Solek, C. and L. Szijj. 2004. Cactus Wren (Campylorhynchus brunneicapillus). In The Coastal Scrub and Chaparral Bird Conservation Plan: a strategy for protecting and managing coastal scrub and chaparral habitats and associated birds in California. California Partners in Flight. http://www.prbo.org/calpif/htmldocs/scrub.html

SHORTCUTS

range map

action plan summary

references

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 an 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).

DISTRIBUTION:

HISTORICAL DISTRIBUTION 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.

CURRENT BREEDING DISTRIBUTION:

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).

WINTER 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.

ECOLOGY:

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.

TIME AND OCCURENCE OF SEASONAL MOVEMENTS:

C. brunneicapillus is resident throughout its range in California and does not migrate or make long distance seasonal movements.

FOOD HABITS:

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).

DIET:

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.) and fiddleneck (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.

DRINKING:

No data exists on free water consumption in California populations, but the species 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.

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)

Areas supporting Coastal Sage Scrub are dry, generally receiving 14 inches 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.

NEST 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 (Rea and Weaver 1990).

HEIGHT OF NEST:

Averaging 1 m (3 ft.) above ground level.

HEIGHT OF PLANT:

Averaging 1.2-1.5 m ( 4-5 ft).

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.

VEGETATION SURROUNDING THE NEST:

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).

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.

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).

DOMINANT SHRUB SPECIES:

California buckwheat, Eriogonum fasiculatum, California sagebrush, Artemesia californica, prickly pear and coastal cholla Opuntia sp.; California encelia, Encelia californica.

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.

DOMINANT FORB SPECIES:

Mimulus sp., herbaceous annuals

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.

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.

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.) .

SNAGS:

Individuals have been observed using snags, fence posts and fence lines for calling and display.

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).

BREEDING BIOLOGY:

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).

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).

CLUTCH SIZE:

3-5 eggs

INCUBATING SEX:

Female

INCUBATION PERIOD:

16 days

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).

NESTLING PERIOD:

19-23 days

PARENTAL CARE:

Both sexes tend the young.

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.

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.

LANDSCAPE FEATURES:

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).

FRAGMENTATION:

This is a concern for the coastal populations of C. brunneicapillus in California, but empirical data on the effects of this fragmentation are limited. Most coastal populations are now isolated due to urbanization of the region and persist in highly 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 may have difficulty in crossing urbanized areas to re-populate remnant parcels of suitable habitat. Population viability analyses suggest that the small size of these subpopulations coupled with habitat fragmentation may constrain the long-term viability of the metapopulation (Ogden Environmental and Energy Services 1992). Geographic isolation of coastal and interior populations has also been enhanced by urbanization, and may be facilitating genetic differentiation among these segments of the population (Rea and Weaver 1990, Eggert 1996).

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 et al. (1995) found that Cactus Wrens may have difficulty recolonizing burned areas 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 military activities have also contributed to habitat destruction, especially in and around Camp Pendleton Marine Corps Base, San Diego County (Rea and Weaver 1990, Harper and Salata 1991). Degradation of Cactus Wren habitat due to city/county weed abatement projects, legal and illegal grading/clearing activities, and recreational activities has been documented (Harper and Salata 1991).

ADJACENT LAND USE:

Suburban development, agriculture and grazing

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 nestlings handled without abandonment by adults. Destruction of coastal sage scrub tends to eliminate the Cactus Wren from an area, with most populations unable to adapt to most suburban conditions (Guthrie 1974).

PESTICIDE USE:

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

PREDATORS:

Cooper’s Hawk (Accipter cooperii), American Kestrel (Falcosparverius), Greater Roadrunner (Geococcyx californianus), snakes, woodrats. Aggressive interactions with Western Scrub Jays( Aphelocoma coerulescens) and Northern Mockingbirds (Mimus polyglottus) have been observed.

EXOTIC SPECIES INVASION/ENCROACHMENT:

Feral cats, rats

DEMOGRAPHY AND POPULATION TRENDS:

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.).

PRODUCTIVITY MEASURE(S):

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).

SURVIVORSHIP:

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 9.1 percent (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 life following 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 be 48.5 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 survival rate 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.

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).

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.).

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:

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.

ACTION PLAN SUMMARY

SPECIES: Coastal Cactus Wren (Campylorhynchus brunneicapillus)

STATUS:

A coastal population from San Diego County was nominated for subspecies status as C. b. sandiegensis in 1990 and subsequently proposed for Federal Threatened status in 1991. Since this suspecies designation was not recognized by the American Ornithologists' Union Committee on Classification and Nomenclature, the San Diego population was declined for Federal Threatened listing by the U.S. Fish and Wildlife Service 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 California is 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:

1. Identify all localities with breeding populations by initiating population surveys by county, with particular emphasis on counties where population status is unclear(e.g. Ventura County).

2. Increase the number of protected areas of coastal sage scrub habitat with populations of Cactus Wrens through land acquisitions on a state and local level. Create habitat buffers around existing protected areas, if feasible.

3. Promote scientific studies of reproductive success, survivorship, and dispersal capacity in the species. Identify on-going research on coastal Cactus Wren ecology, improve communication among the principal investigators, and coordinate research efforts whenever possible.

4. Explore the efficacy of habitat restoration and promote sound urban habitat conservation practices (e.g., discourage cactus removal by homeowners at the urban/rural interface and modify current city/county weed abatement and fire suppression programs to limit the unnecessary destruction of cactus and coastal sage scrub habitats).

REFERENCES:

American Ornithologists’ Union. 1998. Checklist of North American Birds. 7^th 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.

Benson, L. 1969. The native cacti of California. Stanford University Press, Stanford, CA. 243 pp.

Bent, A.C. 1948. Life histories of North American nuthatches, wrens, thrashers, and their allies. U.S. Nat. Mus. Bull No. 195.

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. In Brushfires in California wildlands: ecology and resource management (J.E. Keeley and T. Scott, Eds.). International Association of Wildland Fire, Fairfield, WA.

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

Dawson, W.L. 1923. The birds of California. Vol. 1. South Moulton Company, San Diego.

Department of the Interior, U.S. Fish and Wildlife Service. 1994. One year finding for a petition to list the Pacific coast population of the cactus wren under the Endangered Species Act. 50 CFR Part 17 (FR Doc 94-21785, filed 9-2-94).

DeSimone, S. 1995. California’s Coastal Sage Scrub. Fremontia 23: 3-8.

Dudek and Associates. 2000.Species Account: Cactus Wren from Understanding the Plants and Animals of the Western Riverside MSHCP.

Eggert, L.S. 1996. A phylogeographic approach to management of coastal California Cactus Wrens (Campylorhynchus brunneicapillus). M.S. thesis, San Diego State University, San Diego. 63 p.

Environmental Planning, The Irvine Company. 1993. Field study methods for conducting surveys of California gnatcatchers (Polioptilia californica), cactus wrens (Campylorhynchus brunneicapillus), and other special-status species at the Irvine Ranch, Orange County, California. August. Newport Beach, CA. Prepared by Jones and Stokes Associates, Inc. (JSA 93-129). Sacramento, CA.

Facemire, C.F., M.E. Facemire, and M.C. Facmire. 1990. Wind as a factor in the orientation of entrances of Cactus Wren nests. Condor 92:1073-1075.

Farley, G.H. and J.N. Stuart. 1994. Atypical nesting sites of the Cactus Wren. Tex. J. Sci. 46: 193-195.

Freeman, L.C. 1994. The role of coordinated male and female displays and duetting

in the territorial behavior of Northern Cactus Wrens (Campylorhynchus brunneicapillus).

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

Gallager, S.R. 1997. Atlas of breeding birds, Orange County, CA. Sea and Sage Audubon Press.

Garret, K., and J. Dunn. 1981. Birds of southern California-status and distribution. Western Tanager (Los Angeles Audubon Society): 291-292, 397.

Garrett, K.L. 1991. The status of the Cactus Wren, Campylorhynchus brunneicapillus, in Los Angeles County, California. Prepared for U.S. Fish and Wildlife Service.

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

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

Grinnel, J. and A. Miller. 1944. The Distribution of the Birds of California. Pacific Coast Avifauna 27: 337-338.

Guthrie, D.A. 1974. Suburban bird populations in southern California. Am. Midl. Nat. 92 (2): 461-466.

Harper, B. and L. Salata. 1991. A status review of the coastal Cactus Wren. U.S. Fish and Wildlife Service, Southern California Field Station, Laguna Niguel, California.

Harrison, C. 1978. A field guide to the nests, eggs, and nestlings of North American birds. Collins Publishers.

Hensley, M.M. 1959. Notes on the nesting of selected species of birds in the Sonoran Desert. Wilson Bulletin 71: 86-92.

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

Northern Cactus Wrens (Campylorhynchus brunneicapillus couesi Sharpe).

M.S. thesis, Arizona State University.

Marr, T.G. 1981. Breeding and foraging ecology of the Cactus Wren in a variable environment. Ph.D. dissertation, New Mexico State University, Las Cruces.

Marr, T.G. and R.J. Raitt. 1983. Annual variations in patterns of reproduction of the Cactus Wren (Campylorhynchus brunneicapillus). Southwest Nat. 28: 149-156.

Mearns, E.A. 1902. The Cactus Wrens of the United States. Auk 19: 141-145.

McGee, M. 1985. Interspecific nest interference: the influence of Cactus Wrens (Campylorhynchus brunneicapillus) on Verdin (Auriparus flaviceps) nest site selection. M.S. thesis, University of Arizona, Tucson.

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.

Milton, S.J., W.R.J. Dean, G.I.H. Kerley, M.T. Hoffman, and W.G. Whitford. Dispersal of seeds as nest material by the cactus wren. Southwestern Nat. 43 (4): 449-452.

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.

O’Leary. J.F. 1995. Coastal Sage Scrub: Threats and current status. Fremontia 23: 27-31.

Parker, K.C. 1986. Trunk vs. ground feeding in CactusWrens (Campylorhynchus brunneicapillus, Troglodytidae). Southwest Nat. 31: 111-114.

Pyle, P., S. Howell, R. Yunick, D. DeSante. 1987. Identification guide to North American Passerines. Slate Creek Press, Bolinas, California.

Rea, A.M. 1986. Geographic variation (of Campylorhynchus brunneicapillum): (1) NW, peninsular, and insular races, (2) N and E (mainland) races. Pages 118-120 In A.R. Phillips, editor. The known birds Middle and North America, Part I. Denver, Colorado.

Rea, , A. M. and K. Weaver. 1990 The taxonomy, distribution, and status of coastal California Cactus Wrens. Western Birds 21: 81-126.

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.

Ricklefs, R.E. 1975. Patterns of growth in birds. III. Growth and development of the Cactus Wren. Condor 77: 34-45.

Ryden, V.M.J. 1981. Repertoire size and singing "style" in the Cactus Wren. M.S. thesis, California State Polytechnic University, Pomona.

Sauer, J.R., J.E. Hines, G. Gough, I. Thomas, and B.G. Peterjohn. 1997. The North American Breeding Bird Survey Results and Analysis. Version 96.4. Patuxent Wildlife research Center, Laurel, MD.

Selander, R.K. 1964. Speciation in the wrens of the genus Campylorhynchus. University

of California Press, Berkeley and Los Angeles, CA.

Short, H.L. 1985. Habitat suitability index models: Cactus Wren U.S. Department of the Interior, Fish and Wildlife Service Biological Report 82, Washington D.C.

Simons, L.S. 1988. Experimental studies in the reproductive ecology of Cactus

Wrens. Ph.D. dissertation, Arizona State University.

Simons, L.S. and T.E. Martin. 1990. Food limitation of avian reproduction: an experiment with the Cactus Wren. Ecology 71: 869-876.

Simons, L.S. and L.H Simons. 1990. Experimental studies of nest destroying behavior by cactus wrens. Condor 92: 855-860.

Skutch, A.F. 1935. Helpers at the nest. Auk 52: 257-273.

Smith, E.L. 1970. Cactus Wrens attack Ground Squirrel. Condor 72: 363-364.

Soule, M.E., Bolger, D.T., Alberts, A.C., Wright, J., Sorice, M., and Hill, S. 1988. Reconstructed dynamics of rapid extinctions of chaparral requiring birds in urban habitat islands. Conserv. Biol. 2: 75-92.

Steinitz et al. 1997. Biodiversity and Landscape Planning: An Alternative Future for the Region of Camp Pendleton, California. Alexander and Victoria Wiley Professor of Landscape Architecture and Planning. Harvard University, Graduate School of Design, Cambridge, MA.

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

Storer, T.L. 1920. Lizard eaten by Cactus Wren. Field and Study. Condor 22: 159.

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

Tutton, J., B. Harper, and R. Zembal. 1991. A survey of the California gnatcatcher and Cactus Wren on Camp Pendleton, San Diego County, California (Final). Prepared for the U.S. Marine Corps Environmental and Resource Management Office, Camp Pendleton, CA. by the USFWS Southern California Field Station, Laguna Niguel Office, 25 p.

Unitt, P. 1984. The Birds of San Diego County. San Diego Society of Natural History Memoir 13. 276 pp.

Weaver, K.L. 1982. Breeding bird populations of coastal sage scrub communities in southwestern California. Am. Birds 36: 93-94.

Wheeler, T.R. 1997. Habitat requirements of the coastal Cactus Wren, Campylorhynchus brunneicapillus, in eastern Los Angeles County. Senior Thesis in Biology, Joint Science Department of the Claremont Colleges.

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

Wolford, M.J. 1969. Vocal repertoire of the Cactus Wren (Campylorhynchus brunneicapillus). M.S. thesis, University of Arizona, Tuscon.

Zimmerman, D.A. 1957. Some remarks on the behavior of the Yucatan cactus wren. Condor 59: 53-58.

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

* 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)

** 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)

** 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).

** 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)

** 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).