The Estero de Punta Banda, B.C., Mexico as a link in the "Pacific Flyway": Abundance of shorebirds

Thirteen shorebird species and 5683 individuals were recorded at Estero Punta Banda from October 1988 to April 1989 in three soft-bottom habitats bordering the northern tip of the sand bar (open beach; terminal beach; mud-flats) and a semi-protected seasonal pond at the southwest comer of the estuary. The open beach (seven species; 1310 individuals), mud-flats (13 species; 3958 individuals) and the pond (two species; 146 individuals) harbored distinctive species assemblages while the terminal beach (five species; 239 individuals) acted as an extension of the open beach and mud flats. Most species where exclusive of a single habitat, or almost exclusive (species that occur in more that one habitat but exhibit strong quantitative differences among them). Seasonal changes were rather neat, although the study period missed the first part of the autumn migration towards the south. Seasonal movements were not synchronic in the different habitats. We estimated that about 14,000 shorebirds visit the lagoon each season (3,000 in the open beach; 11,000 in mud-flats). Although most species had been recorded for the site, quantitative data and evidence of the role of estero Punta Banda along the Pacific Flyway are offered in this study for the first time. Distinctive species assemblages in the different habitats, and asynchronism of migration in each, show that patchiness of habitats is important for the maintenance of species richness and for the conservation of the migratory process as well.