438 THE DESCENT OF MAN. 



CHAPTER XV. 



BIRDS— Continued. 



Discussion as to why the males alone of some species, and both sexes 

 of others, are brightly colored— On sexually-limited inheritance, as 

 applied to various structures and to brightly-colored plumage— 

 Nidiflcation in relation to color— Loss of nuptial plumage during 

 the winter. 



We have in this chapter to consider, why the females of many 

 birds have not acquired the same ornaments as the male; and 

 why, on he other hand, both sexes of many other birds are 

 equally, or almost equally, ornamented? In the following chap- 

 ter we shall consider the few cases in which the female is more 

 conspicuously colored than the male. 



In my 'Origin of Species'' I briefly suggested that the long tail 

 of the peacock would be inconvenient, and the conspicuous black 

 color of the male capercailzie dangerous, to the female during 

 the period of incubation; and consequently that the transmission 

 of these characters from the male to the female offspring had 

 been checked through natural selection. I still think that this 

 may have occurred in some few instances: but after mature re- 

 flection on all the facts which I have been able to collect, I am 

 now inclined to believe that when the sexes diSer, the successive 

 variations have generally been from the first limited in their 

 transmission to the same sex in which they first arose. Since 

 my remarks appeared, the subject of sexual coloration has been 

 discussed in some very interesting papers by Mr. Wallace,^ v/ho 

 believes that in almost all cases the successive variations tended 

 at first to be transmitted equally to both sexes; but that the 

 female was saved, through natural selection, from acquiring the 

 conspicuous colors of the male, owing to the danger which she 

 would thus have incurred during incubation. 



This view necessitates a tedious discussion on a diflScult point, 



1 Fourth edition, 1866, p. 241. 



" 'Westminster Review,' July, 1867. 'Journal of Travel,' vol. i. 1868, 

 p. 73. 



