INFLUENCE OF SMALL MAMMALS ABUNDANCE ON THE NUMBER AND SELECTION OF HABITATS BY LONG-EARED (ASIO OTUS) AND SHORT-EARED (ASIO FLAMMEUS) OWLS

The differences between the quality of habitats occupied by the short-eared (Asio flammeus) and the long-eared (Asio otus) owls, which inhabit open sites, including agricultural lands, were revealed. The habitat quality was assessed according to the abundance and the species diversity of potential preys of mammals (voles and insectivorous animals). Short-eared owls preferred habitat patches with the higher number of potential prey species and the higher abundance of small mammals, than those in the adjacent territories. In contrast, the overall abundance of potential preys in the territories of long-eared owls did not differ from that in the adjacent areas. Probably, this fact attests that the structural characteristics of habitats and the local prey distribution are of not importance for these owls. The number of long-eared owl was related only to the group of voles that preferred dry habitat (r(s) = 0.94, p < 0.001). The number of short-eared owls was closely related with the abundance of the species groups preferred both dry (r(s) = 0.98, p < 0.001) and wet (r(s) = 0.89, p = 0.015) habitats. The abundance of the common vole, Microtus arvalis, had a significant effect on the numbers of both owl species (p < 0.05). For the short-eared owl, the abundance of the root vole, M. oeconomus (p = 0.03), and the common shrew, Sorex araneus (p = 0.05), was also important.