Introduction

Despite its restricted breeding range, the Western Sandpiper is one of the commonest shorebirds of the Western Hemisphere, wintering along the Pacific coast of North America and the south Atlantic coast. In migration, this species stages in huge, spectacular flocks, particularly along the Pacific coast from San Francisco Bay to the Copper River Delta in Alaska. Estimates suggest that as many as 6,500,000 individuals pass through the Copper River Delta during just a few weeks each spring. Most Western Sandpipers migrate along the Pacific coast, although significant numbers move through interior North America. Relatively little is known of the biology of wintering birds, particularly those in the southeastern United States, the West Indies, Central America, and South America.

Most information on the reproductive biology of this species derives from a four-year study on the Yukon-Kuskokwim Delta in Alaska (Holmes 1971, 1972, 1973), although major gaps in information remain. Males provide a nest scrape to hold the typical four-egg clutch. Both members of the pair incubate eggs and tend young until they fly. This species eats a varied diet, although insect larvae comprise the majority of its food on the breeding grounds. Along coastal areas during migration, various species of crustaceans and polychaete worms make up the bulk of the diet. Still lacking for this species are basic data on reproductive success and survivorship.