In winter, Rock Ptarmigan are white with dark eyes, bill, lores (area between bill and eye), and tail feathers. Breeding males have scarlet patches (“combs”) above their eyes. They remain white into midsummer, then molt into brown plumage with dark barring and dark tail feathers. The wings and legs remain mostly white. Breeding females are camouflaged with intricate dark and pale brown mottling, with some white in legs and wings.
Walks slowly through tundra, eating plant matter and some insects by browsing or pecking on the ground or in low vegetation. Males perform incredible aerial song displays as well as animated ground displays for females.
Nests in dry, barren, stony areas of tundra and alpine habitats above treeline. Winters in similar habitats as well as in gaps in the boreal forest.
Ornithologists recognize many subspecies around the world. In general, they fall into two broad groups, one that nests in western Europe and northern Scotland (the “muta” group), the other in Asia, Iceland, and North America (the “rupestris” group). The populations that nest the farthest north, and those on the Aleutian and other maritime islands, tend to be the largest and darkest. It’s been suggested that two subspecies should be given full species status: the evermanni subspecies, found on Attu and Agattu in the Aleutian Islands, and welchi, which inhabits western Newfoundland. Because both differ strongly in plumage and size from other Rock Ptarmigan, evermanni and welchi were originally described as full species in the nineteenth century, by ornithologists Daniel Giraud Elliot and William Brewster.