First Advisor

Richard B. Forbes

Date of Publication

1982

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Biology

Department

Biology

Language

English

Subjects

Red-tailed hawk, Birds -- Oregon -- Sauvie Island

DOI

10.15760/etd.3169

Physical Description

1 online resource (57 p.)

Abstract

A study was undertaken to determine the abundance, distribution, perching heights, diets and territory sizes of Red-Tailed Hawks on Sauvie Island, Oregon. Sauvie Island supported a large wintering population of non-territorial Red-Tailed Hawks. The establishment of territories began around 10 January. Average perch height was found to be 14.2 m. Average perch height increased from fall to spring, corresponding-to the onset of the breeding season and to the onset of egg-laying and incubation. Voles (Microtus spp.) were the principal prey year-round, though waterfowl were more important in terms of biomass in the winter and early spring. Territory sizes on the Island ranged from .31 - 3.73 km squared The abundance of voles was assessed in different habitats within five Red-Tailed Hawk territories. Territory size was shown to be inversely correlated to the population density of voles. The implications of this finding for the type of territoriality exhibited by Red-Tailed Hawks is discussed, as are some proximate factors affecting habitat selection.

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Comments

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Persistent Identifier

http://archives.pdx.edu/ds/psu/18376

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