Temporal changes in prey composition and biomass delivery to African Crowned Eagle nestlings in urban areas of KwaZulu-Natal, South Africa

Abstract

Globally urban areas are expanding rapidly and this usually has negative effects on biodiversity. Despite this, some species manage to persist in urban areas, as is the case with African Crowned Eagles Stephanoaetus coronatus in KwaZulu-Natal, South Africa. As relatively little is known about African Crowned Eagle nestling diet, especially about how it changes with nestling age, we investigated this with nest camera-traps. We analysed temporal changes in prey composition and biomass delivery during the nestling stage. We also recorded which adults provisioned and attended the nest. The main prey fed to nestlings were Rock Hyrax Procavia capensis and Hadeda Ibis Bostrychia hagedash. Adult males did most of the food provisioning, especially at the start of the nestling period. We found a decrease in total prey number and biomass with nestling age. This may be caused by changing requirements of nestlings. Furthermore, delivering fewer prey at later nestling stages may be a facilitating mechanism to enhance fledging of the nestling. Although the total number of prey brought to the nest decreased, we found an increase in numbers of Vervet Monkey Chlorocebus pygerythrus in the diet with nestling age. This indicated an increase in larger prey being delivered to the nests as the nestling aged. We suggest that this could be caused by increased participation in hunting by the larger female as her nest attendance time decreased as the nestling aged. We conclude with emphasising the importance of protecting the Durban Metropolitan Open Space System (D’MOSS) zones for the persistence of this Near Threatened raptor species, and populations of its prey in urban areas for its breeding success.