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.

sometimes with unripe cones, jun ip er needle, and berries (Sem enov -T ian-Shansky 1960, Semenov-T ian-Shansky & Gilyazov 1991). In summer, Capercaillies forage on the ground, and in w inter, m ainly on pine trees. In winter, females spend much time in the trees. Males also spend tim e in the trees, but often forage on the snow, eating young pine shoots o r ju n ip ers (Semenov- Tian-Shansky 1960, Sem enov-T ian-Shansky & Gilyazov 1991). Hazel Grouse inhabits the most productive patches o f birch and mixed pine and birch forests, manly in the stream valleys where low alders, birches, and willows grow. These birds avoid open habitats: bogs, bu rn t areas, and especially the m o u n ­ tain tund ra (Fig. 2.6). In summer, Hazel G rouse m ainly forage on the ground. They take leaves, dry fruits and seeds o f sedge, c ra n e ’s bill, cow -w heat, birch. Fledglings eat berries, seeds, and invertebrates. In winter, Hazel G rouse take catkins, buds and shoots or birch, alder, rowan, bird cherry. They no t only sleep u n d e r th e snow, but also take green bilberry shoots to supplem ent th e ir diet (Sem enov -T ian -Shan sky 1960, Kirikov 1975, Potapov 1985, Sem enov-T ian-Shansky & G ilyazov 1991). Structure of the ecological niche of grouse The co-existence o f several grouse species in Pasvik is facilitated by the fact th a t they occupy different ecological n ich es and th u s avoid com p e titio n . Differences in the structure o f the ecological niche m ainly co n ce rn diet, habitats and foraging behaviour o f the birds. In summer, all grouse species have sim ilar lifestyle. They forage on the ground, eat leaves, flowers, berries, and seeds o f h e rb a­ ceous plants and subshrubs, and various invertebrates. D uring this period, the e co ­ logical niches o f different species overlap broadly. Ecological segregation o f grouse species is most app a ren t in w in ter when they start to take twigs. Their w inter diets differ markedly. Capercaillies m ainly take pine needles. The Black G rouse eats birch catkins, buds, and shoots. T he Hazel G rouse forages on catkins, buds and shoots o f birch, alder and o th e r deciduous trees. The Willow Ptarm igan eats the apical shoots o f willows and A rctic b irch, Rock Ptarm igan takes shoots, buds and berries o f evergreen subshrubs, saxifrage, A rctic birch. D ifferences in diet govern the species-specific spatial distribu tion . The Capercaillie lives in pine forest, Black and Hazel G rou se in m ixed pine and birch wood. The Willow Ptarm igan inhabits bogs, low land tu n d ra and lower slopes o f the m ountains, whereas the Rock Ptarm igan occurs in m oun tain tund ra. Species-specific characteristics o f foraging and hab itat use suggest a certain ecological differentiation between the species. However, th ese p aram eters overlap broadly and do not allow us to characterise th e ecological n ich e o f each species. For example, the Capercaillie is known to o ccu r not only in con iferou s, but also in 94