| Summary: | In this study, I examined shorebird use of agricultural fields during migration and winter, between September 1988 and April 1989. I compared field use with use of adjacent mudflats and salt marsh over the tidal cycle for ten species of shorebirds: Killdeer (Charadius vociferus), Common Snipe (Gallinago gallinago), Western Sandpiper (Calidris mauri), Least Sandpiper (Calidris minutilla), Dunlin (Calidris alpina), Marbled Godwit (Limosa fedoa), Long-billed Curlew (Numenius americanus), Willet (Catoptrophorus semipalmatus), Black-bellied Plover (Pluvialis squatarola), and Greater Yellowlegs (Tringa melanoleuca). Killdeers and Common Snipe were field specialists, and did not use the other habitats in significant numbers (greater than zero) in any season. After the seasonal rains began in late fall, several other species started to use the fields. Dunlins, Least Sandpipers, Long-billed Curlews and Marbled Godwits were field opportunists, and used the fields only during intermediate and high tides. Black-bellied Plovers and Greater Yellowlegs were seasonal field generalists, and used fields during all tides in the two wettest seasons. Only two species did not use fields in significant numbers. Western Sandpipers were mudflat specialists. Willets were salt marsh opportunists in that they mainly used mudflats, but shifted to salt marsh at high tide. Short vegetation and the presence or absence of standing water in the fields were the two most important field characteristics influencing field use by shorebirds. More than half the birds present in fields were foraging, except Common Snipe and Long-billed Curlews. Field opportunists (Least Sandpipers, Dunlins, and Marbled Godwits) foraged at faster rates on mudflats than on fields. The seasonal generalist (Black-bellied Plover) foraged equally fast and used pecking for foraging in both habitats. Thesis (M.S.)--Humboldt State University, Natural Resources, Wildlife Management, 1993
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