| OCR Text |
Show 166 SEXUAL SELECTION: BIRDS. PAtU' li. vVe are lell to a nearly similar conclusion with respect to the length of the tail in the various species· of pheasants. In the Eared pheasant ( Crossoptilon auritum) the tail is of equal length in both sexes, namely, sixteen or seventeen inches; in the common pheasant it is about twenty inches long in the male, and twelve in the female; in Soommerring's pheasant, thirty-seven inches in the male, and only eight in the female ; and lastly in Reeve's pheasant it is sometimes actually seventy-two inches long in the male and sixteen in the female. Thus in the several species, the tail of the female differs much in length, irrespectively of that of the male; and this can be accounted for as it seems to me, with much more probability, by the laws of inheritance,-that is by the successive variations having been from the first more or less closely limited in their transmission to the male sex,-than by the agency of natural selection, owing to the length of tail having been injurious in a greater or less degree to the females of the several species. We may now consider Mr. Wallace's arguments in regard to the sexual coloration of birds. He believes that the bright tints originally acquired through sexual selection by the males, would in all or almost all cases have been transmitted to the females, unless the transference bad been checked through natural selection. I may here remind the reader that various facts bearing on this view have already been given under reptiles, amphibians, fishes, and lepidoptera. Mr. Wallace rests his belief chiefly, but not exclusively, as we shall see in the next chapter, on the following statement, 8 that when both sexes are coloured in a strikingly- & 'Journal of Travel,' edited Ly A. Murray, vol. i. 18G8, p. 78. CllAP. XV. COLOUR AND NIDIFICATION'. Hi7 conspicuous manner the nest is of such a nature as to conceal the sitting bird; but when there is a marked contrast of colour between the sexes the male beino- ' 0 gay and the female dull-coloured, the nest is open and exposes the sitting bird to view. This coincidence, as far as it goes, certainly supports the belief that the fem~les which sit on open nests have been specially modified for the sake of protection. Mr. Wallace admits that there are, as might have been expected, some exceptions to his two rules, but it is a question whether the exceptions are not so numerous as seriously to invalidate them. There is in the first place much truth in the Duke of Argyll's remark 9 that a large domed nest is more consricuous to ~n enemy, especially to all tree-haunting carmvorous ammals, than a smaller open nest. Nor must we forget tl_1at with many birds which build open nests the males s1t on the eggs and aid in feeding the young as well as the females : this is the case for ins~ ance~ with Pyr~nga m~tiva/0 one of the most ~plendid birds m the Umted States, the male being vermilion, and the female light brownish-green. Now if brilliant c?l~urs bad been extremely dangerous to birds whilst s1ttmg on their open nests, the males in these cases would have suffered greatly. It might, however, be of such paramount importance to the male to be brilliantly coloured, in order to beat his rivals, that this would more than compensate for some additional danger. Mr. Wal~ace admits ~h~t with the King-crows (Dicrurus), Orwles, and P1tt1dro, the females are conspicuously coloured, yet they build open nests ; but he urges that the birds of the first group are highly pug- : 0 ' Journal of Tru~ol,' edited by A. Murray, vol. i, 1868, p. 281. Auuubon, 'Ormthological Biography,' vol. i. p. 233. |
