Diets of breeding peregrine and lanner falcons in South Africa

The diets of breeding peregrine (Falco peregrinus) and lanner (F. biarmicus) falcons in South Africa were determined from the analysis of prey remains collected at nest sites and through direct observations to determine the regional variation in peregrine falcon prey and to measure diet overlap, and the potential for competition between peregrine falcons and sympatric congeners. Direct observations suggested that remains under-sampled small prey by about 10% and over-sampled large prey by about 8%. Peregrine and lanner falcons preyed mostly on birds. Pigeons and Streptopelia doves comprised the bulk (38-66% by frequency 68-85% by mass) of the peregrine falcon prey in each of three study areas. Columbids were supplemented by starlings (mostly European starling [Sturnus vulgaris]) on the Cape Peninsula, sandgrouse (Pterocles spp.) and swifts (Apus spp.) on the Orange River, and mousebirds (Colius spp.) in the Soutpansberg. Cape Peninsula peregrine falcons had the least diverse diet, the narrowest feeding niche and they took the largest proportion of juvenile birds. Peregrine falcons on the Orange River had the broadest feeding niche and preyed mainly on ’commuter’ species rather than sedentary residents. Lanner Falcons in the Soutpansberg took mainly terrestrial or cursorial species, particularly young chickens (Gallus gallus, 40%; 37%) and charadriids, but columbids were also important. The diets of sympatric peregrine and lanner falcons overlapped by about 35%. Peregrines falcons concentrated their foraging on woodland and cliff-dwelling prey, while lanner falcons took mainly open-country species. Close-neighboring pairs of congeners did not obviously affect the food-niche parameters of either species suggesting that they were not actively competing for food.