Chap. XVI. Birds — Young like A dult Females. 47 1 



another chiefly in the points in which they partially resemble 

 their respective males ; and the colours of the males may safely 

 be attributed to sexual selection. With many gallinaceous 

 species the sexes differ to an extreme degree, as with the peacock, 

 pheasant, and fowl, whilst with other species there has been a 

 partial or even complete transference of character from the male 

 to the female. The females of the several species of Polyplectron 

 exhibit in a dim condition, and chiefly on the tail, the splendid 

 ocelli of their males. The female partridge differs from the 

 male only in the red mark on her breast being smaller ; and the 

 female wild turkey only in her colours being much duller. In 

 the guinea-fowl the two sexes are indistinguishable. There is no 

 improbability in the plain, though peculiarly spotted plumage 

 of this latter bird having been acquired through sexual selection 

 by the males, and then transmitted to both sexes ; for it is not 

 essentially different from the much more beautifully spotted 

 plumage, characteristic of the males alone of the Tragopan 

 pheasants. 



It should be observed that, in some instances, the transference 

 of characters from the male to the female has been effected 

 apparently at a remote period, the male having subsequently 

 undergone great changes, without transferring to the female any 

 of his later-gained characters. For instance, the female and the 

 young of the black-grouse (Tetrao tetrix) resemble pretty closely 

 both sexes and the young of the red-grouse (T. scoticus) ; and we 

 may consequently infer that the black-grouse is descended from 

 some ancient species, of which both sexes were coloured in 

 nearly the same manner as the red-grouse. As both sexes of 

 this latter species are more distinctly barred during the breeding 

 season than at any other time, and as the male differs slightly 

 from the female in his more strongly-pronounced red and brown 

 tints, 10 we may conclude that his plumage has been influenced 

 by sexual selection, at least to a certain extent. If so, we may 

 further infer that the nearly similar plumage of the female black- 

 grouse was similarly" produced at some former period. But 

 since this period the male black-grouse has acquired his fine 

 black plumage, with his forked and outwardly- curled tail- 

 feathers; but of these characters there "has hardly been any 

 transference to the female, excepting that she shews in her tail 

 a trace of the curved fork. 



We may therefore conclude that the females of distinct though 



allied species have often had their plumage rendered more or 



less different by the transference in various degrees, of characters 



acquired by the males through sexual selection, both during 



10 Macgillivray, ' Hist. British Birds,' vol. i. pp. 172-174. 



