Mr. Darwin has devoted four chapters of his _Descent of Man_ to the colours of birds, their decorative plumage, and its display at the pairing season; and it is on this latter circumstance that he founds his theory, that both the plumage and the colours have been developed by the preference of the females, the more ornamented males becoming the parents of each successive generation. Any one who reads these most interesting chapters will admit, that the fact of the display is demonstrated; and it may also be admitted, as highly probable, that the female is pleased or excited by the display. But it by no means follows that slight differences in the shape, pattern, or colours of the ornamental plumes are what lead a female to give the preference to one male over another; still less that all the females of a species, or the great majority of them, over a wide area of country, and for many successive generations, prefer exactly the same modification of the colour or ornament. The evidence on this matter is very scanty, and in most cases not at all to the point. Some peahens preferred an old pied peacock; albino birds in a state of nature have never been seen paired with other birds; a Canada goose paired with a Bernicle gander; a male widgeon preferred a pintail duck to its own species; a hen canary preferred a male greenfinch to either linnet, goldfinch, siskin, or chaffinch. These cases are evidently exceptional, and are not such as generally occur in nature; and they only prove that the female does exert some choice between very different males, and some observations on birds in a state of nature prove the same thing; but there is no evidence that slight variations in the colour or plumes, in the way of increased intensity or complexity, are what determines the choice. On the other hand, Mr. Darwin gives much evidence that it is _not_ so determined. He tells us that Messrs. Hewitt, Tegetmeier, and Brent, three of the highest authorities and best observers, "do not believe that the females prefer certain males on account of the beauty of their plumage." Mr. Hewitt was convinced "that the female almost invariably prefers the most vigorous, defiant, and mettlesome male;" and Mr. Tegetmeier, "that a gamecock, though disfigured by being dubbed, and with his hackles trimmed, would be accepted as readily as a male retaining all his natural ornaments."[126] Evidence is adduced that a female pigeon will sometimes turn antipathy to a particular male without any assignable cause; or, in other cases, will take a strong fancy to some one bird, and will desert her own mate for him; but it is not stated that superiority or inferiority of plumage has anything to do with these fancies. Two instances are indeed given, of male birds being rejected, which had lost their ornamental plumage; but in both cases (a widow-finch and a silver pheasant) the long tail-plumes are the indication of sexual maturity.