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A species endemic to the coastal and foothills regions of California, this bird suffers from habitat loss and fragmentation, and to a smaller extent, pesticide poisoning. Its ubiquitous singing and foraging antics have endeared it to nature lovers.
The California Thrasher is a striking songbird with a thick, long, decurved bill; dark iris; and dark eye-line. The 12-inch long bird has orange undertail coverts and buffy underparts. Sexes are alike.
An endemic of what is known as the California Biotic Province (mostly in the western part of the state), the thrasher breeds from sea level to the higher parts of the montane chaparral. It will breed in adjacent oak woodlands and pine-juniper scrub as well as occasionally in parks and gardens, but only if dense cover is available. Its dispersal is very limited.
In good habitat, the California Thrasher flourishes, but when habitat becomes degraded or fragmented, its numbers decline. Breeding Bird Survey Data from 1966 to 1994 show a small decrease in population; the downward trend (4.4 percent annually) is more prominent between the years 1980 and 1994. Declining California Thrasher count rates are consistent with losses in California Quail, Wrentits and related chaparral denizens, according to the San Francisco Bay Bird Observatory. See .http://www.sfbbo.org/miscpops.htm.
A mimic, the California Thrasher sings exuberantly year-round; its song has been likened to that of old world nightingales. The species forms pairs in winter. The female usually lays her clutch in February or March. Both sexes build the nest, hiding it well in dense vegetation. Incubation lasts 14 days; young fledge between 14 and 17 days. Both parents brood and feed by regurgitation for the first four days. They then feed young large insects, whose legs and wings have been removed.
The thrasher eats beetles, spiders, and other bugs year-round, and feasts on fruits when available. This ground-feeding bird will run for cover with its long tail raised.
The species does not adapt well to habitat fragmentation and modification. For example, it no longer breeds on the Monterey Peninsula probably because of development as well as the reduction of dense understory. The thrasher leaves disturbed areas even when remnant habitat patches remain. A smaller threat is the use of pesticides on citrus crops where the thrasher sometimes feeds.
Preserving intact habitat will be required to keep the population from declining further. Studies need to be conducted on whether predation increases when habitats become fragmented.
What Can You Do?
Audubon's Important Bird Area program is a vital tool for the conservation of California Thrasher as well as other species. To learn more about the Important Bird Area programs in California and how you can help, visit: http://www.audubon.org/bird/iba/
Follow Audubon At Home guidelines for a healthy yard and neighborhood to encourage habitat management that is beneficial to WatchList species. Visit: http://www.audubon.org/bird/at_home/index.html
Cody, Martin L. 1998. California Thrasher (Toxostoma redivivum). In The Birds of North America, No. 323 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.