Males are much bigger than the females. They range from 74 to 85 cm (29 to 35 in) in length with wingspan of 90 to 125 cm (34-49 in) and averaging 4.1 kg. The body feathers are coloured dark grey to dark brown, while the breast feathers are dark metallic green. The belly and undertail coverts vary from black to white depending on race. The hen's body l is 54-64 cm (21-25 in) long, the wingspan is 70 cm (28 in) and weighs 1.5-2.5 kg. Feathers on the upper parts are brown with black and silver barring, on the underside they are more light and buffish-yellow.Both sexes have a white spot on the wing bow. They have feathered legs. Both sexes have a white spot on the wing bow. They have feathered legs, especially in the cold season for protection against cold.
Habitat and Distribution
They breed across northern parts of Europe, western and central Asia in mature conifer forests. At one time it could be found in all the taiga forests of northern and northeastern Eurasia, within the cold temperate latitudes and the coniferous forests. In Norway, Sweden, Finland, Russia and Romania populations are quite big, in the forested areas. When flying they avoid young and dense forests.
They feed on a variety of food types, including buds, leaves, berries, insects, grasses and in the winter mostly conifer needles. They also eat blueberries in season, these darken their faeces, making them formless.
They nest under low branches of a young tree or a broken tree crown. At the beginning of the breeding season the hens are very sensitive towards disturbances and leave the nest quickly. They lay their eggs within 10 days, the average clutch size is eight eggs but may reach 12 eggs. Breeding lasts about 26-28 days according to weather and altitude. The eggs are speckled with brown spots.