1S6 SEXUAL SELECTION: BIRDS. [Part II. 



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 undistinguishable. 

 There is no improbability in the plain, though peculiar 

 spotted plumage of this latter bird having been acquired 

 through sexual selection by the males, and then trans- 

 mitted to both sexes ; for it is not essentially different 

 from the much more beautifully-spotted plumage, charac- 

 teristic of the males alone of the Tragopan pheasants. 



It should be observed that, in some instances, the trans- 

 ference of characters from the male to the female has been 

 effected apparently at a remote period, the male having 

 subsequently undergone great changes, without transfer- 

 ring 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 conse- 

 quently 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 plainly 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, at least to a certain extent, influ- 

 enced by sexual selection. 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 shows 

 in her tail a trace of the curved fork. 



" Macgillivray, 'Hist. British Birds,' vol. i. pp. 1Y2-174. 



