
1
San Dimas Bonelli Regional Park Garret, McKernan, Wheeler 
1991, 1997
1
San Dimas Raging Waters Theme Park Guthrie
1989
1
San Dimas  San Dimas Canyon Park Guthrie
1989
1
San Fernando Valley Big Tujunga Wash Garret, Pepin 
1991
1
San Jose Hills Cal Poly Pomona Solek
1999
2, 3, 4
Walnut San Jose Hills McKernan
1991
1
West Covina San Jose Hills McKernan
1991
1

** No specific site specified; 1= Expert Opinion, 2= Point Count, 3= Mist Netting, 4= Nest Searching,
5= Spot mapping, 6= Area Search, 7= Breeding Bird Atlas, 8= BBS Route, 9= Other/Local Opinion

Appendix 3. Coastal Cactus Wren Distribution-Orange County, CA. (modified from Harper and Salata 1991)

Locality
Site
Source
Year
Method 
Anaheim Peralta Hills Orange Co. BBA
1990
7
Anaheim  Gypsum Canyon McKernan
1991
1
Anaheim Hills Oak Canyon Nature Center Eggert
1996
2,4
Orange Co. Blind Canyon McKernan
1991
1
Caspers Regional Park Bell Canyon, San Juan Creek Rea and Weaver, Orange Co. BBA
1990
2,4, 7
Chino Hills Carbon Canyon Road Guthrie
1989
1
Chino Hills Carbon Canyon Guthrie
1989
1
Chino Hills Telegraph Canyon, Chino Hills State Park Guthrie, McKernan
1989, 1991
1
Cystal Cove State Park Cystal Cove Bluff Atwood 
1998
1,2,4
Dana Point Dana Point Headlands Orange Co. BBA, Roberts
1991
7
East Orange General Plan ** Willick
*
1
Eastern Transportation Corridor ** Willick
*
1
Costa Mesa Fairview Rock Willick
*
1
Fullerton ** Guthrie
1989
1
Fullerton Chevron Property Guthrie
1989
1
Fullerton (north) Coyote Hills Orange Co. BBA
1990
7
Orange Co. Gabino Canyon McKernan
1991
1
Irvine El Toro Marine Corps Air Station Gould
1991
1
Irvine Turtle Rock/Sand Canyon Reservoir Atwood 
1998
1
Irvine UC Irvine Ecological Reserve Atwood 
1998
1
Irvine San Joaquin Tranportation Corridor Roberts
1989
1
Irvine, San Joaquin Hills south of Sand Canyon Reservoir McKernan
1991
1
Irvine (east) east to Live Oak Canyon Orange Co. BBA
1990
7
Irvine Ranch ** Jone and Stokes Assc.
1993
2,6
Irvine Regional Park Irvine Regional Park Guthrie
1989
1
La Mirada (east) Coyote Hills Orange Co. BBA
1990
7
Laguna Beach Emerald Canyon, east to La Paz Road Orange Co. BBA
1990
7
Laguna Canyon Sycamore Hills Atwood 
1998
1,2,4
Laguna Hills ** Orange Co. BBA
1990
7
north Laguna Niguel ** McKernan
1991
1
Lake Forest ** Orange Co. BBA
1990
7
Lake Forest Foothill Ranch Roberts
1991
1
Lake Forest Serrano Creek Roberts
1991
1
Loma Ridge, Santa Ana Mts. between Irvine Regional Park/Modjeska Res. Orange Co. BBA
1990
7
Mission Viejo Oso Reservoir, south facing slope Roberts
1991
1
Mission Viejo Oso Reservoir, northwest facing slope Roberts
1991
1
Mission Viejo Naciente Ridge Roberts
1991
1
Mission Viejo English Canyon Stockwell
1991
1
Mission Viejo east to County Line Orange Co. BBA
1990
7
Mission Viejo southern portion Orange Co. BBA
1990
7
Mission Viejo/Lake Forest Upper Aliso Creek, El Toro Rd. Roberts
1991
1
Newport Beach Upper Newport Bay Ecological Reserve Atwood 
1998
1,2,4
North Laguna Laurel west of Laguna Canyon Road Atwood 
1998
1,2,4
Northern San Joaquin Hills northern section Willick
*
1
Orange Santiago Oaks Regional Park McKernan
1991
1
Pacific Coast Hwy between Laguna Beach/Newport Beach Guthrie
1989
1
Placentia (east) Chino Hills Orange Co. BBA
1990
7
Portola Hills Upper Aliso Creek, Santiago Canyon Rd. Roberts
1991
1
Rancho Mission Viejo San Juan Creek Rea and Weaver, Orange. Co BBA
1990
2,4,7
Rancho Mission Viejo San Mateo Creek, Cristianitos Canyon Rea and Weaver
1990
2,4
Rancho Santa Margarita
**
Orange Co. BBA
1990
7
Rancho Santa Margarita O'neill Regional Park Stockwell
1991
1
Rancho Santa Margarita/Trabuco Rattlesnake Canyon to Plano Trabuco McKernan
1991
1
San Clemente Segunda Deshada Canada Rea and Weaver
1990
2,4
San Joaquin Hills Laguna Canyon Roberts
1991
1
San Joaquin Hills Irvine Company Beedy
1991
1
San Joaquin Hills, Crystal Cove SP Los Trancos Canyon to Emerald Canyon McKernan
1991
1
San Juan Capistrano
**
Orange Co. BBA
1990
7
Starr Ranch Audubon Sanctuary Crow Canyon, s. side of Pruesker Peak McKernan, Rea and Weaver
1991, 1990
1,2,4
Tustin
**
Guthrie
1989
1
Tustin Peter's Canyon Willick
*
1
Tustin Shady Canyon Orange Co. BBA
1990
7
Yorba Linda Chino Hills, north of Featherly Regional Park McKernan
1991
1
Yorba Linda (north) Chino Hills McKernan
1991
1
** No specific site specified; 1= Expert Opinion, 2= Point Count, 3= Mist Netting, 4= Nest Searching,
5= Spot mapping, 6= Area Search, 7= Breeding Bird Atlas, 8= BBS Route, 9= Other/Local Opinion

Appendix 4. Coastal Cactus Wren Distribution-San Bernardino County, CA.
(modified from Harper and Salata 1991)

Locality
Site
Source
Year
Method 
Chino Hills  Chino Hills State Park Guthrie
1988-1989
1
Chino Hills Tonner Canyon, east of Diamond Bar McKernan
1991
1
Chino Hills Tonner Canyon, north of Arnold Reservoir McKernan
1991
1
Fontana
**
McKernan
1991
1
Loma Linda
**
McKernan
1991
1
Mentone
**
McKernan
1991
1
Rancho Cucamonga
**
McKernan, Guthrie
1991
1
Redlands
**
McKernan
1991
1
Rialto Lytle Creek Wash McKernan
1991
1
north of Redlands Airport Santa Ana River Wash McKernan
1991
1
** No specific site specified; 1= Expert Opinion, 2= Point Count, 3= Mist Netting, 4= Nest Searching,
5= Spot mapping, 6= Area Search, 7= Breeding Bird Atlas, 8= BBS Route, 9= Other/Local Opinion

Appendix 5. Coastal Cactus Wren Distribution-Riverside County, CA.
(modified from Harper and Salata 1991)

Locality
Site
Source
Year
Method 
Riverside Co. Arlington Mountatin McKernan
1991
1
Riverside Co. Bad Springs Creek McKernan
1991
1
Beaumont southwest McKernan
1991
1
Cajalco
**
McKernan
1991
1
Calimesa The Badlands, near Woodhouse Rd. McKernan
1991
1
Corona south McKernan
1991
1
Riverside Co. Dawson Canyon McKernan
1991
1
Riverside Co. Eagle Canyon McKernan
1991
1
Riverside Co. Hagador Canyon McKernan
1991
1
Riverside Co. Horsethief Canyon McKernan
1991
1
Riverside Co. Laborde Canyon McKernan
1991
1
Lake Mathews southern portion McKernan
1991
1
Lake Perris State Rec. Area Bernasconi Hills McKernan
1991
1
Riverside Co. Lakeview Mountains McKernan
1991
1
Riverside Co. Maybey Canyon McKernan
1991
1
Riverside Co. McBride Canyon McKernan
1991
1
Moreno Valley Box Springs Mountains McKernan
1991
1
Moreno Valley The Badlands, near Redlands Blvd. McKernan
1991
1
Moreno Valley/Lake Perris
**
McKernan
1991
1
Morongo Indian Reservation Potrero Creek McKernan
1991
1
Riverside Co. Motte Rimrock Reserve Carlson
1991
1
Riverside city limits McKernan, Carlson
1991
1
Riverside Co. Saddleback Flat McKernan
1991
1
San Jacinto
**
McKernan
1991
1
Murrieta Santa Rosa Plateau Carlson
1990
1
Temescal Wash south of Dawson Canyon McKernan
1991
1
** No specific site specified; 1= Expert Opinion, 2= Point Count, 3= Mist Netting, 4= Nest Searching,
5= Spot mapping, 6= Area Search, 7= Breeding Bird Atlas, 8= BBS Route, 9= Other/Local Opinion

Appendix 6. Coastal Cactus Wrens Distribution-San Diego County, CA.
(modified from Rea and Weaver 1990)

Locality
Site
Source
Year
Method 
Bonsall San Luis Rey River Rea and Weaver
1990
2, 4
Camp Pendleton San Mateo/San Onofre Creeks Rea and Weaver
1990
2, 4
Camp Pendleton unnamed creek, sw slope of Horno Hill Rea and Weaver
1990
2, 4
Camp Pendleton Aliso Creek Rea and Weaver
1990
2, 4
Camp Pendleton Santa Margarita River Rea and Weaver
1990
2, 4
Camp Pendleton Naval Weapons Station (Fallbrook Annex) Rea and Weaver
1990
2, 4
Camp Pendleton San Luis Rey River, Wire Mountain Rea and Weaver
1990
2, 4
Camp Pendleton San Luis Rey River, Windmill Canyon Rea and Weaver
1990
2, 4
Camp Pendleton San Luis Rey River, Pilgrim Creek Rea and Weaver
1990
2, 4
Camp Pendleton San Luis Rey River, Windmill Canyon Rea and Weaver
1990
2, 4
Camp Pendleton San Luis Rey River, Naval Weapons Sta. Rea and Weaver
1990
2, 4
Carlsbad Agua Hedionda Creek Rea and Weaver
1990
2, 4
Carlsbad San Marcos Creek Rea and Weaver
1990
2, 4
Chula Vista Sweetwater River Rea and Weaver
1990
2, 4
Dennery Canyon Otay River Rea and Weaver
1990
2, 4
El Cajon Los Penasquitos Creek Rea and Weaver
1990
2, 4
Encinitas Escondido Creek Rea and Weaver
1990
2, 4
Escondido San Dieguito River Rea and Weaver
1990
2, 4
Johnson Canyon Otay River Rea and Weaver
1990
2, 4
Lake Jennings County Park Los Penasquitos Creek Rea and Weaver, Eggert
1990, 1996
2, 4
Lakeside Los Penasquitos Creek Rea and Weaver
1990
2, 4
Lilac San Luis Rey River Rea and Weaver
1990
2, 4
Mission Hills Los Penasquitos Creek Rea and Weaver
1990
2, 4
Mother Miguel Mountain Sweetwater River Rea and Weaver
1990
2, 4
Otay Mesa Tijuana River Rea and Weaver
1990
2, 4
Paradise Hills Sweetwater River Rea and Weaver
1990
2, 4
Pauma Valley San Luis Rey River Rea and Weaver
1990
2, 4
Poway Los Penasquitos Creek Rea and Weaver
1990
2, 4
Proctor Valley Otay River Rea and Weaver
1990
2, 4
Ranch Bernardo San Dieguito River Rea and Weaver
1990
2, 4
Rancho Otay Otay River Rea and Weaver
1990
2, 4
Rancho Santa Fe San Dieguito River Rea and Weaver
1990
2, 4
San Diego Los Penasquitos Creek Rea and Weaver
1990
2, 4
San Pasqual Valley San Dieguito River Rea and Weaver
1990
2, 4
San Pasqual Valley San Pasqual SHP/SD Wild Animal Park Rea and Weaver
1990
2, 4
Santee Fanita Ranch, Los Penasquitos Creek Rea and Weaver
1990
2, 4
Spring Canyon Tijuana River Rea and Weaver
1990
2, 4
Spring Valley Los Penasquitos Creek Rea and Weaver
1990
2, 4
Sunnyside Sweetwater River Rea and Weaver
1990
2, 4
Sweetwater Reservoir Sweetwater River Rea and Weaver, Eggert
1990, 1996
2, 4
Valle de las Palmas Baja California Rea and Weaver
1990
2, 4
** No specific site specified; 1= Expert Opinion, 2= Point Count, 3= Mist Netting, 4= Nest Searching,
5= Spot mapping, 6= Area Search, 7= Breeding Bird Atlas, 8= BBS Route, 9= Other/Local Opinion