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Charlo, MT, United States

Booms T.L.,Alaska Department of Fish and Game | Holroyd G.L.,Environment Canada | Gahbauer M.A.,Migration Research Foundation | Trefry H.E.,Natural Resources Canada | And 7 more authors.
Journal of Wildlife Management | Year: 2014

The North American Breeding Bird Survey, Christmas Bird Count, and regional and national conservation assessments provide convincing evidence that the short-eared owl (Asio flammeus) is experiencing a range-wide, long-term decline in abundance in North America. However, the species has received little conservation or research attention. The short-eared owl is vulnerable to decline because it relies heavily on large, intact grasslands and a specialized diet of unpredictable small mammal prey. The species' nomadic movements compound these vulnerabilities by making a decline difficult to detect with current monitoring programs while obfuscating stewardship responsibilities for managers. The primary threat to the species is loss, fragmentation, and degradation of large tracts of native grasslands and wetlands. We propose the following conservation priorities to better understand and begin addressing the short-eared owl's decline: 1) better define and protect important habitats; 2) improve population monitoring; 3) determine seasonal and annual movements; 4) re-evaluate NatureServe's short-eared owl national conservation classifications; 5) develop management plans and tools; and 6) classify raptors, including short-eared owls, as migratory birds in Canada. We contend that the short-eared owl's need for habitat conservation at large spatial scales, status as a predator, and high reproductive potential that affords the species capacity to recover, make it an effective and useful candidate as an umbrella species for grassland conservation. © 2014 The Wildlife Society.

Seidensticker M.T.,Owl Research Institute | Holt D.W.,Owl Research Institute | Detienne J.,Owl Research Institute | Talbot S.,U.S. Geological Survey | Gray K.,California State University, Chico
Journal of Raptor Research | Year: 2011

We predicted sex of 140 Snowy Owl (Bubo scandiacus) nestlings out of 34 nests at our Barrow, Alaska, study area to develop a technique for sexing these owls in the field. We primarily sexed young, flightless owls (3844 d old) by quantifying plumage markings on the remiges and tail, predicting sex, and collecting blood samples to test our field predictions using molecular sexing techniques. We categorized and quantified three different plumage markings: two types of bars (defined as markings that touch the rachis) and spots (defined as markings that do not touch the rachis). We predicted sex in the field assuming that males had more spots than bars and females more bars than spots on the remiges and rectrices. Molecular data indicated that we correctly sexed 100% of the nestlings. We modeled the data using random forests and classification trees. Both models indicated that the number and type of markings on the secondary feathers were the most important in classifying nestling sex. The statistical models verified our initial qualitative prediction that males have more spots than bars and females more bars than spots on flight feathers P6P10 for both wings and tail feathers T1 and T2. This study provides researchers with an easily replicable and highly accurate method for sexing young Snowy Owls in the field, which should aid further studies of sex-ratios and sex-related variation in behavior and growth of this circumpolar owl species. © 2011 The Raptor Research Foundation, Inc.

Holt D.W.,Owl Research Institute | Gray K.,California State University, Chico | Maples M.T.,Owl Research Institute | Korte M.A.,Owl Research Institute
Journal of Raptor Research | Year: 2016

In 1993 and 1995, we detailed body mass growth rates, plumage development, and related behaviors of Snowy Owl (Bubo scandiacus) nestlings from Barrow, Alaska. We recorded data from 71 of 80 nestlings from 14 of 20 nests in 1993 and 154 of 161 nestlings from 33 of 54 nests in 1995. Only nestlings for which we had data from hatching to at least 25 d of age were included in the growth model. Nestlings hatched between 1-3 d after "pipping" (creating a hole in) the eggshell. The semi-altricial young were covered in white protoptile (first) down plumage at hatching and weighed about 44-45 g. For about the first 7 d, their eyes were closed and movement was limited; the nestlings were dependent on the female for thermoregulation, food, and protection. Growth was rapid and by 8-9 d, the dark gray mesoptile (second) down had begun replacing protoptile down. By about 9-11 d, eyes were open, and by about 14 d, the owls were dark gray in color, and primary flight feather quills emerged. Mass gains were greatest the week prior to pre-fledging nest departure. The owls gained about 56 g every d, between 16-22 d. Around 21 d, the primary flight feathers erupted from their quills, and at approximately 25 d, tail (rectrices) feather quills erupted. After pre-fledging nest departure at approximately 21 d, the young owls roamed the tundra on foot and were fed and protected by both parents. We did not observe voluntary brood reduction; however, some young died in nests. Mass growth slowed substantially by about 34 d, while plumage development, particularly flight feather growth, increased rapidly. Young within and between nests, and years, grew at similar rates. Around 36-43 d, the young began their first attempts at flying, by hopping and pumping their wings. Also at this age, differences in plumage between presumed males and females were noticeable. Between 44 and 55 d, the young fledged, coinciding with the time when primary flight feather P8 reached 16.5 cm, and tail feather T1 reached 11.0 cm. © 2016 The Raptor Research Foundation, Inc.

Holt D.W.,Owl Research Institute | Mull M.L.,P.O Box 673 | Seidensticker M.T.,Owl Research Institute | Larson M.D.,Owl Research Institute
Journal of Raptor Research | Year: 2016

Most species of owls lack distinctive sexual color dimorphism, and plumage is not considered reliable for distinguishing sex. In North America, Long-eared Owls Asio otus are generally considered monomorphic in color, although there are subtle color differences between the sexes. From 1987 to 2015, we investigated differences in plumage coloration of male and female Long-eared Owls in western Montana. We initially used an observational method 1987-1993, followed by a quantitative method 1994-1999, and then a simplified method 2000-2015. When we used the observational method, we correctly sexed all 22 Long-eared Owls. For the quantitative method, we used a Munsell Soil Color Chart to score underwing coverts, tarsometatarsus, and facial disc of breeding males and females and museum specimens purportedly sexed correctly. We found significant sex-specific color differences: underwing coverts G = 136.77, df = 5, P < 0.01, tarsometatarsus G = 44.50, df = 4, P < 0.01, and facial disc G = 50.62, df = 7, P < 0.01. Underwing coverts differed the most between sexes. Based on these plumage color differences, we then correctly sexed all 19 owls captured during fall and winter and later recaptured as breeding birds. Using the simplified method, we correctly predicted the sex of 55 of 58 93% owls captured during fall and winter and later recaptured as breeders. Overall, we correctly predicted sex of 96 of 99 96.9% Long-eared Owls in Montana. We suggest that plumage coloration differences should be investigated in other study areas outside of Montana. © 2016 The Raptor Research Foundation, Inc.

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