La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	The numerical response of breeding Northern Saw-whet Owls Aegolius acadicus suggests nomadism
Auteurs :	Jeff Bowman, Auteur ; Debbie S. Badzinski, Auteur ; Ronald J. Brooks, Auteur
Type de document :	Article
Dans :	Journal of Ornithology (151(2) APR 2010)
Article en page(s) :	499-506
Langues:	Anglais
Résumé :	We used a 13-year time series of abundance estimates of breeding Northern Saw-whet Owls (Aegolius acadicus), and of small mammals from central Ontario, Canada, to assess the numerical response of the owls to small-mammal prey species. We found that the finite rate of increase of breeding owls was directly related to estimates of red-backed vole (Myodes gapperi) abundance. Thus, it appeared that the owls were nomadic, and made decisions about where to breed based on vole supply. The owls showed a much weaker response to deer mouse (Peromyscus maniculatus) abundance. Across all years, 55% of variation in owl rate of increase could be uniquely attributed to vole abundance, whereas only 3% could be attributed to mouse abundance. Consistent with the model of nomadism, there was only a weak relationship between the proportion of hatch-year owls caught at fall banding stations, and small-mammal abundance. Instead, it appeared that Northern Saw-whet Owls avoided years of widespread reproductive failure through the nomadic strategy of selecting breeding sites based on vole supply.

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