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Show BO SEXUAL SELECTION: BIRDS. PArt'l' ll. more deeply embedded in the adult male thn,n in the female or young mn,le. In the male ~fcrgans?r the enlarged portion of the trachea is furmsh~cl with an additional pn,ir of muscles.4r. But the meanm.g of .these differences between the sexes of many Anat1dro IS not at all understood· for the male is not always the more vociferous ; thns ,~ith the common duel~:, the male hisses, whilst the female utters a loud quack.46 In Loth exes of one of tho cranes ( Grus virgo) . the trachea ~Jmte~ratc~ the stemum, but presents '' cm·tam sexual !nochficatwns. In the male of the bln,ck stork there If:l also a wellmarked sexual difference in the length n,ud curv11ture of the bronchi.47 So that highly important structures have in these cases been modified according to sex. It is often difficult to conjecture whether the many strange cries and noteE~, uttered by male birds during the breeding-season, servo as a charm or merely as a call to the female. 'l'ho soft cooing of tho turtle-dove and of many pigeons, it may be presumerl, pleases the female. ·when the female of the wild turkey utters her call in the morning, the male answers by a different note from the gobbling noise which he makeR, when with erected feathers, rustling wings and distended wattles, he puffs and struts before her.48 The spel of the black-cock certainly serves as a call to the female, for it has been known to Lring four or :five females 4:; Bil:lhop, in 'fot1d's 'Cyclop. of Anat. and Phys.' vol. iv. p. H!l!J. •IG Tho spoonbill (Platalea) hos its trachea convoluted iuto a figure Qf oight, ond yet this bird (Jordon,' Birds of India,' vol. iii. p. 760) is mute; but Mr. Blyth informs me that the convolutions arc not constantly present, so that perhaps they nrc now tending towards abortion. 47 'Elements of Comp. Anat.' by R. Wagner, Eng. translat. 1845, p. 111. With respect to the swan, as given above, Ynrrcll'::~ 'llii:!t. of llritish llirds,' 2nd edit. 18'15, vol. iii. p. 193. ~s C. L. Bonaporte, quoted in the 'Naturalist Library: Birds,' vol. xiv. p. 12G. CHAP. Xlli. INSTRUMENTAL MUSIC. 61 from a distance to a male under confinement· but the bh:ck-cock continues his spel for hours' dm·ina; success1 ve days, and in the case of the . ·1 · "with an ao-on f . " capercai Zie b Y o passwn, we are led to suppose that the females which are already present are th, cha n. necl. 49 . ,.,,1 . us J.. le VOice of the common rook is known to alter durmg the breedinab -season , and I·s tl1 ere1i'o re I• n some way sexual6· o Bu· t wh,". t sllall we say a Lo ut tIl e harsh screams of, for instance ' some 1\-.I · nd s of macaws · have these birds as bud taste for musical sounds a~ 1th ey ap·p arently have for colour' .J 'udgt'noa bY the m. - Iarmomous co~tr~st of their bright yell~w and blue plumage? It IS. mdeed possible that the loud voices of many rna~e bll'ds may be the result, without an aclvnnta~·e bemg thus gained, of the inherited effects [r the. contmued use of their vocal organs, when they are excited by the strong passions of love jealousy and rage; but to this point we shall recur when we tr~at of quadrupeds. I We have . as ye~ spoken only of the voice, but the m~les of variOus bn·ds practise, during their courtship w at ~ay be called instrumental music. Peacock; and Bud~ of Paradise rattle their quills together, and the Vlbra~ory movement apparently senes merel t~ mal~e a nOise, for it can hardly add to the b / of their plum. 1' 1 eau y a . age. ur \:ey-cocks scrape their wino-s aoa~nst the ground, and some kinds of o-rouse th~s pro uco a buzzing sound. Another North American g:ou~e, the. Tetrao urnbellus, when with his tail erect, ~Is ruffs displa~ed, ."he shows off his :finery to the fe.males, who he hid in the neio-hbourhood " d. rapidly ' 'th h' "l b ' rums YI IS owered wings on the trunk of a ~0 L. Lloytl 'Tl e G n· ·d - 50 J . ; . 1 arne n s of Swotlon,' &c., 18G7, p. 22 81 onnOI, Plnlosoph. 'Transactions,' 182·1, p. 20. ' . .. |