Dietary variations of the Ural Owl Strix uralensis in the transitional mixed forest of northern Belarus with implications for the distribution differences

Abstract

The dietary structure and distribution patterns of the Ural Owl Strix uralensis under conditions of different food supply (seasonal and year-to-year changes and landscaperelated differences) in the coniferous small-leaved transitional forest of northern Belarus were studied in 1996-2002 . In total, 1474 prey individuals were recovered from the 447 pellets analysed, and a census of Ural Owl active territories was done each year in early spring in the two study plots. In the ecologically rich area in the Gorodok district the Ural Owl population was high and evenly spaced, while in the poor habitats of the Polotsk district, where the abundance of small mammals was tenfold lower, the Ural Owl was fairly rare (about eight-fold less) with a patchy distribution . In both study areas, Ural Owls took many bank voles, which is the most common forest rodent in each area . During population peak periods of Microtus voles, Ural Owls tended to rely much on this prey category. A positive correlation in the abundance indices of the Ural Owl in the current spring and of the bank vole in the preceding spring was observed. The variety of obtained data strongly suggests that the bank vole is the key prey species for the Ural Owl in the transitional forest of northern Belarus, and both the landscape-related differences in the predator distribution and the between-year variations in its abundance are seemingly determined by the distribution patterns and population dynamics of the bank vole .