Семенов-Тян-Шанский О.И. Экология тетеревиных птиц. Москва, 1959.

EXPLANATIONS FOR ILLUSTRATIONS 1. Timberline on slopes of Tshuna-tundra in winter. 2. Spruce forest with Pleurozium Schreberi, Vaccinium myrtillus and Empetrum nigrum in the floor cover. 3. Pine forest with Cladonia alpestris and Vaccinium myrtillus in the floor cover. 4. The habitat of the Rock ptarmigan on the west slope of Tshuna- tundra. 5. Pine branches, browsed by the Capercaillie in foraging. 6 . An explosion of snow-dust, caused bu the Capercaillie starting from under the snow. 7. Capercaillie female in fly. 8 . Capercaillie male approaching his dust-bath. 9. Capercaillie male dusting. Phot. 8 & 9 are made with a self­ photo-snapshot device, in Petshora-Ylytch Reserve. 10. Capercaillie female of a month age. 11. Capercaillie male of a month age. Phot. 10 and 11 are made on the same day; note the difference in postures, owing to sex. 12. Snow burrow of a Blackgame female. 13. Blackgame males displaying (Petshora-Ylytsh Reserve). 14. Snow burrow of a Hazel Grouse. 15. The tracks of Willow Grouse foraging. 16. Willow Grouse juvenile (Petshora-Ylytsh Reserve). 17. Rock ptarmigans in windy weather (Tshuna-tundra). 18. Rock ptarmigan flying up (Tshuna-tundra). 19. Rock ptarmigan male at spring moulting. 20. Rock ptarmigan juvenile in mixed summer-autumn plumage. 21. Seasonal changes of food composition in Tetrao urogallus (adults above, juveniles below). Explications, from above: winter brow­ sing forage (white); evergreen forage (frequent oblique hatched); summer-green forage (sparse oblique hatched) blossoms (dotted); berries (circles); seeds and capsules (vertical hatched); mosses and mushrooms (oblique hatched); animals (cross hatched); grit (black). 22 . Cottonweed (Eriophorum vaginatum) in bloom. 23. Melampyrum pratense with seeds. 24. Seasonal changes in food composition of Lyrurus tetrix (for explications — see above, fig. 21). 25. Seasonal changes in food composition of Tetrastes bonasia (for explications — see above, fig. 21 ). 26. Alternations in browsing food of Lagopus lagopus, in connetion with snow cover height. 27. Seasonal changes in food composition of Lagopus lagopus (for explications — see above, fig. 21) 28. Bilberry (Vaccinium myrtillus) stalks, browsed by Tetraonids. 29. Crowberry (Empetrum nigrum) with fruits. 30. Seasonal changes in food composition of Lagopus mutus (for explications — see above, fig. 21). 20-3037 305