We estimated diet composition of sympatric Mexican spotted (Strix occidentalis lucida, n = 7 pairs of owls) and great horned owls (Bubo virginianus, n = 4 pairs) in ponderosa pine (Pinus ponderosa) - Gambel oak (Quercus gambelii) forest, northern Arizona. Both species preyed on mammals, birds, and insects; great horned owls also ate lizards. Mammals dominated the diet of both species. Mammals comprised 63 and 62% of all prey items identified in diets of spotted and great horned owls, respectively, and 94 and 95% of prey biomass. Both species primarily preyed on a few groups of small mammals. Observed overlap in diet composition between species (0.95) was greater than expected based on null models of diet overlap, and the size range of prey taken overlapped entirely. Mean prey mass was similar for both species (great horned owl, 47.0 ± 7.4 g [SE], n = 94 items; spotted owl, 40.1 ± 1.8 g, n = 1,125 items). Great horned owls consumed larger proportions of diurnally active prey than spotted owls, which primarily consumed nocturnally active mammals. Our results, coupled with a previous analysis showing that these owls foraged in the same general areas (Ganey and others 1997), suggests that they could compete for food resources, which are assumed to be limiting in at least some years. They may minimize the potential for resource competition, however, by concentrating foraging activities in different habitats (Ganey and others 1997) and by foraging at different times, when different suites of prey species are active.

Most owls are almost perfectly adapted to life in the dark. Their vaguely humanoid faces reflect the spectacular evolution of their hearing and vision, which has made flight, romance, and predation possible in the near absence of light. This accessible guide, full of intriguing anecdotes, covers all 19 species of owls occurring in North America. More than an identification guide, Field Guide to Owls of California and the West describes the biology and behavior of owls to make finding and identifying them easier and watching them more enjoyable. The guide also explores the conservation challenges that owls face and tells how owls provide insights to scientists working in fields from technology to health. * Color plates illustrate each species * Range maps show the western distribution of North America's owls, 14 of which occur in California * Offers tips for finding and watching owls * Gives information on how to design, place, and maintain nest boxes * Describes human attitudes toward owls through history, including in Native American cultures of the West

The eastern screech owl, widespread over the eastern half of North America and noticeably tolerant of human activity, is one of America's most familiar birds. Residing naturally in wooded environs with tree cavities, this owl lives well in suburbia and can be found nesting in mailboxes, porch columns, and purple martin houses. Based on a twenty-five-year study, biologist Frederick R. Gehlbach tells the life story of the eastern screech owl, focusing on case studies of suburban and rural study plots in Central Texas. This is the first thorough study of major life-history, behavioral, and ecological features of the species. Indeed, it is the first concurrent, comparative study of an urban and a rural population of any New World animal. Told in a personal voice, the story of these birds will interest all who have not lost touch with their ancestral world. However, Gehlbach has also included quantitative data and analysis of interest to ecologists, wildlife biologists, and ornithologists. Photographs (including color shots of the gray and rufous phases), figures, and tables provide further detail. Gehlbach's investigations have been those of not only an academic ecologist, but a suburbanite curious about his natural surroundings. The result is a model of research on species population dynamics and adaptation, yielding an emerging picture of what the eastern screech owl needs for successful coexistence with human neighbors.

A comprehensive reference discusses all aspects of raptors, including their biology, habitat, and behavior, and offers identification information.

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.

That is what this book is about. It is a framework for planning, in which habitat is the key to managing wildlife and making forest managers accountable for their actions. This book is based on the collective knowledge of one group of resource professionals and their understanding about how wildlife relate to forest habitats. And it provides a longoverdue system for considering the impacts of changes in forest structure on all resident wildlife.