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Abstract

The Hudson Bay Lowlands of northern Ontario (comprising tundra and taiga) provide winter habitats for Willow Ptarmigan and Sharp-tailed Grouse as well as Rock Ptarmigan that occasionally fly in from arctic and subarctic regions. Winter food niche segregation/overlap was measured among these three species to investigate potential feeding competition; tamarack and berries were quantified by number and mass in the crops of grouse collected from the vicinity of the former community of Winisk, Ontario (now Peawanuck). All grouse species fed on birch and it was the principal food for Sharp-tailed Grouse. Willow was eaten primarily by Willow and Rock Ptarmigan. The proportions of ingested willow and birch parts differed greatly (P< 0.001) among the three grouse species but food niche overlap did exist among all three. Morisita's Index of food niche overlap, based on numbers of ingested items, was least (0.452/1.0) for Willow Ptarmigan and Sharp-tailed Grouse, intermediate (0.669/1.0) for Willow and Rock Ptarmigan, high (0.957./1.0) for Sharp-tailed Grouse and Rock Ptarmigan, and greatest (0.996/1.0) for Sharp-tailed Grouse at Peawanuck and Moosonee. Resident Willow Ptarmigan and Sharp-tailed Grouse may be segregated partially by habitat. Irruption of Rock Ptarmigan occurs irregularly across years, thus lowering feeding competition for birch parts with Sharp-tailed Grouse, and willow parts with Willow Ptarmigan.

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