Voedsel van Bosuilen Strix aluco in Drenthe

Food of Tawny Owls is described by means of pellet analysis (n=76o prey items) and prey remains in nestboxes (n=72), collected during 1987-96 in the province of Drenthe. Important prey species were especially Clethrionomys glareolus, Microtus arvalis, M. agrestis and Apodemus sylvaticus. Sorex araneus/coronatus and birds are important substitutes in years of scarcity of voles and mice. As compared to other studies in The Netherlands, birds are, however, relatively infrequently taken (Table I), i.e. 7,8% of all prey items versus 31-35% in two other studies. In a well-studied pair, the male took substantially smaller prey than the female, i.e. mean prey weight being respectively 19.3 g (n=lo6) and 35.3 g (n=3o)(Table 2). Sample size is still too small to show sex-specific differences in prey choice.