Nest Sites and Nesting Habitat of the Northern Spotted Owl in Northwestern California

Abstract

We located 69 Spotted Owl (Strix occidentalis caurina) nests in northwestern California. Spotted Owls nested in eight different tree species of which 83% were located in Douglas-firs (Pseudotsuga menziesii). Sixty percent of the nests were located in broken-top trees, whereas cavity and platform nests each accounted for 20%. Minimum nest tree ages averaged 288 years (range 57-688) with 42% of the trees having minimum ages of > 300 years. Owls nested in forests that were structurally different than forests available to them. These stands were characterized by large (> 90 cm dbh) conifers, a hardwood understory, and a variety of tree sizes. Nest sites appeared to be located in pockets of even older forest containing disfigured trees of advanced age which provided suitable nesting structures.