Comparison of trends in abundance of guano-producing seabirds in Peru and southern Africa

Abstract

The abundant guano-producing seabirds in Peru and southern Africa feed mainly on the large populations of anchovy Engraulis spp. and sardine Sardinops sagax supported by the Humboldt and Benguela upwelling systems. Numbers of guanay cormorants Phalacrocorax bougainvillii in Peru and the breeding population of Cape cormorants P. capensis in South Africa are significantly related to the biomass of anchovy. For both species, reproductive success decreases in periods of anchovy scarcity, and there may also be substantial adult mortality. There has been long-term stability in numbers of Peruvian boobies Sula variegata, whereas the numbers of Cape gannets Morus capensis decreased as sardine decreased in southern Africa. Numbers of Peruvian pelicans Pelecanus (occidentalis) thagus are significantly related to the combined biomass of anchovy and sardine in Peru. They have been stable in the long-term. There have been ongoing severe decreases in populations of the Humboldt penguin Spheniscus humboldti and the Afri...