On the other hand, the second class consists of those birds which are exposed to the hostility of many wild animals, and more especially of man. These kinds, typified by the red grouse, partridges, quails, and guinea-fowls, are generally dingy in hue, with a tendency to pepper-and-salt in their plumage; and they usually display very little difference between the sexes, both cocks and hens being coloured and feathered much alike. In short, they are protectively designed, while the first class are attractive. Their plumage resembles as nearly as possible the ground on which they sit or the covert in which they skulk. They are thus enabled to escape the notice of their natural enemies, the birds of prey, from whose ravages they suffer far more in a state of nature than from any other cause. We may take the ptarmigans as the most typical example of this class of birds; for in summer their zigzagged black-and-brown attire harmonises admirably with the patches of faded heath and soil upon the mountain-side, as every sportsman well knows; while in the winter their pure white plumage can scarcely be distinguished from the snow in which they lie huddled and crouching during the colder months. Even in the brilliant species, Mr. Darwin and Mr. Wallace have pointed out that the ornamental colours and crest are never handed down to female descendants when the habits of nesting are such that the mothers would be exposed to danger by their conspicuousness during incubation. Speaking broadly, only those female birds which build in hollow trees or make covered nests have bright hues at all equal to those of the males. A female bird nesting in the open would be cut off if it showed any tendency to reproduce the brilliant colouring of its male relations.