CaAF, XVI. Birds— -Conspicuous Colours. 491 



be forgotten, in which it was shewn 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 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 



likewise 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 



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 



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 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 coloured, such as the numerous black, white, or 



piebald species ; and these colours are probably the result of 



sexual selection. With the common blackbird, capercailzie, 



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



the birds of paradise (Lophorina «£r«), the males alone are black, 



whilst 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 transmission 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 coloured, 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 coloured beak; of the scoter-drake 



(Oidemia), in the red beak of the chough {Corvm (/raculus, 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 colour, with which these 



organs are ornamented. 51 The naked skin, also, at the base of the 



51 No satisfactory explanation has size, and still less of the bright 

 ever been offered of the immense colours, c{ the toucan's beak. Mr 



