BIRDS— YOUNG LIKE ADULT FEMALES. 4G5 



certain sub-breeds of the game-fowl. In which the females are very 

 different, whilst the males can hardly be distinguished." 



As I account so largely by sexual selection for the differences 

 between the males of allied species, how can the differences be- 

 tween the females be accounted for in all ordinary cases? We 

 need not here consider the species which belong to distinct genera; 

 for with these, adaptation to different habits of life, and other 

 agencies, will have come into play. In regard to the differences 

 between the females within the same genus, it appears to me 

 almost certain, after looking through various large groups, that 

 the chief agent has been the greater or less transference to the 

 female of the characters acquired by the males through sexual se- 

 lection. In the several British finches, the two sexes differ either 

 very slightly or considerably; and if we compare the females of 

 the greenfinch, chaffinch, goldfinch, buUfincn, crossbill, sparrow, 

 &c., we shall see that they differ from one another chiefly in the 

 points in which they partially resemble their respective males; 

 and the colors of the males may safely be attributed to sexual se- 

 lection. With many gallinaceous species the sexes differ to an ex- 

 treme degree, as with the peacock, pheasant, and fowl, whilst with 

 other species there has been a partial or even complete transfer- 

 ence 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 colors being 

 much duller. In the guinea-fowl the two sexes are indistinguish- 

 able. 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 Trago- 

 pan pheasants. 



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

 of characters from the male to the female has been effected ap- 

 parently at a remote period, the male having subsequently under- 

 gone .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 colored 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 



» 'Variation of Animals, &o., under Domestication,' vol. i. p. 251. 

 31 



