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

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.