=Protective Colouring of Birds.=--The protective colour of the plumage of certain birds is the great source of their safety during incubation. For instance, birds which nidificate on the ground, such as Black and Red Grouse, Pheasants, Partridges, and Sandpipers, all subject to the depredations of winged and creeping enemies, are preserved by the modification of their tints. The same means of security attend their eggs and downy young, even the extreme simplicity of their nests aiding the escape of detection. Birds whose down has protected them during the early part of their history, become aware of the dangers which threaten a more conspicuous plumage, which is a marvellous thing, whether acquired by reasoning or instinct. This is proved by the action of birds of the same order. The Golden Plover, with plumage in harmony with the surroundings of her nest (her feathers being still further subdued in colour during the breeding season), sits much closer than the Green Plover, although a shyer bird, with eggs possessing the same protective qualities. The Green Plover knows her plumage is much more conspicuous than her eggs, and quietly slips away before danger approaches half so near as the golden plover will allow it. I am surprised to find so great an authority as Darwin assert that "the species which represent each other in distinct countries will almost always have been exposed to different conditions, but we can hardly attribute to this action the modification of the plumage in the males alone, seeing that the females and the young, though similarly exposed, have not been affected." Possibly such may be the case where no protective modification is necessary in the female or young; but what about the fact that female Red Grouse differ much in the colour of their plumage, according to the conditions under which they live, though the males are left totally unaffected? Instance the female Grouse, known as the "Moss-hen," always found on the highest and most exposed situations where there is little cover, consequently great need of harmonising colours: a strong point, I venture to assert, in favour of protective utility. Moulting has been rendered subject to the law of preservation in a remarkable degree, for where birds are open to periodical changes of surrounding conditions which materially affect their existence, they are provided with an extra moult. For example, the Ptarmigan's plumage is pure white for winter snow, and brown for summer heather.