Both the eggs and plumage of game birds offer interesting instances of this adaptation. The pencilled plumage of the snipe lying still in the brown marshes it is impossible to detect, although the birds get up at one's feet everywhere. The same may be said of the woodcock in the leaf-strewn woods, and of the nests and eggs of both species. The eggs of the wild-duck assimilate to the colour of the green reeds, and those of the lapwing to the ploughed field or the upland. The colour of the red grouse conforms very nearly to that of the purple heather among which it lies, as do the richly-speckled eggs. The partridge has a double protection. It is difficult to pick out her quiet brown plumage from a hedge-bottom so long as she remains still. She adopts the duns and browns and yellows of the dead leaves, among which she crouches. When she leaves her eggs she is careful to cover them with dead oak-leaves; but this seems almost superfluous, for there is no great contrast between the tint of the eggs and that of the leaves among which they lie. A hen pheasant lying in a bracken-bed is equally difficult to detect; and this applies particularly to all the young of the game birds just mentioned. The bright, dark eyes of birds and animals frequently betray them, as these are almost invariably large and prominent. A short-eared owl on a peat-moss I have mistaken for a clod of turf, and a gaunt heron with wind-fluttered feathers for drift stuff caught in the swaying branches of the stream. Another characteristic case of protective imitation is furnished by the nightjar or goatsucker. This night-flying bird, half owl, half swallow, rests during the day on bare bits of limestone on the fells. Its mottled plumage exactly corresponds with the grey of the stones, and its eggs, in colour like its plumage, are laid upon the bare ground without the slightest vestige of a nest--and again entirely resemble the stone.