BIRDS. 559 



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 con- 

 clude that both natural and sexual selection have acted 

 conjointly for protection 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 protection, 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, 

 blackcock, black scoter-duck (Oidemia), and even with one 

 of tlie birds of paradise {LopJiorina air a) the males alone 

 are black, while the females are brown or mottled; 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 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 blackcock and caper- 

 cailzie, in the brightly and variously colored beak of the 

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

 (Corvus graculiis, Linn.), of the black swan and the black 

 stork. This leads me to remark that it is not incredible 

 that toucans may owe the enormous size of their beaks to 

 sexual selection, for the sake of displaying the diversified 

 and vivid stripes of color with wliich these organs are 

 ornamented.* The naked skin, also, at the base of the 



* No satisfactory explanation has ever been offered of the immense 



