Characteristics of young forests used by spotted owls on the western Olympic Peninsula, Washington

Although the dependence of spotted owls (Strix occidentalis) on older fores ts has been well documented, the specific attributes of comparatively young er forests used by owls have not been described in some regions. We collect ed habitat data at locations used by spotted owls tracked in an intensive r adio-telemetry study to develop descriptions of these forests on the wester n Olympic Peninsula. Washington. After addressing the effects of triangulat ion error on the placement of our vegetation sampling plots, we collected d ata at all 16 telemetry locations that could be clearly associated with non -old-growth habitat, as well as 16 random locations. Owl locations were div ided into 2 groups to reflect single-use (only one radio location within th e error polygon) and multiple-use sites (greater than or equal to 2 radio l ocations within the error polygon) within home ranges. Vegetation data coll ected in three arrays of variably-sized plots included measures of stem and snags density (by diameter class), canopy cover, and cover of downed wood and shrubs. Our analyses indicated that single-visit and random locations d id not differ with respect to the variables we recorded. However, both diff ered from multiple-use locations in abundance of larger snags. and amount o f canopy closure. A logistic regression model indicated that multiple-use s ites could be reliably distinguished from single-use and random locations b ased on the greater number of snags greater than or equal to 51 cm diameter at breast height (dbh) and greater than or equal to 70% canopy closure. Yo unger forests managed for spotted owl foraging habitat in this region shoul d be in the understory reinitiation stage of stand development, have greate r than or equal to 70% canopy closure, and contain greater than or equal to 4 snags/0.4-ha that are greater than or equal to 51 cm dbh. The habitat de finitions we propose may not be applicable to other areas characterized by different forest types and prey assemblages.