The range expansion by barred owls (Strix varia) into western North America has raised considerable concern regarding their potential effects on declining northern spotted owl (Strix occidentalis caurina) populations, yet most information on the occurrence of barred owls in the region is limited to incidental detections during surveys for spotted owls. To address this shortcoming we investigated response behavior, detection probabilities, and landscape occupancy patterns of barred owls in western Oregon, USA, during conspecific versus spotted owl call-broadcast surveys. Subtle differences in barred owl response behavior to conspecific versus spotted owl vocalizations combined with minor procedural differences between species-specific survey protocols led to a sizeable difference in estimated detection probabilities during conspecific (0.66, 95% CI = 0.61–0.71) versus spotted owl (0.48, 95% CI = 0.39–0.56) surveys. We identified 61 territorial pairs of barred owls during repeated surveys of a multi-ownership study area with the probability of occupancy being highest in the structurally diverse mixture of mature and old forests that occurred almost entirely on public lands. Our findings suggest that research and management strategies to address potential competitive interactions between spotted owls and barred owls will require carefully designed, species-specific survey methods that account for erratic response behaviors and imperfect detection of both species. Our sampling methods can be used by forest managers to determine the occurrence and distribution of barred owls with high confidence.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 75 • No. 3