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 the Russian High Arctic overwinters during the polar night and survives by feeding on rich vegetation on and underneath high cliffs where seabird colonies are located in summer.<ref name="FJL/">Dinets, V. (2001) Winter ecology of Willow Ptarmigan "Lagopus lagopus" and Rock Ptarmigan "L. mutus" at the northern limit of their range. "Ornitologia" 29: 326-327 (in Russian with English summary).</ref> During the last ice age, the species was far more widespread in continental Europe. The rock ptarmigan feeds primarily on birch and willow buds and catkins when available. It also eats various seeds, leaves, flowers, and berries of other plant species. Insects