216 SEXUAL SELECTION: BIRDS [Part II. 



billed birds are songsters ; and a discussion in a former 

 chapter should not be forgotten, in which it was shown 

 that the best songsters are rarely ornamented with bright 

 tints. It would appear that female, birds, as a general 

 rule, have selected their mates either for their sweet voices 

 or gay colors, but not for both charms combined. Some 

 species which are manifestly colored for the sake of pro- 

 tection, such as the jack-snipe, woodcock, and night-jar, 

 are likewise marked and shaded, according to our stand- 

 ard of taste, with extreme elegance. In such cases we 

 may conclude that both natural and sexual selection have 

 acted conjointly for protection and ornament. Whether 

 any bird exists which does not possess some special at- 

 traction, 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. 



There are many birds both ,sexes of which are conspic- 

 uously though not brilliantly colored, such as the numer- 

 ous black, white, or piebald species ; and these colors are 

 probably the result of sexual selection. With the common 

 blackbird, capercailzie, black-cock, blaGk Scoter-duck (Oi- 

 demia), 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 that blackness in these cases has been a sexually- 

 selected character. Therefore it is in some degree proba- 

 ble 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 transmission to 



