Nest-site selection and reproductive success of California spotted owls

We evaluated quality of nesting habitat and nest site selection of an insular population of California Spotted Owls (Strix occidentalis occidentalis). We assessed habitat structure for successful and unsuccessful nests from 103 independent territories at three spatial scales, and habitat selection by comparing nest stand structure with identical variables from random points. Fledgling success was unrelated to nest type, nest tree, nest stand characteristics, or habitat type. However, nest productivity was greatest in lower elevation oak/big-cone fir habitat (1.7 fledglings per successful nest). Nest stands were characterized by greater variation in tree size, higher canopy closure, and greater basal area of large trees compared with random points. We were able to differentiate consistently between nest and random points using discriminant function models (≃79% correct classification). Our results confirm previous observations that California Spotted Owls will use a variety of habitats, but these habitats are consistently characterized by greater structural complexity compared with available habitat.