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    Author(s): Eric D. Forsman; Robert G. Anthony; E. Charles Meslow; Cynthia J. Zabel
    Date: 2004
    Source: J. Raptor Res. 38(3): 214-230
    Publication Series: Scientific Journal (JRNL)
    PDF: Download Publication  (2.8 MB)


    We describe local, regional, and annual variation in diets of northern Spotted Owls (Strix occidaatalis caurina) in Oregon based on 24497 prey collected at 1118 owl territories in 1970-2003. The sample included 91.5% mammals, 4.3% birds, 4.1% insects, and 0.1% other prey. The diet included 2131 species, including 49 mammals, 41 birds, 3 reptiles, 1 frog, 1 crayfish, 1 scorpion, 2 snails, and 33 species of insects. On average, 91.9 ± 0.3% (SE) of prey in the diet were nocturnal animals, 3.3 ± 0.2% were diurnal, and 4.8 ± 0.2% were active both day and night. Of the prey captured, 50.5 ± 0.8% were arboreal, 18.7 ± 0.7% were scansorial, 4.8 ± 0.2% were aerial, and 26.0 ± 0.7% were terrestrial. Mean mass of prey was 116.6 ± 6.5 g. Diets varied among owl territories, geographic regions, and years; but were generally dominated by four to six species of nocturnal mammals, including northern flying squirrels (Glaucomys sabrinus), woodrats (Neotoma fuscipes and N. cinerea), red tree voles (Arborimus longicaudus), western red-backed voles (Clethnonomys californicus), deer mice (Peromyscus maniculatus), or gophers (Thomomys spp.). Estimates of dietary evenness were low, indicating diets dominated by a few species of mammals. Forest management practices that produce healthy populations of arboreal and scansorial mammals such as flying squirrels, woodrats, and red tree voles should benefit northern Spotted Owls in Oregon and Washington.

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    Forsman, Eric D.; Anthony, Robert G.; Meslow, E. Charles; Zabel, Cynthia J. 2004. Diets and foraging behavior of northern spotted owls in Oregon. J. Raptor Res. 38(3): 214-230


    northern spotted owl, Strix occidentalis caurina, diet, prey selection, northern flying squirrel, Glaucomys sabrinus, red tree vole, Arborimus longicaudus

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