Diet of tawny owls (Strix aluco) in relation to field vole (Microtus agrestis) abundance in a conifer forest in northern England

摘要: The diet of tawny owls Strix aluco was determined from pellets and prey items in owl nests Kielder Forest, a planted spruce forest northern England. Field voles Microtus agrestis were their most important food, formed the highest proportion winter early spring. Common shrews Sorex araneus, common frogs Rana temporaria birds taken more frequently late spring summer. Clear cuts, areas which timber had been felled at end rotation, provided main field vole habitat remained suitable for 10–15 years after re-planting. abundance measured three times year on numerous clear cuts throughout study area using sign index based fresh grass clippings runways. Tawny responded functionally to 3 4-year cycles abundance. In when scarce, adult took frogs, as pellet analysis. contrast, bird fed nestlings nests. proportions changed over 19-year period. More bank Clethrionomys glareolus wood mice Apodemus sylvaticus occurred every 1992 than any before this. Numbers increased significantly period, whereas numbers exhibited non-cyclic, multi-annual fluctuations that unrelated cycles. It is argued rodent reflected changes guilds area; reasons this are discussed. This first forests Britain highlights value such large-scale dynamic habitats populations predators.