Responses of Great Horned Owls (Bubo virginianus), Barred Owls (Strix varia), and Northern Saw-whet Owls (Aegolius acadicus) to forest cover and configuration in an agricultural landscape in Alberta, Canada

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Abstract:

Studies on the effects of forest fragmentation on birds have focussed primarily on passerines, with few studies on owls. We assessed the influence of forest amount and configuration on the abundance and distribution of three species of forest owls, Great Horned Owl (Bubo virginianus (Gmelin, 1788)), Barred Owl (Strix varia Barton, 1799), and Northern Saw-whet Owl (Aegolius acadicus (Gmelin, 1788)), in agricultural landscapes with varying amounts of forest cover in central Alberta, Canada. All three species were positively associated with forest cover: Barred Owls were most prevalent in landscapes with >66% forest cover, Great Horned Owls in landscapes with between 36% and 65% forest cover, and Northern Saw-whet Owls in landscapes with between 16% and 100% forest cover. Regression models containing configuration variables were chosen as best models using AIC for all three species. Great Horned Owls were most abundant in landscapes with high heterogeneity: more forest-nonforest edges and higher forest patch area variation. Barred Owls were more likely to occur in landscapes with larger forest patch areas and Northern Saw-whet Owls were more abundant in landscapes that were more connected. These relationships are consistent with predictions based on body size of owls and local habitat relationships described in the literature.

Les études des effets de la fragmentation des forêts sur les oiseaux se sont intéressées principalement aux passereaux, avec peu de travaux sur les hiboux. Nous évaluons l’influence de l’étendue et de la configuration de la forêt sur l’abondance et la répartition de trois espèces forestières de hiboux, le grand-duc d’Amérique (Bubo virginianus (Gmelin, 1788)), la chouette rayée (Strix varia Barton, 1799) et la petite nyctale (Aegolius acadicus (Gmelin, 1788)), dans des paysages agricoles possédant des étendues diverses de couverture forestière dans le centre de l’Alberta, Canada. Il existe une association positive entre les trois espèces et le couvert forestier : les chouettes rayées prédominent surtout dans les paysages qui présentent plus de 66 % de forêt, les grands-ducs d’Amérique dans les paysages à 36 % - 65 % de forêt et les petites nyctales dans les paysages à 16 % - 100 % de forêt. Nous avons choisi pour les trois espèces les meilleurs modèles de régression contenant les variables de configuration à l’aide du critère AIC. Les grands-ducs d’Amérique sont plus abondants dans les paysages de forte hétérogénéité avec plus de lisières forêt et non forêt et une variation plus grande des taches forestières. Les chouettes rayées ont plus de chances de se retrouver dans les paysages contenant des taches forestières plus étendues et les petites nyctales sont plus abondantes dans les paysages qui sont plus interconnectés. Ces relations s’accordent avec les prédictions basées sur la taille corporelle des hiboux et des relations d’habitat décrites dans la littérature.

Document Type: Research Article

Publication date: October 1, 2008

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  • Published since 1929, this monthly journal reports on primary research contributed by respected international scientists in the broad field of zoology, including behaviour, biochemistry and physiology, developmental biology, ecology, genetics, morphology and ultrastructure, parasitology and pathology, and systematics and evolution. It also invites experts to submit review articles on topics of current interest.
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