This same principle applies to many birds belonging to various groups, in which the young closely resemble each other, and differ much from their respective adult parents. The young of almost all the Gallinaceæ, and of some distantly-allied birds such as ostriches, are whilst covered with down longitudinally striped; but this character points back to a state of things so remote that it hardly concerns us. Young crossbills (Loxia) have at first straight beaks like those of other finches, and in their immature striated plumage they resemble the mature redpole and female siskin, as well as the young of the goldfinch, greenfinch, and some other allied species. The young of many kinds of buntings (Emberiza) resemble each other, and likewise the adult state of the common bunting, _E. miliaria_. In almost the whole large group of thrushes the young have their breasts spotted—a character which is retained by many species throughout life, but is quite lost by others, as by the _Turdus migratorius_. So again with many thrushes, the feathers on the back are mottled before they are moulted for the first time, and this character is retained for life by certain eastern species. The young of many species of shrikes (Lanius), of some woodpeckers, and of an Indian pigeon (_Chalcophaps Indicus_), are transversely striped on the under surface; and certain allied species or genera when adult are similarly marked. In some closely-allied and resplendent Indian cuckoos (Chrysococcyx), the species when mature differ considerably from each other in colour, but the young cannot be distinguished. The young of an Indian goose (_Sarkidiornis melanonotus_) closely resemble in plumage an allied genus, Dendrocygna, when mature.[229] Similar facts will hereafter be given in regard to certain herons. Young black grouse (_Tetrao tetrix_) resemble the young as well as the old of certain other species, for instance the red grouse or _T. scoticus_. Finally, as Mr. Blyth, who has attended closely to this subject, has well remarked, the natural affinities of many species are best exhibited in their immature plumage; and as the true affinities of all organic beings depend on their descent from a common progenitor, this remark strongly confirms the belief that the immature plumage approximately shews us the former or ancestral condition of the species.