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Spring and Winter Home Ranges of the Haida Gwaii Northern Saw-Whet Owl (Aegolius acadicus brooksi)

Waterhouse, F. Louise, Doyle, Frank I., Turney, Laurence, Wijdeven, Berry, Todd, Melissa, Bergman, Carita, Vennesland, Ross G.
The Journal of raptor research 2017 v.51 no.2 pp. 153-164
Aegolius acadicus, adults, females, foraging, forests, habitats, home range, juveniles, landscapes, males, planning, radio telemetry, roosting behavior, spring, surveys, winter
Using radiotelemetry we determined for a managed landscape, seasonal home-range sizes and habitat compositions of the threatened Haida Gwaii subspecies of the Northern Saw-whet Owl (Aegolius acadicus brooksi). We trapped 17 owls, and successfully monitored seven: four adult males from May−June 2011 (spring) and three owls (adult male, juvenile male, juvenile female) from January−February 2012 (winter). The adult males in spring moved up to 2.9 km in a 24-hr survey period and had nonoverlapping 95% fixed kernel home ranges (276−375 ha) that were composed of four defined habitat classes (open, early seral forest, mid-seral forest, older forest). Comparisons between internal core-use areas (50% and 30% fixed kernels) and the larger surrounding 95% fixed kernel home ranges suggested these males used foraging and roosting habitat proportional to its availability within the home ranges. The three tagged winter owls had larger 95% fixed kernel home ranges (690−1310 ha) than those in spring, and moved up to 4.4 km in a 24-hr survey period. Winter home ranges overlapped (14.7−78.4%) and included the four habitat classes. Roosts in spring and winter were confirmed in all but open habitat types. Although our findings suggest that spring and winter home ranges can be composed of a diverse mixture of habitat types, consistent with studies of the subspecies A. a. acadicus, differences in home-range size suggest possible differences in the two subspecies' ecology. Our findings will inform recovery planning for brooksi in managed landscapes.