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Show SEXUAL SELECTION. PAr..l' ]J. CHAPTER XIII. SECONDARY SEXUAL CHARACTERS oF Bmus., Sexual differences- Law of btL1e- Special weapons- Vocal orrraus- Instrumental music - Love- antics and danc~sD~ corations, permanent and seasonal- Double and smglc annual moults- Display of ornaments by the males. SECONDARY sexnnl characters are more diversified and conspicuous in birds, though not perh~ps entailing more important chanrres of structure, than m any other class of animals. I :hall, therefore, treat the subject at considerable length. Male birds som~times,. though rarely, possess special weapons for fightm~ w1th each othe~·· 1,hey charm the females by vocal or mstrumental musw of the most varied 1-:inds. rrhey are ornamented by ull sorts of combs, wattles, protuberances, horns, airdistended sacs, topknots, naked shafts, plumes and lengthened feathers gracefully springing from all parts of the body. The beak and naked skin about the head, and the feathers are often gorgeously coloured. The males sometimes pay their court by dancing, or by fantastic antics performed either on the ground or in the air. In one instance, at least, the male emits a musky odour which we may suppose serves to charm or excite the female; for that excellent observer, 1\fr. Ramsay/ says of the Australian musk-duck (Biziura lobata) that" the " smell which the mule emits during the summer " months is confined to that sex, and in some indi" viduals is retained throughout the year; I have never 1 • luis,' vol. iii. (new series) 1867, p. 414. CHAP. XIll. BIRDS. 39 "' even in the breeding-season, shot a female wl1ich had ·" any smell of musk." So powerful is this odour during the pairing-season, that it can be detected long before .the bird can be seen.2 On the whole, Lirds appear to be the most msthetic of all animals, excepting of course man, and they have nearly the same taste for tlle beautiful as we have. This is shewn by our enjoyment of the singing of birds, and Ly our women, both civilised and savage, decking their heads with borrowed plumes, and using gems which are hardly more brilliantly ,.coloured than the naked skin and wattles of certain birds. Before treating of the characters with which we are here more particularly concerned, I may just allude to certain differences between the sexes which apparently depend on differences in their habits of life ; for such -cases, though common in the lower, are rare in the higher classes. 1,wo humming-birds belonging to the genus Eustephanus, which inhabit the island of Juan Fernandez, were long thought to be specifically distinct, but are now known, as 1\fr. Gould informs me, to be the sexes of the same species, and they differ slio-htlv in the form of the beak. In another genus of bu~mii;g-birds ~Grypus), the beak of the male is senated alone>' the . b mm·gm and hooked at the extremity, thus differing much from that of the female. In the curious N eomorpha of New Zealand, there is a still wider difference in the form of the beak; and lVIr. Gould has been informed .that the male with his ''straight and stout beak" tears ·off the bark of trees, in order that the female may feed on the uncovered larvre with her weaker and more ·curved bea.k. Something of the same Jrind may be ·Observed with our goldfinch ( Oarduelis elegans), for I 2 Gould, ' Handbook to the Birds of Austml;~,· 1805, vol. ii. p. 383. |