The Owl Invasion of Amherst Island, Ontario, January-April 1979
DISTRIBUTION The owl invasion of Amherst Island, Ontario, January-April 1979 A report from the owl capital of the world of the parliament of winter, 19 79 Gary P. Bell, Frank J. S. Phelan and Ron C. P. Wypkema. Photographsby the authors. LTHOUGHNORTHERN OWLS moved into easternNorth America in large Short-eared Owl on Amherst Island. Photo/ numbers in the winter of 1978-79, the Frank J. S. Phelan. invasionof owls in the Kingston, Ontar- io, Canada area was unique. Over the course of the winter, thousands of bird- watchers from across Canada and the United States visited Amherst Island. 3 miles southwestof Kingston. to view an unusualassemblage of owl species. Amherst Island is an isolated rural community lying 2 miles south of the north shore of Lake Ontario, at 44ø10'N, 76ø40'W.The 25-squaremile islandpro- vides a variety of habitats including active farmland, old field pasture, woods and marsh. During the latter part of 1978the pop- ulation densityof meadowvoles (Micro- tus penns.vlvanicus) became very high. Great Gray Owl on Amherst Island. Photo/ The isolation of the island, and the lack Gary P. Be!!. of terrestrial predators such as foxes intensifiesthe natural population cycles Saw-whet Owl on Amherst Island. Photo/ of small mammals. Extreme population Frank J..S. Phelan. "outbreaks", then, are regular occur- rences.Large incursionsof raptorshave long been associatedwith such out- breaks of voles, and periodically raptor densities on Amherst Island and Wolfe Island, 2 miles to the east, increase dramatically in responseto abundances of meadow voles (Phelan. 1976; Phelan and Robertson,1978). These raptor den- sity increasesare easily predicted, but along with this increasein numbers of raptors, comes a highly unpredictable increasein the numbers and diversity of raptor species.
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