Ardea
Official journal of the Netherlands Ornithologists' Union

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Artuso C. (2009) Breeding and population density of the Eastern Screech Owl Megascops asio at the northern periphery of its range. ARDEA 97 (4): 525-533
Random-stratified spring nocturnal surveys using tape playback were conducted for Eastern Screech Owls Megascops asio from 2004 through 2007 in Winnipeg, Manitoba, Canada, at the northern periphery of its range. Surveys were stratified by (1) human density, (2) riparian vs. non-riparian habitat, and 3) the presence or absence of suburban greenspace. A total of 120 transects (each 1.75 km long) were surveyed, with 55 Eastern Screech Owls detected. Eastern Screech Owl densities peaked in moderate to high-density suburban areas (>20 persons/ha), where 36 (66%) detections occurred, and were lowest in wildlands (<1 pair/ha), where no detections occurred. Fifty-one (93%) Eastern Screech Owls were detected in riparian areas. Only 20 (36%) Eastern Screech Owls were detected in suburban greenspaces. In 4 years I located a total of 46 successful Eastern Screech Owl nests, 6 failed nests, and 37 territories with non-breeding owls. Excluding repeat cavity uses, a total of 61 nest sites and territory centres were located, of which 38 (62%) were in natural cavities, 21 (34%) in nest boxes, and 2 (3%) at sites where cavity choice was undetermined. Fledging dates ranged from 28 May 3 July (mean 15 June, SE 1.4) over the 4-year period. Eastern Screech Owls showed larger average brood sizes and earlier average fledging dates in moderate and high-density suburban areas than in low-density suburban and rural areas.


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