Pheasants' eggs vary strangely in shade: they show a much wider range of shading than partridges', from almost white through the most delicate gradations of blue-green and olive-brown to the rich, warm hue of the nightingale's egg. The keeper prefers the eggs with the deeper tones, persuading himself that they will produce the strongest chicks. He has small faith in the fertility of eggs that are very light in hue, and he holds to an idea that if a light, sky-blue egg hatches at all it will produce a pied chick. When a hen lays in another's nest, it is rather by some subtle distinction of shape than by colour that the keeper discovers the trespasser's eggs: for the eggs of one bird may vary much in shade. The nest is a simple affair, merely a shallow hollow, scratched out, ringed by dry grass or leaves or any dead material of the sort within easy reach; if dry grass is plentiful a generous supply fringes the hollow, but a pheasant is not one to trouble to fetch and carry for her nest. Cunning as she may be in the choice of a site, no instinct or reason prompts her to go a yard away to collect material, however plentiful at that short distance, for comfort and warmth. Her fabric, plentiful or scanty, is arranged in a typical fashion. Standing in the middle of her scraped-out hollow, she throws the bits of grass or the leaves over her back, so that the margin of the nest corresponds to the size of her body. Sometimes a fowl is seen going through this performance; the goose also employs this primitive instinctive manner of gauging her nest's dimensions.