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Show 226 SEXUAL SELECTION: BIRDS. PAuT n. mcntecl with bright tints. It would appear th~t fcmn1e birds, as a general rule, have selecteJ their mates: either for their sweet voices or gay col?urs, ~nt not for both charms combined. Some speciCs '~lnch are manifestly coloured for tho sake o~ pr~tectJOn, s.uch as the jack-snipe, woodcock, and lllght-Jar, are hkewise marked and shaded, according to our standard of taste, with extreme elegance. In such enses ."'e may conclude that both natural a_nd sexual seleetw~ have acted conjointly for protectiOn anrl ornament. Whether any bird exists which does not posses~ 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 sexu~l selection, and when no direct evide~1ce can be advanced shewing that such colours serve as a protection it is best to own complete ignorance of the cause ~r which comes to nearly tho same thing, to attribnte' 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 specws ; and these colours, are probably the result of s~x~al selection. With the common blackbird, capercmlz1e, blackcock, 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 mottled; and .. ther~ can hardly be a doubt that blackness in these cases has been a sexually selected character. Therefore it is in some de()'ree probable that the complete or partial blackness ~f both sexes in such birds as crows, certain cockatoos, storks, and swans, and many marine birds, is likewise the result of sexual se1e~tion, accompanied by equal transmission to Loth sexes; CHAP. XVI. CONSPICUOUS COLOURS. 227 for .blacknes~ can hardly. serve in any case as a protectiOn. W1th several bu·ds, 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 greatly to their beauty; we see this in the bright yellow beak of the male blackbird, in the crimson skin over the eyes of th: black-cock and capercailzie, in the variously and ?nghtly-coloured beak of the Scoter-drake (Oidemia), 1~ the red beak of the chough (Corvus graculus, Linn.), of the black swan, and black stork. This leads me to remark that it is not .at all inc:edible 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 ornamentecl. 52 The naked skin at the base of the beak and round the eyes is likewise often brilliantly coloured · and Mr. Gould, in speaking of one species,S3 says that the colours of the beak "are doubtless in the finest " and ~ost brilliant state during the time of pairing." There IS no ?rea~er improbability in toucans being e_ncumbered w.Ith Immense beaks, though rendered as bght as possible by : their cancellated structure for an ob~ect falsely appearing to us unimportant, na~ely, the display of fine colours, than that the male Argus • 52 No sati.sfactory explanation has ever been offered of the immense s1z , nn~ still less of ihe bright colours, of the toucan's beak. 1\fr. Bates (· rhe Nat~ualist on the Amazons,' vol. ii. 1863, p. 341) states t~at they use th.eu b?ak for reaching fruit at the extreme tips of the bHtnehes; a~d hl~ew1se, as stated by other authors, for extracting eggs and young"buds from the nests of other birds. But as Mr. Bates admits, ~,ho beak can scarcely .be ?o~sidored a very perfectly-formed instru-ment forth~ end to wh1ch 1t 1s applied." 'l'l.to great bulk of the beak, ns sh?wn by 1t~ breadth, depth, as well as length, is not intelligible on th? 3 v10w, that 1t servos merely ns an organ of prehension. " Hamphaston corinatus, Gould's 'Monograph of Ramphnstidro.' Q 2 |