Also confined to the Old World are the Capercaillies (Tetrao), of which four species and a number of hybrids are known. They are large birds, the males being thirty or thirty-five inches long and weighing ten or twelve pounds, while the females are some twelve inches shorter and only weigh four or five pounds. The tail is composed of eighteen feathers, as in the Black Grouse, but it is the middle instead of the outer pair that is longest, thus producing a rounded or slightly wedge-shaped tail. The Capercaillies are inhabitants mainly of coniferous forests, feeding, especially during the winter, on the tender shoots of the pine and spruce, but at other seasons they search for seeds, fruits, grain, etc., often at considerable distance from the woods. The male is polygamous, and at the beginning of the nesting season mounts to the top of some tall tree and utters his loud note, which is a call to the females and a challenge to other males. Should another male approach, a battle is certain, which often lasts until both are bleeding and torn, and so exhausted that they may frequently be captured in the hand. Ordinarily, the male is extremely wary and although so large and heavy flies with little or no noise and very rapidly. The best-known species is the Common Capercaillie (T. urogallus), the male of which is dark gray above, with the wings brown speckled with black, while the chest is lustrous green and the abdomen black with white spots. The female is much barred and spotted with tawny red, black, and white, with the throat and breast reddish and the tail dark reddish brown with black bars. This species is found in the pine forests of Europe and northern and central Asia, being originally also a native of the British Islands, where it was entirely exterminated about the middle of the last century, but was later introduced from Sweden and is now firmly established and abundant in many parts of north Britain and appears to be gradually spreading to new territory. It frequently crosses with the Black Grouse, and the male hybrid is hardly to be distinguished from the Gray-hen except in size. It has also been known to cross with the English Pheasant and the Willow Ptarmigan. The handsomest member of the genus is the Ural Capercaillie (T. uralensis) of the Ural Mountains. It is similar to the last but paler above, with the wings and shoulders light reddish brown and the lower parts mainly white. In northeast Siberia its place is taken by a slender billed species (T. parvirostris), and this is replaced in Kamchatka by another (T. kamchaticus), which is the smallest of the genus.