WINTER HABITAT SEGREGATION IN THE SEXUALLY DIMORPHIC BLACK-BILLED CAPERCAILLIE TETRAO-UROGALLOIDES

Black-billed Capercaillie show distinct dimorphism in size and colour and conspicuous sexual differences in winter survival strategies, even though both sexes feed on buds and twigs of larch. The heavier cocks create and maintain "gardens" of dwarf larch trees, perhaps because in habitats dominated by sparse larch forests on permafrost there are few larch trees large enough to support their weight. The "gardens" provide more food and allow the cocks to save time and energy during foraging. Hens tend to overwinter in flocks higher in the mountains, to stay in younger and denser larch forests, and to use less productive habitat. The lighter hens are able to get adequate food in larch trees and perhaps avoid the "gardens" in order to diminish the risk of predation.