370 THE DESCENT OF MAN. 



understood; for the male is not always ttie more vociferous; 

 thus -with the common duck, the male hisses, whilst the female 

 utters a loud quack." 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.*" Highly important structures have, therefore, 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 the female. The soft 

 cooing of the turtle-dove and of many pigeons, it may be pre- 

 sumed, pleases the female. When the female of the wild turkey 

 utters her call in the morning, the male answers by a note which 

 differs from the gobbling noise made, when with erected feathers, 

 rustling wings and distended wattles, he puffs and struts before 

 her.* The spel of the black-cock certainly serves as a call to the 

 female, for it has been known to bring four or five females from 

 a distance to a male under confinement; but as the black-cock 

 continues his spel for hours during successive days, and in the 

 case of the capercailzie "with an agony of passion," we are led 

 to suppose that the females which are present are thus charmed.™ 

 The voice of the commo'n rook is known to alter during the breed- 

 ing-season, and is therefore in some way sexual."^ But what shall 

 we say about the harsh screams of, for instance, some kinds of 

 macaws; have these birds as bad taste for musical sounds as they 

 apparently have for color, Judging by the inharmonious con- 

 trast of their bright yellow and blue plumage? It is indeed pos- 

 sible that without any advantage being thus gained, the loud 

 voices of many male birds may be the result of the inherited 

 effects of the continued use of their vocal organs, when excited 

 by the strong passions of love, jealousy and rage; but to this 

 point we shall recur when we treat of quadrupeds. 



We have as yet spoken only of the voice, but the males of vari- 

 ous birds practice, during their courtship, what may be called 



" The spoonbill (Platalae) 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 con- 

 stantly present, so that perhaps they are now tending towards 

 abortion. 



's 'Elements of Comp. Anat.' by R. Wagner, Bng. translat. 1845, p. 

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

 ish Birds,' 2nd edit. 1S45, vol. iii. p. 193. 



" C. L. Bonaparte, quoted in the 'Naturahst Library: Birds,' vol. 

 xiv. p. 126. 



» L. Lloyd, 'The Game Birds of Sweden,' &c., 1867, pp. 22, 81. 



" Jenr.er, 'Philosoph. Transactions,' 1824, p. 20. 



