The Rock Ptarmigan is the "Snow Chicken" of the polar regions ("chicken" in that they are trusting). These "chickens" are truly adapted to their environment in that they turn white in the winter (white feathers are hollow and are therefore warmer), they sleep under the surface of the snow at night for warmth, their legs and feet are feathered to retain heat, and special adaptations on their feet help them walk on snow. They are a marvel of environmental adaptation.