Diet composition of Common Kestrels Falco tinnunculus and Long-eared Owls Asio otus coexisting in an urban environment

Abstract

We studied the dietary composition of urban populations of Common Kestrels (Falco tinnunculus) and Long-eared Owls (Asio otus) under fluctuating vole abundance in Ceske Budejovice during 2002-2005. Common Voles were the dominant prey. In poor vole years, the dietary proportion of alternative prey increased in both species. Long-eared Owls fed more on mice and related rodents, whereas the Common Kestrels' diet shifted to insects. The different alternative diets may be due to species-specific daily activity, hunting techniques and/or hunting habitats. Furthemore, we examined the possible relationship between the distance from a nest to the city centre and the proportion of voles in the diet. The Kestrel diet was not markedly influenced by distance, but for Long-eared Owls an increasing distance was associated with an increasing dietary proportion of voles.