Using ecological-niche modeling to predict Barred Owl invasions with implications for Spotted Owl conservation

The Spotted Owl (Strix occidentalis) is the focus of intense concern as a species threatened by the destruction and fragmentation of primary forest in the Pacific Northwest (U.S.A.). Aside from habitat concerns, an additional peril exists for the species: the larger and snore aggressive Barred Owl (S. varia) is invading the Pacific Northwest and has the potential to overrun much of the range of the endangered species. We evaluated the dimensions of this potential invasion by using ecological niche models based on point-occurrence data. With these tools, we developed models with significant predictions for the native distributions of both Spotted and Barred owls (tested via independent occurrence data) and for the invasive range of Barred Owls. Overlap between the models for the two species suggests that most of the northern portion of the Spotted Owl's distribution (south to about lest. 38degreesN) is vulnerable to Barred Owl invasion. We present an example of the potential effects of species invasions on endangered species conservation.