Diet of the African black oystercatcher Haematopus Moquini on rocky shores: spatial, temporal and sex-related variation

Abstract

The diet of the African black oystercatcher Haematopus moquini was investigated throughout the species’ range. Variation in diet is related to time, place and sex of the bird. Correspondence analysis, using simple graphical displays, was chosen as the most appropriate technique for describing regional and local variation. Principal prey species on the west coast are mussels Choromytllus mendlonalis and Aulacomya ater, and limpets Patella granulans and P. argenvillei. The mussel Pema pema predominates In the diet on the south and south-east coasts. Less food is taken by night than by day, and at night the nocturnally active Patella granulans forms a much greater proportion of the diet than by day. An increasing proportion of mussels and correspondingly fewer limpets are fed to chicks as they grow older. Territorial pairs reduce potential intersexual competition for food by removing prey In differing relative proportions: males take more limpets and whelks while females take a greater proportion of polychaetes and small unshelled items. Diet separation is a function of bill dimorphism. Small prey items generally are not selected, and prey size selection is consistent within prey species and between localities.