Caa-. XVI. Birds — Voting like Adult Females. 473 



which we see in our domesticated birds is, of course, the result 

 of some definite cause; and under natural and more uniform 

 conditions, some one tint, assuming that it was in no way 

 injurious, would almost certainly sooner or later prevail. The 

 free intercrossing of the many individuals belonging to the same 

 species would ultimately tend to make any change of colour, 

 thus induced, uniform in character. 



No one doubts that both sexes of many birds have had their 

 colours adapted for the sake of protection ; and it is possible 

 that the females alone of some species may have been modified 

 for this end. Although it would be a difficult, perhaps an 

 impossible process, as shewn in the last chapter, to convert one 

 form of transmission into another through selection, there would 

 not be the least difficulty in adapting the colours of the female, 

 independently of those of the male, to surrounding objects, 

 through the accumulation of variations which were from the 

 first limited in their transmission to the female sex. If the 

 variations were not thus limited, the bright tints of the male 

 would be deteriorated or destroyed. Whether the females alone 

 of many species have been thus specially modified, is at present 

 very doubtful. I wish I could follow Mr. Wallace to the full 

 extent; for the admission would remove some difficulties. Any 

 variations which were of no service to the female as a protection 

 would be at once obliterated, instead of being lost simply by not 

 being selected, or from free intercrossing, or from being elimin- 

 ated when transferred to the male and in any way injurious to 

 him. Thus the plumage of the female would be kept constant 

 in character. It would also be a relief if we could admit that 

 the obscure tints of both sexes of many birds had been acquired 

 and preserved for the sake of protection, — for example, of the 

 hedge-warbler or kitty-wren (Accentor modularis and Troglodytes 

 vulgaris), with respect to which we have no sufficient evidence 

 of the action of sexual selection. We ought, however, to be 

 cautious in concluding that colours which appear to us dull, are 

 not attractive to the females of certain species ; we should bear 

 in mind such cases as that of the common house-sparrow, 

 in which the male differs much from the female, but does not 

 exhibit any bright tints. No one probably will dispute that many 

 gallinaceous birds which live on the open ground, have acquired 

 their present colours, at least in part, for the sake of protection. 

 We know how well they are thus concealed; we know that 

 ptarmigans, whilst changing from their winter to their summer 

 plumage, both of which are protective, suffer greatly from birds 

 of prey. But can we believe that the very slight differences in 

 tints and markings between, for instance, the female black-grouse 



