White-tailed ptarmigan and development of the chicks. This suggests that the hens' food calls assist in enhancing survival rates of juvenile ptarmigans. The young birds remain with their mother throughout the summer and autumn season. The white-tailed ptarmigan is well-camouflaged when on the ground. In his pioneering 1909 book on the subject, "Concealing-Coloration in the Animal Kingdom", the American artist Abbott Thayer wrote: The white-tailed ptarmigan has feathers located on its feet to serve as protection from the extreme cold often experienced in the alpine tundra environment. In addition, these birds have feathers around their nostrils to warm the air prior to
Rock ptarmigan ptarmigan by about 10%. The male's "song" is a loud croaking. The rock ptarmigan is seasonally camouflaged; its feathers moult from white in winter to brown in spring or summer. The breeding male has greyish upper parts with white wings and under parts. In winter, its plumage becomes completely white except for the black tail. It can be distinguished from the winter willow ptarmigan by habitat—the rock ptarmigan prefers higher elevations and more barren habitat; it is also smaller with a more delicate bill. The rock ptarmigan is a sedentary species which breeds across arctic and subarctic Eurasia and North