Ecological Structure of the Pelagic Seabird Community in the Benguela Current Region

Abstract

The distribution of pelagic sea birds off the west coast of southern Africa is analyzed according to trophic guilds. Distribution of the birds is not random. At any given observation station 1 guild dominates the sea bird assemblage. Piscivores and squid-eaters account for the bulk of avian abundance and biomass, the remainder being planktivores and omnivores. Intraguild competition for food apparently is reduced by interspecific differences in foraging behavior and temporal separation. A winter increase in avian species richness and diversity, and abundance and biomass, is supported by a seasonal increase in productivity. Correlations of sea bird indexes with oceanographic and meteorological parameters are poor. Local sea bird distribution is mainly a function of the availability of prey and the species'' attributes for locating and capturing prey. Subsets of parameters for water masses and weather correlate with sea bird distribution.