Page:The Zoologist, 4th series, vol 6 (1902).djvu/400

340 distinct from the same stages of A. albifrons; and, as I have before said, I can find no proper description of these stages, it will be necessary in proving my case to publish a full but brief description of these and the other leading features in my two series of birds. I ought perhaps to say that the stock of books available to me here is limited—I particularly lack American works—and I should like it to be understood that I do not positively assert that no proper description of these stages of plumage has ever been published, but that I cannot find any.

The immature plumage of any of the Wild Geese may always be known by the small size of the feathers clothing the body; in first plumage the feathers are not half the size of those of an adult bird. The feathers gradually increase in size as the bird advances towards January and February. With the growth of these feathers there is a change in the colouring matter, independently of a moult. But when the black feathers begin to appear on the breast, they are frequently, but not always, newly moulted feathers. I have plenty of evidence showing the black colouring matter being transmitted into drab feathers; indeed, this deposition of the black pigment goes on slowly until the whole under parts become jet-black. In the case of the immature birds, of A. gambeli especially, advancing towards maturity, it is first a gradual extraction of the dark colouring matter from the feathers, eventually leaving the breast and under parts almost if not quite white; then the full drab colour of the adult bird gradually deepens, and with it the black colour begins to appear. As I have before said, these changes are accompanied by a moult, and probably by the time the breeding period comes round the whole body has been clothed in new feathers.

I have given these general facts here, as it will be necessary to keep them in view in connection with the following descriptions.

The general appearance of this bird's first plumage is a very dark blackish brown; but compare this first plumage with the black-breasted breeding stage, and it is easy to see that this young bird belongs to a parent who finds black under parts useful to it as a protective colouring during the breeding season.