ENCOUNTERS OF NORTHERN SAW-WHET OWLS (AEGOLIUS ACADICUS) FROM BANDING STATIONS IN ALBERTA AND SASKATCHEWAN, CANADA

摘要

Researchers banded 44:39 Northern Saw-whet Owls (Aegolius acadicus) during autumn at 10 migration-monitoring stations between 2002 and 2007 in Alberta and Saskatchewan, Canada. Sixty-one recaptures of live birds or recoveries of dead birds (together termed "encounters") banded at these stations and recaptures at these stations of birds banded elsewhere occurred during this period. The farthest. saw-whet owl encountered was 2315 km from the banding station (Last Mountain Lake, Saskatchewan, to Hebron, Pennsylvania). Almost half of the encounter locations were east or southeast of the associated banding site. The overall average speed of within-season travel was 37 kmight; however, the average speed of eastward movements was 81 kmight (n = 9). Of 19 within-season (mid-August to mid-December) encounters, hatch-year females en = 11) travelled farther (615 km +/- 464.9) than after-hatch-year females (n = 5; 110 km +/- 33.6; P = 0.047). Three owls apparently overwintered in Alberta and Saskatchewan. During the nonbreeding season, saw-whet owls in Alberta and Saskatchewan may employ more than one movement strategy, including migration, overwintering in the region, and possible nomadism, which suggests that the species is a variable partial migrant. Birds banded at Alberta stations had more southward encounters than those banded at Saskatchewan stations, which were encountered mostly to the southeast, suggesting that autumn movements of saw-whet, owl are influenced by the presence of suitable forested habitat.