When the Northern Spotted Owl (Strix occidentalis caurina) was federally listed as a threatened species in 1990, environmental groups working in the Pacific Northwest quickly embraced the animal as a mascot for the natural areas of the region.
Studies conducted early in the decade indicated that the birds had a strong affinity for old growth trees, and the mature forests were assumed to be equivalent to Spotted Owl habitat.
In the last decade, many acrimonious battles have been pitched over the fate of land which is simultaneously home to the owls and full of economically valuable timber. But beneath the din of these conflicts, little attention has been paid to other factors which may be influencing the species.
Results from a long-term study published this month by the Ecological Society of America provide insight into the population dynamics of these birds of prey and explore the role which climate and habitat quality play in determining the survival of this species.
The study, published in the peer-reviewed ESA journal Ecological Monographs (Vol. 70 no.4), was conducted by Alan B. Franklin and David Anderson of the US Geological Survey at Colorado State University, and R. J. Gutierrez and Kenneth P. Burnham of Humboldt State University (now at the University of Minnesota and the US Geological Survey of Colorado State University, respectively).
The team analyzed data from a ten year study in the forests of Northwestern California where owls were surveyed, their reproductive output recorded, and relative fitness estimated.
The study area, which is centered around Trinity River east of
Eureka, is located upon land managed by the US Forest Service and
the Bureau of Land Management. The area is considered to be one of
the most complex and diverse in the western United States due to its
unique blend of coniferous and hardwood trees. The area is logged,
however, by timber c
Contact: Alison Gillespie
202-833-8773 ext 211
Ecological Society of America