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.

cold and snowy boreal w inter (Semenov-Tian-Shansky 1960, Kuzmina 1977, Andreev 1980, Potapov 1985). Five grouse species occur in Pasvik: the Willow Ptarm igan, Rock Ptarm igan, Black G rouse, Capercaillie, and Hazel Grouse. These species differ in their habi­ tats, diet, and foraging behaviour. The Willow Ptarmigan occurs throughout the lowland tundra, forest tundra, and locally in mountain tundra, however it does not occur high in the mountains (Fig. 2.6). In the forest zone it mainly inhabits shores o f rivers, streams and lakes overgrown by willows, on peat bogs, old fire sites and clearing (Semenov-Tian- Shansky 1960, Semenov-Tian-Shansky & Gilyazov 1991). The summer diet o f Willow Ptarmigan includes great bilberry leaves, bo ttle­ brush stems, bilberry shoots, black crowberries and bilberries, less frequently great and red bilberries, cow wheat seeds. Adult birds only infrequently take insects and other invertebrates. Fledglings, on the contrary, in July mainly eat animal food: saw fly larvae, caterpillars and other insects, and spiders. O f the plant food fledglings take the most energy-rich ones, i.e. seeds o f sedge, cow wheat, andromeda, moss sporangia, and mushrooms. In August, berries, parts o f plants and flowers are taken more often than seeds and insects, and in September the diet o f first-autumn birds does not differ greatly from that o f adults. In winter, the birds feed on twigs. On the banks o f rivers and streams they mainly take willow, on the bogs they feed on the Arctic birch, and in the forest, especially at the old fire sites, they eat foot shoots of birches (Semenov-Tian-Shansky 1960, Semenov-Tian-Shansky & Gilyazov 1991). Throughout the year Willow Ptarmigans forage on the ground. In winter, the bird runs from bush to bush on the snow and bites off thin ends o f shoots. In the middle o f the day the birds usually rest on the snow and digest their food. In the L .l. L.m. Figure 2.6. Optimal habitats of Willow Ptarmigan (L.L), Rock Ptarmigan (L.m .), Capercaillie (T.u.), Hazel Grouse (T.b.) and Black Grouse (L.t.) in the Pasvik valley. 91