Shorebirds and Benthic Fauna of Tidal Mudflats in Estero de Punta Banda, Baja California, Mexico

We studied habitat use by shorebirds as related to tide and benthic invertebrates on three mudflats at Estero de Punta Banda, Baja California, Mexico, between January and April, 2000. We recorded 15 shorebird species and 7974 individuals. The most abundant birds were marbled godwits (Limosa fedoa), small sandpipers (Calidris alpina, C. mauri, and C. minutilld), and willets (Catoptrophorus semipalmatus). The three sites were different in their shorebird assemblages, and shorebird density was significantly greater on the site closest to the mouth of the estuary. The benthic fauna in our samples included 14 polychaete and 1 cumacean families; 8 bivalve species, 7 gastro- pod species, 7 amphipod species, 4 decapod species, and 1 species of isopod. Benthic invertebrate abundance was significantly greater at the site closest to the mouth of the estuary in winter, and at the central site in spring. Abundance of shorebirds was clearly inverse to tide height. Shallow and deep probers responded differently to the tide cycle at two sites. The most used feeding microhabitat, among four studied, was the waterline, although benthic inver- tebrate abundance was not different among habitats. The benthic fauna in our samples was potential food for the shorebirds present