634 THE DESCENT OF MAN 



manifestly colored for the sake of protection, such as the 

 jack-snipe, woodcock, and night-jar, are likewise marked 

 and' shaded, according to our standard of taste, with ex- 

 treme elegance. In such cases we may conclude that both 

 natural and sexual selection have acted conjointly for pro- 

 tection and ornament. Whether any bird exists which does 

 not possess some special attraction, by which to charm the 

 opposite" sex, may be doubted. When both sexes are so 

 obscurely colored that it would be rash to assume the 

 agency of sexual selection, and when no direct evidence 

 can be advanced showing that such colors 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 conditions of life. 



Both sexes of many birds are conspicuously though not 

 brilliantly colored, such as the numerous black, white, or 

 piebald species, and these colors are probably the result of 

 sexual selection. 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, while the females are brown or mottled; and 

 there can hardly be a doubt th^t blackness in these cases 

 has been a sexually selected character. Therefore it is in 

 some degree probable that the complete 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 selection, accompanied by equal transmis- 

 sion to both sexes; for blackness can hardly serve in any 

 case as a protection. With several birds in which the male 

 alone is black, and in others in which both sexes are black, 

 the beak or skin about the head is brightly colored, and the 

 contrast thus afforded adds much to their beauty; we see 

 this in the bright yellow beak of. the male blackbird, in 

 the crimson skin over the eyes of the black-cock and 

 capercailzie, in the brightly and variously colored beak of 

 the scoter-drake (Oidemia), in the red beak of the chough 

 iCorvus graculus, Linn.), of the black swan, and the black 



