BLACKCOCK (Tetrao tetrix)  , the English name given to a bird of the family Tetraonidae or grouse, the female of which is known as the grey hen and the young as poults . In size and plumage the two sexes offer a striking contrast, the male weighing about 4 lb, its plumage for the most part of a rich glossy black shot with blue and purple, the lateral tail feathers curved outwards so as to form, when raised, a fan-like crescent, and the eyebrows destitute of feathers and of a bright vermilion red . The female, on the other hand, weighs only 2 lb, its plumage is of a russet brown colour irregularly barred with black, and its tail feathers are but slightly forked . The males are polygamous, and during autumn and winter associate together, feeding in flocks apart from the females; but with the approach of spring they separate, each selecting a locality for itself, from which it drives off all intruders, and where morning and evening it seeks to attract the other sex by a display of its beautiful plumage, which at this season attains its greatest perfection, and by a peculiar cry, which Selby describes as " a crowing note, and another similar to the noise made by the whetting of a scythe." The nest, composed of a few stalks of grass, is built on the ground, usually Blackcock . beneath the shadow of a low bush or a tuft of tall grass, and here the female lays from six to -ten eggs of a dirty-yellow colour speckled with dark brown . The blackcock then rejoins his male associates, and the female is left to perform the labours of hatching and rearing her young brood . The plumage of both sexes is at first like that of the female, but after moulting the young males gradually assume the more brilliant plumage of their sex . There are also many cases on record, and specimens may be seen in the principal museums, of old female birds assuming, to a greater or less extent, the plumage of the male . The blackcock is very generally distributed over the highland districts of northern and central Europe, and in some parts of Asia . It is found on the principal heaths in the south of England, but is specially abundant in the Highlands of Scotland .