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Avocet With its elegant profile and striking coloration, the American Avocet embodies a grace unique among North American birds. It is also remarkable for various aspects of its behavior, including varied feeding techniques, complex mating rituals and threat displays, and unusual patterns of intraspecific and interspecific brood parasitism and nest sharing. They breed in saline and freshwater wetlands throughout the western Great Plains, from Saskatchewan and Alberta south through Montana and the Dakotas to eastern New Mexico and the Texas Panhandle. They also breed in isolated wetland areas in the arid western states, including southern Idaho, northern Nevada and Utah (including the Great Salt Lake), central Arizona, eastern Washington, eastern Oregon, and northeast California. Many American Avocets winter in Mexico, along most of its coasts as well as some of its inland areas. They also winter along the Gulf Coast in Texas, Louisiana, and Florida, and along the Atlantic coast from south Florida as far north as Virginia. American Avocets in the Central Valley of California and the San Francisco Bay area are resident year-round, as are some populations in southern California, south Texas, and Mexico. American Avocet Range Map In the 1960s and 1970s, the species suffered population declines, largely from the loss of wetland habitat resulting from water diversion for human use. In addition, contamination of wetland habitat with selenium, which leaches from soil and accumulates through recycling of irrigation water, has been shown to lead to increased developmental abnormalities and mortality in American Avocets. Since 1995, owners of selenium-contaminated sites in northern California have been required to provide safe wetland habitat for American Avocets. Breeding success on the newly created sites has been much greater than initially expected, but long-term prospects for breeding at these sites are not clear. American Avocets feed in shallow water, while wading or swimming. They take a variety of aquatic invertebrates, locating food by sight and snapping it up, or sweeping their long bills through the water and capturing prey by touch. In definition of territories and in self-defense, American Avocets perform elaborate ritualized displays. One notable display, apparently related to the arrival of new breeding birds intending to nest in a given region, involves two pairs, or a pair and a third individual, facing each other in a circle and then stretching their bills toward each other. Upon the approach of a terrestrial predator, American Avocets may approach the predator with a teetering gait and outstretched wings, as if on a tightrope. They may also crouch on the ground as if incubating, only to move and crouch again in a new location. Nesting American Avocets aggressively attack predators, sometimes physically striking Northern Harriers or Common Ravens. They also may issue a series of call notes with gradually changing pitch, simulating the Doppler effect and thus making their approach seem faster than it actually is. Mating displays of American Avocets are equally remarkable. In its pre-copulation display, the male avocet preens himself with water, gradually gaining intensity to the point of frenzied splashing just before he mounts the female. After copulating, the pair intertwine their necks and run forward. Nesting is semicolonial, with greatest densities on islands, which are evidently preferred because of their isolation from terrestrial predators. American Avocets also nest on shorelines and dikes. Nests are scrapes in the ground, lined with grass or other vegetation, feathers, pebbles, or other small objects. Nests may also be completely unlined. Clutches generally contain four eggs. Each egg is pointed at one end, allowing the four eggs to fit neatly together in the nest, pointing together in the center. Eggs may also be laid singly in nests or on bare ground and left unincubated. The reasons for these single layings are not understood. Female American Avocets may lay one to four eggs in the nests of other females, who then incubate the eggs as if they were their own. Other species may also parasitize American Avocet nests. In two documented cases, American Avocets incubated their own eggs and Black-necked Stilt eggs together and reared the stilt hatchlings as if they were their own. American Avocets have also been observed incubating mixed clutches that include Common Tern eggs. Conversely, American Avocets may parasitize other species’ nests; single American Avocet eggs have been found in the nests of Mew Gulls. Young American Avocets stay in the nest no more than 24 hours after the last one in the brood hatches. They can walk and swim, and can even dive to escape predators. In denser colonies, young avocets may move between nests, to be cared for by adults who are not their genetic parents. American Avocets are tall, slim, long-legged shorebirds, measuring about 18 inches long, including their bill. Distinctive in plumage and morphology, they are not readily confused with any other North American shorebird. Breeding American Avocets have rusty orange heads and necks, with white around the eyes and at the base of the bill. Nonbreeding birds have pale whitish-gray heads and necks. In all plumages, wings and back are mostly black, with broad white marks on the shoulders and secondaries, creating a bold contrasting pattern visible in flight. Underparts are pure white; legs are pale blue-gray. Neck and legs are extended in flight. Bills are long, very thin, and curved upward. Females have slightly shorter bills with more pronounced curvature, on average. They also average slightly smaller overall than males. Otherwise, sexes are similar. American Avocets issue high-pitched, monosyllabic call notes, at intervals ranging from about half a second to about one full second. Visit Shaw
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