The spring migration of shorebirds at Willapa Bay, Washington, USA, in 1983

This study documents the distribution and abundance of shorebirds at Willapa Bay, Washington, a major estuary on the Pacific Coast of the United States, during spring (northbound) migration in 1983. We also noted general patterns of habitat use and movements by shorebirds. Our primary focus was on the northern and eastern portions of the bay, with less frequent counts in the southern and western portions. Counts were carried out on 33 days on a variable set of up to 16 survey sites for a total of 202 count days. We documented 24 species, with the most abundant being Western Sandpiper Calidris mauri, Dunlin C. alpina, Short-billed Dowitcher Limnodromus griseus, Red Knot C. canutus, Black-bellied Plover Pluvialis squatarola, and Semipalmated Plover Charadrius semipalmatus. Total numbers peaked on 23–24 April, coincident with the peak counts of Western Sandpipers and Short-billed Dowitchers. Each species displayed a unique phenological pattern of abundance that we compared to other local studies. In terms of relative abundance at our 16 survey sites, the mouth of the Willapa River (two nearby sites on the north and south sides) and Porter Point (near the mouth of the Bear River) had the highest overall numbers (30% and 17% of the total counted at the peak, respectively). Leadbetter Point and Tokeland had the highest species richness, both overall (16–17 species) and on a daily basis (daily mean = 11–12 species). On 23 April, we estimated a total of over 125,000 shorebirds at 11 sites, and over 114,000 at a slightly different set of 12 sites on 24 April. We know that these counts did not account for all birds in the estuary because we did not count at all sites on any one day and we were unable to access some sites. The numbers of Red Knots, a species of conservation concern, exceeded previous and more recent counts for the species at Willapa Bay. Our data confirm the continental significance of Willapa Bay for migrant shorebirds and its status as a site in the Western Hemisphere Shorebird Reserve Network, as well as offering a historical indication of shorebird abundance in the early 1980’s.