OBSERVATIONS ON EAST AFRICAN BIRDS OF PREY

Abstract

SummaryEast Africa is a country very rich in birds of prey, both resident and migrant, partly because a majority of migrant Eurasian birds of prey enter Africa through Suez in winter. Diurnal birds of prey are both more numerous and more varied than nocturnal, especially among migrant species.The size range of birds of prey, both diurnal and nocturnal, in East Africa is nearly equivalent to that occurring in the whole world. The predator‐prey relationship is thus exceedingly complex in East Africa.Diurnal birds of prey hunt by sight and nocturnal by the use of sight and hearing. Diurnal birds of prey can thus make use of both live and dead prey, but owls are only able to capture living prey and do not feed upon carrion.Almost all animals in East Africa, from elephants to small insects, are either eaten as carrion or preyed upon as live prey by some species of raptor. Most live animals in the size range from small insects to animals 5 kg in weight are preyed upon by a diurnal or a nocturnal bird of prey at some stage of the twenty‐four hours. Carrion is not consumed by birds of prey at night.Comparison of the raptor avi‐fauna of forests with that in savannah indicates that in forests raptors are much less likely to eat carrion than in open country, but that the size range of raptors preying upon live animals is much the same in forests and in open country. Nocturnal birds of prey are less successful in a forest environment than are diurnal species.The possible effect of individual species (Aquila wahlbergi and Polemaetus bellicosus) and of a combination of many species on the possible population of animals in home ranges of known size is discussed. It is concluded that there is no evidence that either an individual species or a combination of several could effectively limit the populations of certain prey species.Concentrations of several breeding pairs of large raptors in apparent association with one another are mentioned. The interrelations of such species, and the effects of possible competition between members of such associations, are discussed. It is concluded that real competition is likely to be slight and that such groups of nesting raptors must be due to a form of inter‐specific gregariousness.