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Comparative ecology of the Flammulated Owl and Northern Saw-whet Owl during fall migration

Journal of Raptor Research

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Abstract

We compared the migration ecology of two owl species that exhibit different migration strategies: the Flammulated Owl (Otus flammeolus) and the Northern Saw-whet Owl (Aegolius acadicus). During fall 1999-2004, we captured 117 Flammulated Owls and 1433 Northern Saw-whet Owls in the southern Boise Mountains of southwestern Idaho. These owl species exhibited contrasting seasonal timing and body condition. Flammulated Owl captures peaked in mid-September and Northern Saw-whet Owl captures peaked in early to mid-October. Flammulated Owls displayed greater body condition than Northern Saw-whet Owls and increasing condition scores during the season, whereas Northern Saw-whet Owls had no apparent seasonal condition patterns. Based on seasonal timing of captures, both species showed unimodal movement patterns characteristic of fall migrants. However, in 1999 both species' capture rates were at least double those in other years of this study. Flammulated Owls' earlier arrival and departure, coupled with superior body condition, were consistent among years and typical of a long-distance migration strategy. In contrast, the Northern Saw-whet Owls' later arrival, more lengthy passage, and variable body condition were more characteristic of a short-distance migrant strategy. Furthermore, Northern Saw-whet Owls' body condition was significantly lower during the irruptive year than during nonirruptive years, supporting the notion that population density affects their migratory condition. ?? 2006 The Raptor Research Foundation, Inc.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Comparative ecology of the Flammulated Owl and Northern Saw-whet Owl during fall migration
Series title:
Journal of Raptor Research
Volume
40
Issue:
2
Year Published:
2006
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Raptor Research
First page:
120
Last page:
129