BARRED OWL RANGE EXPANSION INTO THE CENTRAL IDAHO WILDERNESS

During the past century the geographic range of the Barred Owl (Strix varia) has expanded in western North America beginning in Alberta and British Columbia and moving southward in the United States. The patter n of range expansion remains poorly documented and several untested ex planatory hypotheses have been proposed. We surveyed for owls in centr al Idaho from 1980-95 and recorded the occurrence of Barred Owls (1980 -93 surveys did not employ playback calls of Barred Owls). Despite num erous surveys for owls across a broad range of habitats, we did not en counter Barred Owls until 1985. Thereafter, we heard them regularly at several sites in central Idaho. We encountered Barred Owls most frequ ently in upland mature and old-growth mixed conifer forests. We sugges t that expanding Barred Owl populations reached central Idaho very rec ently, possibly in the early to mid-1980s. Although earlier reports of expanding Barred Owl populations in western North America focused mai nly on managed forest lands with extensive timber harvest, forest cond itions within designated wilderness also apparently support expanding Barred Owl populations. Range expansion by this species in western Nor th America is especially surprising in light of the limited range of a close congener, the Spotted Owl (Strix occidentalis), in the region.