(Lagopus mutus), a bird of the family Tetraonidae, order Galliformes. The rock ptarmigan measures approximately 35 cm in length and weighs 430–880 g. In summer the plumage of males and females is variegated, camouflaging the bird well on the ground. In winter the plumage is white, and the male has a black stripe at the base of the bill.
The rock ptarmigan lives in arid, rolling tundra and the alpine zone of the mountains of Europe, Asia, and North America and also in mountains as far south as the Alps, the Altai, the Khangai, and the mountains of central Japan. In winter it migrates. It nests on the ground. There are up to 12 eggs in a clutch. Only the female broods, for a period of 24–26 days. The adult ptarmigan feeds on seeds, buds, shoots, and berries, while the young feed on insects. The bird has little commercial importance.