282 BIRD BEHAVIOUR 



thus, in the common drake, though he can make 

 a much louder noise than the Muscovy, the quack 

 sounds exactly as if he had an extremely bad 

 cold. Drakes, indeed, can seldom produce so full 

 a sound as the ducks, and the voices of the 

 two sexes are not interchangeable as they are in 

 some other birds most of my readers must have 

 come across a crowing hen or a singing female 

 Canary, and every one knows the cock can cluck 

 and cackle just as much as the hen. 



The voice of birds is produced in the syrinx, a 

 special vocal organ situated at the base of the 

 windpipe just at its bifurcation to enter the lungs, 

 and it is here in the drakes that the " drum " is 

 developed where it exists. Where it is present but 

 very small, as in the Ruddy Sheldrake (Casarca 

 rutila), the drake may have as strong a voice as the 

 duck, and where it is absent, as in the tiny Cotton- 

 Teal (Nettopus coromandelianus) the drake's note 

 may be stronger, the male in this little Duck 

 cackling loudly, while the female only squeaks like 

 a duckling. In the Tree-ducks there is no bulb, 

 and both sexes have a strong voice, uttering a 

 whistling cackle or a subdued twitter ; in fact, 

 they can modify their voices almost like the singing 

 Passerine birds. 



In the latter the vocal muscles developed at the 

 base of the windpipe are particularly strong, but 

 the same development is found in the Crows, which 

 are not commonly reckoned as songsters, and in 

 one type of Passerine bird supposed to have a 



