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To investigate whether Northern Goshawk textit(Accipiter gentilis) reproduction is food-limited, we evaluated the reproductive output from 401 goshawk breeding opportunities on the Kaibab Plateau, Arizona during 1999-2002. Concurrently, we estimated densities of 10 goshawk prey species (seven birds, three mammals) using distance sampling. We then assessed the relationship between goshawk productivity (number of fledglings produced) and prey density within and among years by relating the contribution of individual prey species and total prey density to goshawk productivity. We also estimated the proportion of total diet and biomass for each species that contributed ?3% of all prey items. Total prey density was highly...
We studied first-year movements of Mexican Spotted Owls (Strix occidentalis lucida) during natal dispersal in canyonlands of southern Utah. Thirty-one juvenile Mexican Spotted Owls were captured and radiotracked during 1992-95 to examine behavior and conduct experiments related to the onset of natal dispersal. Juvenile Spotted Owls dispersed from their nest areas during September to October each year, with 85% leaving in September. The onset of movements was sudden and juveniles dispersed in varied directions. The median distance from nest area to last observed location was 25.7 km (range = 1.7-92.3 km). Three of 26 juveniles tracked (11%) were alive after one year, although none were observed with mates. We conducted...
We conducted a survey of spotted owl (Strix occidentalis) ectoparasite richness by examining live and museum specimens of the three subspecies of spotted owl. Seven ectoparasite species from five arthropod orders were collected. A tick (Dermacentor occidentalis), a mite (Euschoengastia sp.), and a flea (Opisodasys vesperalis) were collected, but were presumed to be accidental strays from prey. Strigiphilus lice were found on all the subspecies of spotted owl, while the louse Kurodaia magna was only collected from the northern spotted owl (S. o. caurina). The hippoboscid fly Icosta americana was found on the California spotted owl (S. o. occidentalis); this species had previously been well documented in the northern...
Available information on the status, of the western Burrowing Owl (Athene cunicularia hypugaea) in Arizona is limited. To determine its current status, I sent out questionnaires, made personal contacts, conducted field observations, and searched the literature. These data indicated that relatively little is known in Arizona about this uncommon species. This paper summarizes existing information on the Burrowing Owl in Arizona and provides baseline information for future studies. Location records suggest that this species is a widespread, albeit uncommon, bird in Arizona. The data compiled during this study are still not adequate to assess the status of Burrowing Owls in Arizona as of 1998. An annotated bibliography...