Pacific Northwest Research Station

Title: Diets and foraging behavior of northern spotted owls in Oregon.

Author: Forsman, Eric D.; Anthony, Robert G.; Meslow, E. Charles; Zabel, Cynthia J.

Date: 2004

Source: J. Raptor Res. 38(3): 214-230

Description: 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.

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

View and Print this Publication (2.8 MB)

Pristine Version:  An uncaptured or "pristine" version of this publication is available. It has not been subjected to OCR (Optical Character Recognition) and therefore does not have any errors in the text. However it is a larger file size and some people may experience long download times. The "pristine" version of this publication is available here:

View and Print the PRISTINE copy of this Publication (2.7 MB)

Publication Notes: 

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
• This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

 Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

Citation

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