Golden-cheeked Warbler

Dendroica chrysoparia

Description

The golden-cheeked warbler is a small insectivorous songbird, about 5.5 in (14 cm) long. In breeding plumage, the male has bright yellow cheeks, outlined in black, and a black stripe running through the eye. The crown, throat, upperparts, and upper breast are black. The lower parts are white with black streaks along the sides. The female has yellowish olive upperparts, grayish wings and tail, and a duller yellow cheek patch.

Behavior

After wintering in Central America, the golden-cheeked warbler migrates north in early spring, arriving at its Texas breeding range in mid-March. Individuals return to the same nesting location year after year. Nests are located about 15 ft (4.5 m) from the ground in Ashe juniper (Juniperus ashei) trees. They are constructed of strips of Ashe juniper bark, bound together by cobwebs to form a small cup, which is then lined with feathers and fur. The female lays 3 to 5 creamy white eggs which she incubates for 12 days. Both male and female feed and care for the young, which fledge in about nine days, remaining nearby and forming a loose family group.

Golden-cheeked warblers feed on available insects or spiders, including caterpillars, green lace-wings, moths, small butterflies, katydids, walking-sticks, and small cicadas.

Habitat

The golden-cheeked warbler requires a mixed woods of mature Ashe juniper and various species of oak for nesting. It relies on Ashe juniper for nesting material and forages for insects in the oak canopies. The presence of Ashe juniper is an important habitat requirement, since even nests found in other types of trees are made of juniper bark. In addition, the junipers must be mature, since only trees over 20 years old shed their bark.

Distribution

The golden-cheeked warbler was discovered in Guatemala in 1859. It winters in Guatemala, Honduras, Nicaragua, Mexico, and possibly Belize. In spring the entire population migrates north to its breeding grounds which lie entirely within the state of Texas.

The breeding range of the golden-cheeked warbler is in central Texas, from Palo Pinto and Bosque counties, south through the eastern and south-central portions of the Edwards Plateau. One researcher has identified 31 counties in cental Texas as the nesting range of the species. In 1976, the total adult population was estimated at between 15,000 and 17,000 birds. Recent studies have found that the median population density was 15 pairs per 247 acres (100 hectares). The remaining suitable Ashe juniper/oak habitat has been only roughly estimated. At present it would have a carrying capacity of between 4,800 and 16,000 pairs.

Threats

The major threat to the golden-cheeked warbler is destruction of its breeding habitat for urban development and removal of junipers as a range management practice. As habitat areas are lost, remaining Ashe juniper/oak woods often become more fragmented, putting the golden-cheeked warbler at greater risk from predators and nest parasitism by brown-headed cowbirds.

During the late 1940s a juniper eradication program (including Ashe juniper) was begun in Texas in order to clear land for pasture improvement and urbanization. By 1970 about 50% of juniper acreage had been cleared.

Over the last two decades destruction of Ashe juniper/oak habitat has continued, particularly in expanding urban areas. A 1990 study indicated that over the last ten years sample areas suffered losses of warbler habitat ranging from 15 to 45%. Western Travis County, immediately west of Austin, and the Austin-San Antonio corridor experienced yearly losses of habitat of about 4%. In the northern portion of the breeding range, 15% of available habitat was lost over an eight year interval. In rural areas habitat loss has been holding steady at about 2% a year for the last 20 years. At the estimated rate of loss, however, the carrying capacity of the habitat was reduced by more than 50% by 2000.

When areas of golden-cheeked warbler habitat are lost, adjacent areas become more fragmented. This results in an increase in the amount of "edge" habitat, in turn allowing predators, such as scrub jays, grackles, feral cats, and rat snakes, easier access to warbler nests. Increased edge also leads to more brood parasitism by brown-headed cowbirds, which lay their own eggs in the nests of smaller birds. The larger cowbird chicks are raised by the foster parents and out-compete the smaller chicks for food.

Conservation and Recovery

The loss of habitat of the golden-cheeked warbler was occurring so rapidly in the urban areas around Austin that the U.S. Fish and Wildlife Service (FWS) used its power to list the species as Endangered on an emergency basis. The FWS hoped that this action would allow time for the development of a conservation plan for the Austin region that would protect the golden-cheeked warbler and other endangered species in the area, including the black-capped vireo (Vireo atricapilla ) and five rare cave species. In 1992, the FWS approved a Recovery Plan for the golden-cheeked warbler, and a Recovery Team was appointed. One of the cornerstones of the program is the establishment of the Balcones Canyonlands National Wildlife Refuge, which began with the purchase of 3,500 acres (1,400 hectares) containing habitat of the rare warbler. Various proposed developments have also been reviewed for their potential impacts on the golden-cheeked warbler, to ensure its critical habitat was not places at risk. In addition, Travis County, the city of Austin, The Nature Conservancy, the Texas Parks and Wildlife Department, National Audubon Society, FWS, and other groups are cooperating on a comprehensive Habitat Conservation Plan for seven listed species in the Austin region, including the golden-cheeked warbler. The Nature Conservancy, for example, is developing the Hill Country Biore-serve, which will preserve much of the critical habitat on private land. Also, the FWS is working with the Texas Parks and Wildlife Department, Soil Conservation Service, and other organizations to formulate Golden-cheeked Warbler Conservation Management Guidelines for private landowners. Additional recovery actions include increased landowner education and involvement, identification of winter and migratory habitat, reduction in nest parasitism from cowbirds, and protection of all habitat types (e.g., nesting, wintering) required to recover the golden-cheeked warbler.

Contact

U.S. Fish and Wildlife Service
Division of Endangered Species and Habitat Conservation
2105 Osuna Road N.E.
Albuquerque, New Mexico 87113-1001
Telephone: (505) 346-2525
E-mail: r2esweb@fes.gov
http://ifw2es.fws.gov/

References

Kroll, J. C. 1980. "Habitat Requirements of the Golden-cheeked Warbler: Management Implications." Journal of Range Management 33:60-65.

Pease, C. M. and L. G. Gingerich. 1989. "Habitat Requirements of the Black-capped Vireo and Golden-cheeked Warbler Populations Near Austin, Texas." Report Prepared for Austin Regional Habitat Conservation Plan, Biological Advisory Team, Austin, Texas.

Pulich, W. M. 1976. "The Golden-cheeked Warbler, a Bioecological Study." Texas Parks and Wildlife Department, Austin.

U.S. Fish and Wildlife Service. 1992. Status of Listed Species and Recovery Plan Development. Golden-cheeked Warbler. http://www.npwrc.usgs.gov/resource/distr/others/recoprog/states/species/dendchry.html

Wahl, R., D. D. Diamond, and D. Shaw. 1990. "The Golden-cheeked Warbler: a Status Review." U.S. Fish and Wildlife Service, Fort Worth, Texas.