Since their range expansion into the Pacific Northwest, anecdotal evidence suggests that northern barred owls (Strix varia varia) may be displacing northern spotted owls (Strix occidentalis caurina). My objectives were to characterize barred owl distribution and population increase in Oregon, investigate spotted owl territory performance before and after barred owl detection, and document cases of hybridization between barred owls and spotted owls. Between 1974-1998, 706 unique barred owl territories were reported in Oregon. At five spotted owl demographic study areas in Washington and Oregon, barred owl detections increased rapidly between 1987-1999. After barred owls were detected within 0.80 km of the spotted owl territory center, occupancy of spotted owls declined, and there was a significant likelihood of spotted owl displacement when barred owls were either currently or previously present. When barred owls were detected between 0.81-2.40 km from the spotted owl territory center, there was no difference in mean occupancy of spotted owls after barred owls were detected, and spotted owl detection rates when barred owls were currently or previously present were not significantly different from territories without barred owls. There was no effect on spotted owl reproductive performance after barred owls were detected within 0.80 km or between 0.8 1-2.40 km of the territory center. When barred owls were detected within 0.80 km of a spotted owl territory center, 46% of the spotted owls moved> 0.80 km and 39% were never found again. In comparison, at territories without barred owls, only 21% of spotted owls moved> 0.80 km, and only 11% disappeared completely. When barred owls were detected between 0.81-2.40 km from the territory center there was no difference in rates of movement or disappearance of spotted owls between territories with and without barred owls. Reports of hybridization between spotted owls and barred owls are uncommon. Between 1974 and 1999, 24 adult and 26 juvenile hybrids were confirmed in Washington and Oregon. Data from this study suggest that barred owls pose a threat to spotted owls but it is too soon to predict whether trends observed in this study will continue, or will spread to other areas.

Conclusions, and Recommendations P.75

Owls in Australia are difficult to find and study, so comparatively little is known about their biology. Even less is known about the status, taxonomy, and biology of those species and sub-species living in tropical and subtropical environments and on islands. Many island species and subspecies are at risk, some have already been lost. Ecology and Conservation of Owls includes sections on population ecology, distribution, habitat and diet, conservation and management, and voice structure and taxonomy. It contains a number of review chapters that bring together findings from a wide range of previous research, including recent developments in owl taxonomy and systematics, and studies of population limitation in northern hemisphere owls. The chapters in this book derive from papers presented at the Owls 2000 conference held in Canberra, Australia, which was third in a series of international meetings on owls.

A fascinating introduction to the biology, life cycle, and behavior of owls Illustrated with gorgeous watercolor paintings and full-color photography Features an identification guide to all North American species Owls have always occupied a special place in the popular imagination, regarded throughout history as both harbingers of doom and symbols of wisdom. In this newest title in Stackpole's Wild Guide series, author Cynthia Berger explores the lives of these mysterious creatures, including their fearsome hunting abilities, their surprisingly tender courtship rituals, and, of course, their haunting vocalizations. Also included is an identification guide covering the full range of North American species-from the tiny Elf Owl to the imposing Great Gray Owl-as well as tips for observing owls in the wild. There are even instructions for building your own nest box to attract these remarkable birds to your backyard.