Courtesy Kenn Kaufman
The Western Sandpiper breeds almost entirely around the western coast of Alaska. The breeding range begins just north of the Alaska Peninsula, and extends all the way up the western coast to Barrow. A small Siberian population also exists on the eastern edge of the Chukotskiy Peninsula. In winter, the species disperses far and wide. Western Sandpipers can be found as far away as the northeastern coast of South America, and as far north along the Atlantic coast as New Jersey. The largest concentrations of wintering birds occur in Mexico and Central America.
In winter, spring, and fall, this species can be found on shorelines, beaches, or within tidal estuaries. While it is generally a coastal bird, it can also be found far inland during migration, usually on mudflats or in flooded fields. In summer, Western Sandpiper inhabits the Alaskan tundra, where it nests in dry, grassy areas near low marshes, ponds or lakes.
Western Sandpiper feeds by walking over muddy areas or wading in shallow water, probing the mud constantly in search of prey items. In dry areas, food can also be located visually. Its diet is varied; common prey includes flies, beetles and other insects, as well as worms, small crustaceans, mollusks, and even seeds.
Males arrive on the breeding grounds earlier than the females. Each male establishes a territory, which is advertised to arriving females with the performance of frequent display flights. Prior to the arrival of the females, he excavates several nest scrapes within his territory. Once he has attracted a mate, she chooses the scrape that suits her best, and nesting begins. Materials such as lichen or leaves are added to the nest, and three or four cream colored, streaked eggs are laid. Both parents share incubation duties, and the eggs hatch within about three weeks. Western Sandpiper chicks leave the nest within 24 hours of hatching, and are capable of feeding themselves almost immediately. One or both parents accompany the chicks until they learn to fly, but males are more likely to remain with the chicks than are females. Chicks take flight within three to four weeks, at which point they are deserted by the remaining parent(s). Immature birds form flocks on the breeding grounds, then embark on their first southerly migration together by the end of August.
During migration, Western Sandpipers tend to move in flocks separated by gender. In spring, males arrive first at the breeding grounds. In fall, females often leave their mate and chicks soon after hatching to form flocks with other females. Males tend to winter further north than females. The northbound migration of Western Sandpipers can be truly fantastic, with hundreds of thousands to millions of birds arriving nearly simultaneously at certain migratory staging areas. The Western Sandpiper makes its way up and down the coast in spring and fall, respectively, via a series of short flights from one stopover point to the next. The route seems to be specifically timed; banded adults have been recovered arriving at a Central American site on exactly the same date from year to year. While the migratory route is generally coastal, the species is also known to migrate over land, specifically between the southern Atlantic and Gulf coasts of North America and the Pacific Northwest.