Landscape composition around northern spotted owl nests, central Cascade Mountains, Oregon

Graduation date: 1998This study describes the composition of forest landscapes surrounding\ud northern spotted owl (Strix occidentalis caurina) nests in the central Cascade\ud Mountains of Oregon. I compared forest composition around 126 owl nests in 70 pair\ud territories with forest composition around 119 points drawn randomly from all\ud terrestrial cover-types, and around 104 points drawn randomly from the old-forest\ud (closed canopy, > 80 yrs) cover type. All nest sites and random points were drawn\ud from U.S. Forest Service lands and were not drawn from privately owned lands or\ud Wilderness Areas.\ud Forest cover was classified on a Landsat Thematic Mapper image. I quantified\ud the percentage of old-forest within 200 concentric circular plots (0.04-5.0-km radii),\ud centered on each analyzed point, using a geographic information system. I used\ud logistic regression to make spatially-explicit inferences.\ud Owl nests were surrounded by more old-forest when compared to points\ud drawn randomly from all terrestrial cover types: there was significantly (P<0.05)\ud more old-forest around the owl nests in plots as large as 1.79 km in radius. When\ud compared to points drawn randomly from the old-forest cover type, owl nests were\ud surrounded by significantly (P