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Show 230 SEXUAL SELECTION: BIRDS. l'AJ\1' II. As sexual selection depends on so fluctuating au element as taste, we can understand how it is that within the same group of birds, with habits of life noa~·ly the same there should exist white or nearly wl11te, as well a~ black, or nearly black species,-for instance, white and black cockatoos, storks, ibises, swans, terns, and petrels. Piebald. birds likewise sometimes occur in the same groups, for instance, the black-necked .swan, certain terns, and the common magpie. That a strono- contrast in colour is agreeable to birds, we may co~clude, by looking through any large collection of specimens or series of coloured plates, for the sexes frequently differ from each other in the male having the pale parts of a purer white, and the variously coloured dark parts of still darker tints than in the female. It would even appear that mere novelty, or change for the sake of change, has sometimes acted like a charm on female birds, in the same manner as changes of fashion with us. The Duke of Argyll says,5G-and I am glad to have the unusual satisfaction of following for even a short distance in his footsteps-" I am more "and more convincecl that variety, mere variety, must "be admitted to be an object and an aim in Nature.'' I wish the Duke had explained what he here means by Nature. Is it meant that the Creator of tho universe ordained diversified results for His own satisfaction, or for that of man? The former notion seems to me as much wanting in due reverence as the latter in probability. Capriciousness of taste in the birds themselves appears a more fitting explanation. For example ; the males many olhcr species arc black. This fact supports the conjecture that these conspicuous colours may aid the sexes in finding each other dming the breeding-season. so 'Tho Journal of Travel,' edited by A. Murray, vol. i. 1868, p. 286. OIIAP. XVI. NOVELTY ADMIRED. 231 of some parrots can hardly be said to be more beautiful at least according to our taste, than the females, but the~ differ from them in such points, as the male havmg a rose-coloured collar instead of, as in the ~omale, "a bright emeralcline narrow green collar;" or m t~e male. ha~ing ,~ b.lack collar instead of" a yellow dom1-collar m front, w1th a pale roseate instead of a pln~-bl~e head.57 As so many male birds have for th01r chief ornament elongated tail-feathers or elongated crests, the shortened tail, formerly described in the male of a humming-bird, and the shortened crest of the ~ale goosander almost seem like one of the many opposite changes of fashion which we admire in our own dresses. ~orne members of the heron family offer a still more curwus case of novelty in colouring having -apparently been appreciated for the sake of novelty. 'l'he young of the Ardea aE~ha are white, the adults being dark slate-coloured; and not only the young, but the adults of the allied Buphus coromandus in their winter plumage are white, this colour changino- into a rich golden-buff during the breeding-season. It is incredible that the young of these two species, as well as of some othe~· members of the same family/8 should have been specially rendered pure white and thus made conspicuous to their enemies; or that the adults of one of tbe.se two .species should have been specially rendered wlnte durmg the winter in a country which is never 57 See Jordon en the genus Palooomis 'Bn·ds of India' vol 1· IJ 258-2GO. ' , ' . . . . "8 '~'he yo~ng of .Lh·dea ntjescena and .A. camtlea of tho U. States are lJ.l~ew1se wl11te, the adults being colom<;cl in accordance with their specLlic, names. Auuubou (' Omith. Biogmphy,' vol. iii. p. 416; vol. iv. J). 58) seems ~ather pleased. at the thought that this remarkable change ~Jf plumuge 'Hll greatly "dtseouccrt the systcmaii~:>ts." |