Forest stand structure of the northern spotted owl's foraging habitat

• Published in: Forest science Vol. 45; no. 4; pp. 520 - 527
• Main Authors: North, M.P, Franklin, J.F, Carey, A.B, Forsman, E.D, Hamer, T
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Society of American Foresters 01-11-1999
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; endangered species; foraging; Fundamental and applied biological sciences. Psychology; habitat selection; old-growth forests; stand structure; Strix occidentalis; Synecology; Terrestrial ecosystems; virgin forests; Washington; Forest stand; Silviculture; Strix occidentalis; Picea sitchensis; Polystichum munitum; Ecology; Pteridophyta; Vertebrata; Animal plant relation; Dicotyledones; Thuja plicata; Angiospermae; Softwood forest tree; Gymnospermae; Coniferales; Spermatophyta; Habitat; Tsuga heterophylla; Aves; Oxalidaceae; Vegetation structure; Filicineae; Canopy(vegetation)
• ISSN: 0015-749X; 1938-3738
• DOI: 10.1093/forestscience/45.4.520

Although the spotted owl's close association with old growth has been extensively studied, it has been more difficult to identify and quantify the abundance of particular stand structures associated with preferred owl foraging sites. Old-growth forests have a suite of characteristics that distinguish them from younger forests but which also make it difficult to isolate individual structural features important to the spotted owl. This study used an analysis of use-only sites in areas where natural disturbance had created a gradient of old-growth structural characteristics. We used radio telemetry data collected from reproducing owl pairs to locate sample stands and compute a relative measure of owl-use intensity in each stand. Snag volume and tree height class diversity (a measure of canopy layering) were the stand structures significantly associated with owl foraging intensity. Stands with 142 m3/ha of intact snags and a high diversity of tree heights had medium or high foraging use by spotted owls. In these old-growth stands, biological legacies (e.g., large trees and snags) produced by past disturbance provide important forest structures associated with spotted owl foraging use.