The Willow Ptarmigan (Lagopus lagopus), Willow Grouse or in the British Isles the Red Grouse, is a bird of the grouse subfamily. It is a sedentary species, breeding in birch and other forests and moorlands in the tundra of Scandinavia, Siberia, Alaska, northern Canada, in particular the province of Newfoundland and Labrador. It is the state bird of Alaska.
In summer male's plumage is marbled brown, with a reddish hue to the neck and breast, a black tail, and white wings and underparts. It has two inconspicuous wattles above the eyes, which become prominent in the breeding season. The female is similar, but lacks the wattles and has brown feathers strewn all over the belly. In winter, both sexes' plumages become completely white, except for the black tail.
They can be distinguished from the Rock Ptarmigan (L. muta) by habitat (L. lagopus is not found above the tree line), larger size and thicker bill; the summer plumage is browner, the winter Willow Ptarmigan's male lacks the black loral stripe. It is a little bigger than the rock ptarmigan.
The distinctive British Isles subspecies L. l. scotica (Red Grouse) was once considered a separate true British species but is now classified as a sub-species. This moorland bird is reddish brown all over, except the white feet and is common across the north and west of Great Britain and in localised areas on Ireland.
The male's call is a loud go-back go-back.