Western Sandpiper (Calidris mauri)
Western Sandpipers spend a lot of their life migrating. Unlike other birds, they migrate most of the year, flying an average of 180 to 200 miles a day. Their main breeding area is in the Yukon, where they lay their eggs in mid-May. By the end of June, the eggs have hatched and they start flying south. Some fly as far as South America using the Pacific Flyway. The Western Sandpiper is a shore bird and can be seen in the Bay Area during the winter months.
(Source: The Sibley Guide to Birds, David Allen Sibley, Knopf, 2000, Cornell Lab of Ornithology)