The willow ptarmigan was designated the official state bird of Alaska in 1955. There are three kinds of ptarmigan and all can be found in Alaska - the willow ptarmigan and rock ptarmigan (which are also found in Scandinavia, Russia, and northern Eurasia), and white-tailed ptarmigan (found only in North America). The famous red grouse of Scotland is a race of the willow ptarmigan.

Ptarmigan are arctic grouse. The willow ptarmigan (Lagopus lagopus) changes color from light brown in summer to snow white in winter for effective camouflage from predators. Another distinctive feature is its feathered toes. In winter months the willow ptarmigan eats mosses and lichens, willow buds and twigs, a little birch; seeds and berries when available. In summer their diet expands to vegetable matter and occasionally caterpillars or beetles.

Ptarmigan are sociable in winter and usually feed and roost in the snow close together. In spring flocks of several thousand sometimes appear en route to their breeding grounds. These huge flocks rapidly disperse as summer areas are reached and cocks demand elbow room for their share of the tundra.

Source:

Ptarmigan - Wildlife Notebook: Alaska Dept. of Fish & Game
Willow Ptarmigan - borealforest.org

Links:

Willow Ptarmigan: (sound file) eNature - Nat. Wildlife Fed.
Willow Ptarmigan - Lagopus lagopus: USGS
State Birds 50 states List
National Bird