The Rock Ptarmigan is a hardy medium-sized grouse of the high Arctic and alpine tundra, famous for a remarkable seasonal wardrobe change. In winter it becomes almost pure white to vanish against the snow, and as the season turns it molts into mottled grey and brown so it blends with lichen-covered rock and bare ground. Its legs and even its toes are feathered, acting as natural snowshoes on soft snow.
Rather than migrating away from the cold, Rock Ptarmigan are largely sedentary, toughing out brutal winters on windswept ridges where the wind keeps some vegetation exposed. They are birds of open, treeless country, and across their vast northern range they have adapted to some of the harshest conditions any land bird endures. In several cultures of the far north they are an important game bird and a familiar symbol of the mountains.
Identification depends heavily on the season. In winter both sexes are white apart from black tail feathers, and the male shows a black line running through the eye. In summer the sexes diverge, with males a cold greyish-brown and females a warmer golden-brown, both finely barred and spotted with black and white. The bill is slim and black, and a red comb over the eye is most obvious on displaying males.
| Size | About 34 to 36 cm long; weight roughly 440 to 640 grams |
| Wingspan | Around 54 to 60 cm |
| Winter plumage | Almost entirely white with black tail feathers |
| Male summer | Cold greyish-brown, splotchy, with white wings and belly |
| Female summer | Paler golden-brown, heavily barred black and white |
| Face | Slim black bill, black eye line on males, red eye comb when displaying |
Rock Ptarmigan are not songbirds and their voice is low and guttural. Displaying males give a distinctive dry, rattling, staccato croak, often delivered during a display flight in which the bird flies steeply upward, stalls, then parachutes down with spread tail while calling. The everyday repertoire includes grating groans, belching notes and low clucking sounds between members of a group.
The Rock Ptarmigan has a huge circumpolar range, breeding across Arctic and subarctic Eurasia and North America, including Greenland and Iceland, as well as on high mountains such as the Alps and the Pyrenees where suitable alpine tundra persists further south. It favors rocky mountainsides, high ridges and open tundra above the tree line, and in winter it generally keeps to higher, more barren ground than the related Willow Ptarmigan.
The diet is almost entirely plant-based. In winter Rock Ptarmigan rely heavily on the buds, twigs and catkins of dwarf birch, willow and other hardy shrubs, digging through snow to reach them. In the warmer months they broaden their menu to leaves, flowers, berries and seeds, and newly hatched chicks take insects and other small invertebrates for the protein they need to grow quickly.
The nest is a simple shallow scrape on the ground, lined with a little vegetation and feathers and usually sheltered beside a rock or low plant. The female lays a clutch of around five to nine eggs, buff colored and heavily blotched with brown, and incubates them alone for about three weeks. The downy chicks leave the nest within a day of hatching and feed themselves under the hen's close guard. There is normally a single brood each year.
- Willow Ptarmigan: Larger and stockier with a heavier bill; males lack the black winter eye line
- White-tailed Ptarmigan: Smaller with an all-white tail in every season, unlike the black tail of Rock Ptarmigan
- Ruffed Grouse: A woodland grouse that does not turn white and has a fan-shaped banded tail
Why does the Rock Ptarmigan turn white in winter?
It molts into white plumage as camouflage against snow, helping it hide from predators such as foxes and birds of prey during the long Arctic winter.
How does it survive Arctic winters without migrating?
It stays on windswept ridges where vegetation is exposed, feeds on buds and twigs, and its densely feathered legs and toes act as snowshoes and insulation.
How is it told apart from the Willow Ptarmigan?
The Rock Ptarmigan is slightly smaller and slimmer-billed, males show a black eye line in winter, and it tends to favor higher, more barren ground.
Where can Rock Ptarmigan be found?
They live right around the northern hemisphere in Arctic and alpine tundra, from North America and Greenland across Eurasia, plus mountain ranges like the Alps.