1900.] F. Finn — Structure and Function of the Tracheal Bulb. 149 



With a bony bulb in trachea of male. 

 Name. Voice of Male. Voice of Female. 



Carina moschata. A panting hiss. A sharp quack. 



Aix galericulata. A snorting whistle (iveesh!) A quacking sneeze (atch!) 

 Ohenalopex segyp- 



tiacus. A husky chatter. A harsh barking quack. 



Eunetta falcata. A -whistling cry like a A quack five times repeat- 

 duckling's, ed. 

 Dafila acuta. A faint weak quack. A harsh single quack. 



With a partly bony, partly membranous bulb in trachea of male. 



Bhodonessa cary- A melodious double call Not known ; but never 

 ophyllacea. (wugh-ah !) gives the male note, while 



the drake often calls. 

 Nyroca baeri. A faint low quack. A harsh croak (karr !) 



Nyroca africana. „ ,, 



Merganser castor. A harsh croak (liarr !) A short abrupt quack. 



Of course many more well-known cases could be given, but I have 

 in the above table merely given some, which being imperfectly or not at 

 all recorded, have attracted my special notice. Casarca rutila is an 

 exception proving the rule, since in this bird the tracheal bulb of the 

 male is, as above noted, singularly small, and there appears to be no 

 difference between the voice of the sexes in consequence. Authors in 

 describing the sexual difference in the voices of various Anatidse, often 

 speak as if the quack were common to both sexes, and another note 

 peculiar to the male alone. At other times no sexual distinction in 

 voice is mentioned, as in Hume's account of the Pintail {Dafila acuta) 

 " Game Birds of India," vol. iii, p. 193). The same explanation will, I 

 think, account for both errors, the birds having been studied from a 

 distance when in flocks, and the cries of the separate birds thus having 

 been confused. With regard to our two domestic ducks (Anas boschas 

 and Cairina moschata) the drakes seem quite incapable of giving the 

 duck's note, and vice versa, and I think the same rule will be found to 

 apply throughout. That there are certain species, like Nettopus coro- 

 mandelianus and CEdemia nigra, in which the male has no tracheal bulb 

 and yet gives a different call from the female, in no way invalidates the 

 importance of this structure in the others ; for the voices of male birds, 

 in the Gallinse and Passeres for instance, often differ from those of 

 females without any corresponding difference in anatomical structure. 

 The tracheal bulb in the Anatidse, where found, merely, in my opinion, 

 makes such difference necessary and permanent. 



