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

Abstract

The distribution of pelagic seabirds off the west coast of southern Africa I S analysed according to trophic guilds. Distribution of the b ~r d s is not random. At any given observation station one guild d o m ~n a t e s the seabird assemblage. P~scivores 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 behaviour and temporal separation. A winter increase in avian species richness and diversity, and abundance and b ~o m a s s , is supported by a seasonal increase in productivity. Correlations of seabird indices with oceanographic and meteorological parameters are poor This indicates that local sedbird distribution is mainly a function of the availability of prey and the species' attributes for locating and capturing prey. However, subsets of parameters for water masses and weather correlate with seabird distribution.