Chap. XIIL] VOCAL MUSIC. . 53 



males than in the females ; but with this slight exception 

 there is no difference in the vocal organs of the two sexes, 

 although the males of most species sing so much better 

 and more continuously than the females. 



It is remarkable that only small birds properly sing. 

 The Australian genus Menura, however, must be ex- 

 cepted; for the Menura Alberti, which is about the size of 

 a half-grown turkey, not only mocks other birds, but " its 

 own whistle is exceedingly beautiful and vai-ied." The 

 males congregate and form " corrohorying places," where 

 they sing, raising and spreading their tails like peacocks 

 and drooping their wings. '° It is also remarkable that 

 the birds which sing are rarely decorated with brilliant 

 colors or other ornaments. Of our British birds, except- 

 ing the bullfinch and goldfinch, the best songsters are 

 plain-colored. The king-fisher, bee-eater, roller, hoopee, 

 woodpeckers, etc., utter harsh ci'ies ; and the brilliant 

 birds of the tropics are hardly ever songsters," Hence 

 bright colors and the power of song seem to replace each 

 other. We can perceive that if the plumage did not vary 

 in brightness, or if bright colors were dangerous to the 

 species, other means would have to be employed to charm 

 the females; and the voice being rendered melodious 

 would ofier one such means. 



In some birds the vocal organs differ greatly in the 

 two sexes. In the Tetrao cupido (Fig. 39) the male has 

 two bare, orange-colored sacs, one on each side of the 

 neck ; and these are largely inflated when the male, dur- 

 ing the breeding-season, makes a curious hollow sound, 

 audible at a great distance. Audubon proved that the 

 sound was intimately connected with this apparatus, 



39 Gould, 'Hand-book to the Birds of Australia,' vol. i. 1865, pp. 308- 

 310. See also Mr. T. W. Wood in the 'Student,' April, 1870, p. 125. 



^^ See remarks to this eflfect in Gould's ' Introduction to the Trochi- 

 lidae,' 1861, p. 22. 



