Is diet adaptability a reason for the persistence of African Crowned Eagles Stephanoaetus coronatus in altered habitats?

Abstract

The dietary response of African Crowned Eagles Stephanoaetus coronatus to habitat transformation was investigated. Habitat alteration around nests in the Eastern Cape, South Africa, was mapped and nests were assigned to two habitat classes. Prey remains were collected from around nests and identified by comparison with reference specimens and images and descriptions from the literature. Prey proportions were compared between ‘intact’ (n = 6) and ‘altered’ habitat classes (n = 6), and the Shannon–Wiener diversity index was calculated for each. Notwithstanding bias associated with the use of prey remains to investigate diet, the aims of the study were achieved. Rock Hyrax Procavia capensis was the primary prey in both habitat classes. In ‘altered’ habitats, the eagles took a larger proportion of species that are associated with open (e.g. hares Lepus spp.) and altered habitats (e.g. Vervet Monkey Chlorocebus pygerythrus) and a lower proportion of forest specialist species (e.g. Blue Duiker Philantomba monticola). Diet diversity was significantly higher in ‘altered’ habitats. Our data suggest that persistence of the eagles in altered landscapes can be attributed to two main factors: continued availability of a principal prey species and the ability of the eagles to respond to changes in availability by prey switching.

Keywords: Crowned Eagle, habitat alteration, prey-switching, diet