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1 September 2009 Northern Saw-Whet Owl (Aegolius acadicus) Autumn Migration Magnitude and Demographics in South-Central Indiana
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Abstract

Three banding stations were located in south-central Indiana (2002–07) to study migration patterns of Northern Saw-whet Owls (Aegolius acadicus). Saw-whet owl captures ranged from 59 in 2002 (1 station) to 447 in 2007 (3 stations), with 2007 an irruption year in at least one location. The proportion of hatch-year owls was 54.8% on average, but lower in 2004 (30.9%). Hatch-year owls consistently arrived 4–5 d earlier than older saw-whet owls in south-central Indiana. We used morphometric sexing techniques to classify 80% of the saw-whet owls we captured as females, and 7% as males. Encounters of birds banded at other stations indicated that most owls captured in south-central Indiana in fall had migrated around the west side of the Great Lakes. The irruption of 2007 was likely due to a large influx of saw-whet owls moving through the Ohio River Valley from eastern regions. Greatest numbers of saw-whet owl captures were associated with clear nights and relatively calm west-to-northwest winds after the passage of a cold front. For owls captured at our station and another, we calculated the average migration rate of 28.8 ± 15.8 km/d (N  =  9).

Ross A. Brittain, Vicky J. Meretsky, Jess A. Gwinn, Jeffrey G. Hammond, and Jeffery K. Riegel "Northern Saw-Whet Owl (Aegolius acadicus) Autumn Migration Magnitude and Demographics in South-Central Indiana," Journal of Raptor Research 43(3), 199-209, (1 September 2009). https://doi.org/10.3356/JRR-08-51.1
Received: 17 July 2008; Accepted: 1 April 2009; Published: 1 September 2009
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