The Capercaillie bird (male) is a huge beast of a game bird, with blackish-slate overall plumage, a big head, shaggy throat and a big, broad black tail that it cocks and spreads turkey-like when displaying. The wing coverts are dark brown and there is a glossy green sheen to the breast. A white patch at the base of the forewing is visible, as is a patch of red skin above the eye, plus it has a pale bill and feathered legs. The Capercaillie bird (female) is a third smaller, brown in colour, and finely marked and patterned with blackish and pale bars and scalloping and with an orangey throat and upper breast which distinguish it from the similar female Black Grouse. The tail is more rufous and longer than in that species.
Capercaillie bird is found in mature coniferous woodland, especially where there is a mixture of spruce, aspen and birch with plenty of shrubby undergrowth. It feeds on buds, leaves and berries in summer and pine needles in winter, when it can occasionally be found in more open terrain. It is sedentary, becoming extinct in Britain in the eighteenth century but reintroduced to Scotland in the 1800s.
The Capercaillie bird (male) has a very unusual-sounding display call, a series of notes lasting 5-7 seconds and commencing with some clicking or knocking sounds, accelerating to a 'pop' like a cork popping, followed by rasping hissing noises like the grinding of a knife-sharpener, occasionally followed by a noisy wing-whirr. A version of this can be described as "ka'ko'ka'ko' uk'k'k'kr'r'r'r'r'r", the latter part in a descending roll. This remarkable sound is uttered in spring in dawn displays by singles or in lekking groups of males, from a tree or on the ground. Other calls given by the Capercaillie bird (male) include a belching "ogh'ogh'ogh'ogh'ghr", and some low bubbling sounds. Females give a Pheasant-like "kock-kock" sound, often in the lekking season. Very noisy inflight when flushed.