Le Conte's Thrasher

Toxostoma lecontei

John Cassady
  • MIMIDAE
  • Mimids
  • 190,000

An uncommon permanent resident in the deserts of southwestern United States and northwestern Mexico, the Le Conte's Thrasher is a secretive, difficult-to-find bird. It is sensitive to disturbance, including off-road vehicle use, livestock grazing, oil drilling and development. The Le Conte's Thrasher is designated as a species of special concern by the California Department of Fish and Game, and the U.S. Fish and Wildlife Service has considered listing it as federally threatened or endangered.

Identification
Sexes are alike. This sandy-colored, 10-inch long bird blends well with dry desert vegetation. Its black tail contrasts with its gray, unspotted breast and belly. This secretive bird sports a long, decurved bill and dark eyes. Le Conte's is paler overall and lacks the pale supercilium and dark cheeks of the California Thrasher.

Distribution and Population Trends
Le Conte's Thrasher is a widespread, but rare permanent resident in the western and southern San Joaquin Valley, upper Kern River Basin, Owens Valley, Mojave Desert, and Colorado Desert in southwestern United States. Five pairs or fewer are found even in optimum habitat per square mile, an extremely low density compared with other songbird species. California serves as a main population center for this species - even here populations have declined, especially in the San Joaquin Valley. Numbers are also declining in Arizona. Satellite imagery shows that 26 percent of the historical breeding areas for Le Conte's Thrasher no longer have suitable habitat for this species.

Ecology
Earliest nesting for this nonmigratory species begins in February in California and later northward until about the end of May, peaking in mid-March through April. It prefers breeding in saltbush/shadscale vegetation or cholla cacti in sandy substrate. It needs vegetative litter for cover and for obtaining prey.

The cup-like nest is built low to the ground in a dense shrub. Incubation lasts 14 to 20 days; young fledge 12 to 15 days after hatching. Double broods are common.

The Le Conte's Thrasher runs quickly with its dark tail cocked. It digs small pits in the ground with its long bill, searching for seeds, insects, and small vertebrates in the litter; it will also take small bird eggs. Interestingly, this species seems not to need water, since it lives where surface water is rarely available. Scattered desert shrubs and cactus are necessary for cover, especially at night or in the hot afternoon sun.

Threats
This bird lives in some of the most inhospitable regions of the desert; yet, at least in California, most of its habitat is being used by off-road vehicle enthusiasts. Its wariness of human beings makes it particularly susceptible to, for example, motorcycles racing through a desert wash near where it nests in large shrubs. Agricultural and urban development as well as oil extraction also threaten this species.

The Le Conte's Thrasher is also susceptible to DDT contamination, and its numbers may have declined before the pesticide was banned in the 1970s.

Conservation
The U.S. Bureau of Land management and National Park Service have set aside conservation regions in the San Joaquin Valley in California, which could afford some protection of this species. In 1980, the Bureau of Land Management, U.S. Department of Interior, designated the Desert Tortoise Research Natural Area in California as an area of critical environmental concern. This 39.5-square-mile region contains prime natural habitat for desert tortoises. The habitat also attracts Le Conte's Thrasher, which breed here. Stopping off-road vehicle activity where these birds breed should also help.

What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of Le Conte's Thrasher as well as other species. To learn more about the Important Bird Area programs and how you can help, visit: http://www.audubon.org/bird/iba/

Support decisions limiting off-road vehicle activity where this bird breeds and write letters to the National Park Service encouraging the protection of this bird's habitat.

Californians may consider contributing to the tax check-off program for threatened and endangered species, which also protects rare species and those of special concern.

References
California Department of Fish and Game Habitat Conservation Planning Branch. 1983. California's Plants and Animals, Le Conte's Thrasher. http://www.dfg.ca.gov/whdab/B400.html

Sheppard, J. M. Le Conte's Thrasher (Toxostoma lecontei). In The Birds of North America, No. 230 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.