Foraging Habitat and Home-Range Characteristics of California Spotted Owls in the Sierra Nevada

Abstract

We examined habitat use patterns at two spatial scales among six radio-tagged California Spotted Owls (Strix occidentalis occidentalis) in the Sierra Nevada. Foraging owls selected macrohabitats composed of larger trees (>52 cm dbh) with canopy closures of 40% and greater. Owls used forests composed of medium trees (28-52 cm dbh) and habitats with less than 40% canopy closure, which is less frequently than expected. Fewer than 2% of telemetry locations occurred in clearcut/shrub/plantation habitat which represented 30% of available habitat. Foraging owls used microhabitats that were characterized by multiple vegetative strata, large tree size classes, high tree basal areas and woody debris. The median 100% minimum convex polygon home-range was 1,439 ha (n = 5, June to December, 1987). Telemetry locations were statistically independent when separated by five days. Estimates of minimum convex polygon and modified minimum convex polygon size based on statistically independent telemetry data were significantly smaller than estimates based on continuous and single-observation monitoring.