Spatial and temporal variation in diets of Spotted Owls in Washington

摘要: --We studied diets of Northern Spotted Owls (Strix occidentalis caurina) in three different regions Washington State during 1983-96. flying squirrels (Glaucomys abrinus) were the most important prey areas, comprising 29-54% numbers and 45-59% biomass. Other included snowshoe hares (Lepus americanus), bushy-tailed woodrats (Neotoma cinerea), boreal red-backed voles (Clethri0n0mys gapperi), mice (Peromyscus maniculatus, P oreas). Nonmammalian generally comprised less than 15% Mean mass was 111.4 _+ 1.5 g on Olympic Peninsula, 74.8 +_ 2.9 Western Cascades, 91.3 1.7 Eastern Cascades. Diets varied among territories, years, seasons. Annual variation diet characterized by small changes relative occurrence types rather a complete restructuring diet. Predation primarily restricted to juveniles captured spring summer. did not differ between nesting nonnesting owls 19 21 territories examined. However, direction difference positive 15 cases (larger mean fbr owls), suggesting trend toward larger samples collected f•om owls. We suggest hat differences seasons, are probably due abundance. there other fhctors that could cause such differences, including individual selection, timing pellet collections, accessibility cover types.