Barred Owl and Spotted Owl populations and habitat in the central Cascade Range of Washington

The Barred Owl (Strix varia) has continued to expand its range southward in to the northwestern United States from Canada since the 1970s, and has beco me an established member of the forest avifauna in western Washington. Ther e is increasing concern that it may be competing for resources with the thr eatened Northern Spotted Owl (S. occidentalis caurina) throughout its range . We surveyed for Spotted Owls over an extensive area of the central Cascad e Range of Washington during the breeding seasons of 1991-93. Both Spotted Owls and Barred Owls responded to tape recordings and vocal imitations of S potted Owl calls. By using pair responses or grouping single owl responses from close geographic locations on at least three different survey nights, site centers representing probable breeding pairs or territorial single ind ividuals were designated for both species. A total of 53 Barred Owl and 62 Spotted Owl site centers were identified in the 1280 km(2) survey area. Bar red Owls were found at greatest densities on the wetter, western portions o f the Cascade Range. On the driest, eastern portions of this mountain range . Barred Owls were usually found along major river and stream corridors, in the vicinity of forested wetlands, or at higher elevations receiving incre ased precipitation. The compared the extent of mature. young, and other for est habitats at radii of 0.8 and 1.6 km around site centers of both species . Spotted Owls used sites with greater amounts of mature coniferous forest than did Barred Owls within 0.8 km of site centers across all portions of t he study area. Additionally, we found no evidence of mixed-species pairing or hybrids of the two species during the study, suggesting that extensive h ybridization may not be occurring where Barred Owls have become firmly esta blished within the range of the Spotted Owl.