Ptarmigans And The Cairngorm Mountains 

Ptarmigans are possibly Britain's toughest birds and live in the cold, harsh mountains of Scotland. In snowy conditions, their feathered feet act as snow shoes, so the ptarmigan can walk even on soft snow.
Ptarmigans are masters of camouflage, changing their colour to suit the season. In winter, they are completely white except for a short black tail, while in summer a brown and yellow plumage blends the ptarmigan into the lichen covered rocks.
This wide-ranging game bird can be found in many of the world's alpine and arctic regions, and they are the only birds in Britain to turn completely white.