Role of disturbance, geology and other environmental factors in determining abundance and diversity in coastal avian communities during winter

摘要

Wading birds are important predators in intertidal communities. Their ecology and distribution have been widely studied in estuarine wetlands, but little is known about the factors determining their abundance and diversity in the more common non-estuarine coasts. We analysed data from a large-scale survey of wader (Charadrii) populations in the non-estuarine coasts of Portugal (length = 1096 km), during winter, together with variables related to disturbance, habitat and geophysical characteristics of the coast to explain the patterns of wader abundance and diversity. The wintering community is composed of 13 species and dominated by ruddy turnstones Arenaria interpres and sanderlings Calidris alba. Wader abundance was limited by direct disturbance from humans and the presence of peregrine falcons Falco peregrinus. Overall human presence, availability of rocky intertidal areas, presence of nearby estuarine wetlands and low winter temperatures favoured higher wader densities. Areas dominated by igneous and metamor-phic rocks (basalts, granites, schists and greywackes, and diabases) harboured a more diverse wader community than areas with sedimentary rocks or with sandy beaches, suggesting that coastal geology may have a structuring role for wader communities, which had not yet been described. Understanding these patterns gives useful directions as to where one should focus conservation efforts in non-estuarine coastal areas.