THE BARRED OWL (STRIX VARIA) INVASION IN CALIFORNIA

We estimated the range expansion of Barred Owls (Strix varia) in Calif ornia and the potential negative effects this species may have on Spot ted Owls (Strix occidentalis). Barred Owl range expansion has been rap id over the past two decades. A total of 61 Barred Owls has been detec ted in 12 different California counties. Barred Owls were first sighte d in California in 1981 in Del Norte and Trinity counties. They now ha ve been detected as far south as Sonoma County in western California a nd Yuba County in the Sierra Nevada. The ratio of new Barred Owl sites found per new Spotted Owl territory has increased from one per 50 Spo tted Owl territories in the 1980s to one per 10 to 20 new Spotted Owl territories in the mid 1990s. This suggests that the Barred Owl popula tion in California is increasing. In addition seven Barred Owl x Spott ed Owl hybrids have been reported in California. Because of the potent ial for hybridization, competition for food and habitat, and predation , it appears that the Barred Owl could influence Spotted Owl populatio ns negatively.