The American Avocet is a large, striking shorebird with long bluish legs, a long recurved bill, and a black-and-white chevron pattern on its back. The only avocet in the world with an annual color change, its head and neck become cinnamon in early spring as birds begin to form pairs and migrate to breeding areas. Its melodic alarm calls are a characteristic feature of the shallow alkaline wetlands where it breeds in semicolonial groups. Avocet parents are noted for their complicated suite of deceptive and aggressive antipredator behaviors, and sometimes appear comical as they respond to the presence of a potential predator near their nests. The long recurved bill, used for both visual and tactile feeding on invertebrates, is so sensitive that a bird in the hand will recoil at the gentlest touch.
American Avocets specialize in using the temporally unpredictable wetlands of the arid western United States and breed in large numbers at the marshes of Great Salt Lake, the Tulare Basin of California, and in shifting abundance across the northern Great Basin. In spite of such flexibility, this species has not escaped the effects of humans. In the arid west, wetlands compete directly with urban and agricultural areas for limited supplies of fresh water. Some wetlands that were once important avocet breeding centers have now declined in area by as much as 90%. Embryo deformities and decreased hatchability have been associated with selenium contamination in irrigation drain water.
The species was extirpated from much of its eastern range at the beginning of the twentieth century. Its persistence in western North America will depend on inland wetland conservation and restoration efforts.
Research on American Avocets has focused on behavior and population ecology. Robert B. Hamilton (1975) described and compared the behaviors of American Avocets and Black-necked Stilts (Himantopus mexicanus) in California, and Flash Gibson (1971, 1978) recorded breeding-season time budgets from Oregon. The conspicuous antipredator behaviors were studied in depth by Tex A. Sordahl (1980, 1981, 1982, 1984, 1986, 1988, 1990, 1994, in press) in Utah. Winter behavior and habitat use was a focus of research by Ruth Boettcher (1994, Boettcher et al. 1994, 1995) in South Carolina and by Thomas J. Evans (1988, Evans and Harris 1994) in California. American Avocets and Black-necked Stilts have also been a primary focus of ecotoxicological studies on the effects of irrigation drain water on breeding waterbirds (e.g., studies by H. M. Ohlendorf, Joseph P. Skorupa, and unpublished work of C. Marn). Most recently, Julie A. Robinson and Lewis W. Oring (Robinson 1996, Robinson and Oring 1996, in press) conducted population studies of hundreds of marked individuals in California, Nevada, and Utah, providing data on migratory movements, natal and breeding dispersal, population regulation, and population spatial structure.
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