Predation by the Barn Owl (Tyto alba) in Mediterranean Habitats of Chile, Spain and California: A Comparative Approach

Abstract

We show that the Mediterranean habitats of Chile, Spain and California are characterized by similar size distributions of small mammal species available to raptors, and that these prey resources are exploited by taxonomically related assemblages of owl species that exhibit similar distributions of body size. Barn owls (Tyto alba) in the three mediterranean areas are similar in that they take almost every small mammal species present. However, Spanish barn owls differ from those in Chile and California in that they take significant amounts of insects, amphibians and reptiles, and also in that the mean size of mammalian prey in their diet is considerably smaller than that for Chilean and California barn owls. These features are attributed to the reduced abundance of larger-sized small mammals in Spain, which presumably forces the barn owls to prey more heavily on the smallest mammals available and also on low-reward nonmammalian prey. The trophic parameters of barn owls in a Colorado grassland fall well within the range of variation exhibited by mediterranean barn owls and this is, associated with size distributions of mammalian prey and of syntopic owls which are similar between the two habitat types. The essential features determining the predation pattern of the barn owl in different parts of its range seem to be the statistical distribution of mammalian prey sizes available, the relative abundance of these prey and the configuration of the assemblage of syntopic owls.