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Demography of Northern Spotted Owls in southwestern Oregon

Studies in Avian Biology

By:
and
Edited by:
Eric D. Forsman, Stephen Destefano, Martin G. Raphael, and R.J. Gutierrez

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Abstract

Northern Spotted Owls (Strix occidentalis caurina) are associated with lower elevation, commercially valuable, late-successional coniferous forests in the Pacific Northwest. Meta-analyses of demographic parameters indicate that Northern Spotted Owl populations are declining throughout their range (Anderson and Burnham 1992, Burnham et al. this volume). Recent research has attempted to determine whether management activities have affected the viability of Spotted Owl populations, and results have led to development of conservation plans for the species (Dawson et al. 1987, Thomas et al. 1990, Murphy and Noon 1992, USDI 1992, Thomas et al. 1993b).

In the Recovery Plan for the Northern Spotted Owl (USDI 1992b) threats to the species were identified as small population sizes, declining populations, limited amounts of habitat, continued loss and fragmentation of habitat, geographically isolated populations, and predation and competition from other avian species. Weather and fire are natural processes that also may affect reproductive success of Spotted Owls. Weather may be a factor in the high annual variability in fecundity of Spotted Owls, as has been suggested for other predatory bird species (Newton, 1979, 1986). However, these factors have not been addressed in previous studies of Spotted Owls.

Our objectives were to estimate survival, fecundity, and annual rates of population change (l) for resident, territorial female Spotted Owls at two study areas in the coastal mountains of southwestern Oregon. We tested if the amount of rainfall was correlated with reproduction of Spotted Owls. While surveying for Spotted Owls, we documented the increased presence of Barred Owls (Strix varia), a potential competitor of Spotted Owls.

Additional publication details

Publication type:
Book chapter
Publication Subtype:
Book Chapter
Title:
Demography of Northern Spotted Owls in southwestern Oregon
Series title:
Studies in Avian Biology
ISBN:
0935868836
Volume:
17
Year Published:
1996
Language:
English
Publisher:
Cooper Ornithological Society
Contributing office(s):
Forest and Rangeland Ecosystem Science Center
Description:
6 p.
Larger Work Type:
Book
Larger Work Subtype:
Conference publication
Larger Work Title:
Demography of the Northern Spotted Owl
First page:
77
Last page:
82
Conference Location:
Fort Collins, CO
Conference Date:
December, 1993
Country:
United States
State:
Oregon