The birds of Pasvik / E. I. Khlebosolov, O. A. Makarova, O. A. Khlebosolova [et al. ; English transl. Nikita Chernetsov]. - Ryazan : Golosgubernii, 2007. - 175 с. : ил., портр.

T.u., d* T .u.,¥ L.t. Figure 2.7. Structure o f the habitats preferred by male (T.u., t f ) and female (T.u., !j! ) Capercaillies, Black Grouse (L.t.), Hazel Grouse (T.b.), Willow Ptarmigan (L.L) and Rock Ptarmigan (L.m.). deciduous forest. The Black G rouse often takes autumn pine cones and jun iper needles, apart from deciduous trees. Diets o f Black and Hazel G rouse, and their spatial distribution, may be very similar (Semenov-Tian-Shansky 1960, Kirikov 1975, Kuzm ina 1977, Potapov 1985). The most important differences in the structure o f the ecological niche proba­ bly concern specific features o f foraging behaviour and the related morphological features o f the grouse species. Differences in foraging behaviour are most apparent in the methods o f fixing the body on the substrate when feeding. Morphological dif­ ferences are related to the body size, absolute and relative size o f the bill, and pelvic arch (Semenov-Tian-Shansky 1960, Kuzm ina 1977, Potapov 1985). Differences in foraging techniques and morphology, in their turn, dictate the selection o f certain feeding trees and habitats. In w inter the Capercaillie, Black and Hazel Grouse mainly forage in the trees. These three species differ in body size and thus forage in different parts o f the crown or in trees o f different size and age (Fig. 2.7). The Capercaillie is the largest species; therefore it can only feed in the central part o f the crown on thick branches. The most suitable feeding tree for this species is pine. The distance between pine branches is rather large, but large size allows Capercaillies to get needles and twigs at a considerable distance. Males and females in w inter prefer different habitats. Large males feed in the crowns o f tall old trees. Besides, they often forage on the ground where large size allows them to take n e e­ dles o f young pines and junipers. Females are smaller and prefer to stay in m iddle- aged and mature pine forests. The distance between the branches here is smaller than in the crowns o f old trees. This allows the birds to forage successfully (Fig. 2.7, Semenov-Tian-Shansky 1960, Andreev 1979, 1980, Tarkhov 1988). 95