Chap. XIII.] VOCAL MUSIC. 57 



long-sustained fluty note. The head-crest and neck-ap- 

 pendage are rudimentary in the female. 44 



The vocal organs of various web-footed and wading 

 birds are extraordinarily complex, and differ to a certain 

 extent in the two sexes. In some cases the trachea is 

 convoluted, like a French horn, and is deeply embedded 

 in the sternum. In the wild-swan (Cygnus ferus) -it is 

 more deeply embedded in the adult male than iii, the 

 female or young male. In the male Merganser the en- 

 larged portion of the trachea is furnished with an addi- 

 tional pair of muscles. 45 But the meaning of these differ- 

 ences between the sexes of many Anatidse is not at all 

 understood; for the male is not always the more vo- 

 ciferous ; thus with the common duck, the male hisses, 

 while the female utters a loud quack. 46 In both sexes of 

 one of the cranes ( Grus virgo) the trachea penetrates the 

 sternum, but presents " certain sexual modifications." In 

 the male of the black stork there is also a well-marked 

 sexual difference in the length and curvature 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 notes, uttered by male birds during the 

 breeding-season, serve as a charm or merely as a call to 



44 Bates, ' The Naturalist on the Amazons,' 1863, vol. ii. p. 284 ; Wal- 

 lace, in ' Proc. Zool. Soc.' 1850, p. 206. A new species, with a still 

 larger neck-appendage (C. pcndidiger), has lately been discovered, sec 

 * Ibis,' vol. i. p. 457. 



45 Bishop, in Todd's ' Cyclop, of Ana't. and Phys.' vol. iv. p. 1499. 



46 The spoonbill (Platalea) has its trachea convoluted into a figure of 

 eight ; and yet this bird (Jerdon, 'Birds of India,' vol. iii. p. 763) is 

 mute ; but Mr Blyth informs me that the convolutions are not constant- 

 ly present, so that perhaps they are now tending toward abortion. 



47 'Elements of Comp. Anat.' by R. Wagner, Eng. translat. 1845, p, 

 111. With respect to the swan, as given above, YarrelTs 'Hist, of Brit- 

 ish Birds,' 2d edit. 1845, vol. iii. p. 193. 



