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1 June 2012 Autumn Migration Ecology of the Northern Saw-Whet Owl (Aegolius acadicus) in Northern Montana
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Characterizing the migration strategies of Northern Saw-whet Owls (Aegolius acadicus) has proved difficult due to variation in movement patterns within and among regions. Such variation underscores the need for information from sites throughout the species' range. To elucidate regional patterns in Northern Saw-whet Owl migration ecology, I studied migration in northern Montana from 2001–06, banding a total of 668 owls between 30 August and 31 October. Capture rates varied greatly among years, as did age ratios. Capture rates peaked between mid-September and early October. Weather variables did not have detectable effects on migration magnitude, but capture rates decreased approximately 2% for every 10% increase in moon illumination. Two owls originally banded in Alberta were captured at my banding site during this study. Additionally, two owls banded during this study were encountered elsewhere: one found dead in southern Montana and the other recaptured in Massachusetts, approximately 3322 km east of my study site. Results were consistent with the hypothesis that high rates of breeding dispersal and density-dependent migratory responses yield annual, latitudinal migrations that vary in magnitude and have a nomadic component.
and Graham G. Frye "Autumn Migration Ecology of the Northern Saw-Whet Owl (Aegolius acadicus) in Northern Montana," Journal of Raptor Research 46(2), (1 June 2012).
Received: 28 March 2011; Accepted: 1 January 2012; Published: 1 June 2012

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