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