226 SEXUAL SELECTION : BIRDS. Part XL 



mented with bright tints. It would appear that female 

 birds, as a general rule, have selected their mates 

 either for their sweet voices or gay colours, but not 

 for both charms combined. Some species which are 

 manifestly coloured for the sake of protection, such 

 as the jack-snipe, woodcock, and night-jar, are like- 

 wise marked and shaded, according to our standard 

 of taste, with extreme elegance. In such cases we 

 may conclude that both natural and sexual selection 

 have acted conjointly for ]3rotection and ornament. 

 Whether any bird exists which does not possess some 

 sj)ecial attraction, by which to charm the opposite sex, 

 may be doubted. When both sexes are so obscurely 

 coloured, that it would be rash to assume the agency 

 of sexual selection, and when no direct evidence can 

 be advanced shewing that such colours serve as a pro- 

 tection, it is best to own complete ignorance of the 

 cause, or, which comes to nearly the same thing, to 

 attribute the result to the direct action of the con- 

 ditions of life. 



There are many birds both sexes of which are con- 

 spicuously, though not brilliantly coloured, such as 

 the numerous black, white, or piebald species ; and 

 these colours, are probably the result of sexual selec- 

 tion. With the common blackbird, capercailzie, black- 

 cock, black Scoter-duck (Oidemia), and even with one 

 of the Birds of Paradise (Lophorina atra), the males 

 alone are black, whilst the females are brown or mot- 

 tled ; and there can hardly be a doubt that blackness 

 in these cases has been a sexually selected character. 

 Therefore it is in some degree probable that the com- 

 plete or partial blackness of both sexes in such birds 

 as crows, certain cockatoos, storks, and swans, and many 

 marine birds, is likewise the result of sexual selec- 

 tion, accompanied by equal transmission to both sexes ; 



