Insulating snow
The willow grouse stays in its burrow through the night and in the middle of the day. It comes out to graze only for two hours at dawn, and four hours before nightfall. It ruffles up its feathers to increase the insulating effect of its plumage.
Energy-efficient
The burrow is warmed by the willow grouse's body heat, and can maintain a temperature of minus 5°C even when the temperature outside is minus 30°. This makes it possible to reduce by almost half the amount of energy needed to maintain body temperature.
