COMMON SHELD-DUCK. 357 



colour ; the head and neck brown ; chin and front of the 

 neck white ; interscapulars and wings brown ; wing-coverts 

 white ; inner secondaries white, edged with chestnut ; 

 primaries black ; speculum becoming green ; all the under 

 surface white ; legs flesh-colour. The young birds do not 

 breed till they are two years old. 



The markings of the nestling are like those of the pre- 

 ceding species, but the brown is of a darker tone, and the 

 white of the under parts is purer. 



The organ of voice in the Sheld-Duck is distinguished 

 from that of any other genus. The trachea, or windpipe, 

 is about ten inches long, nearly uniform in size throughout 

 its length, except towards the bottom, where, for about one 

 inch, it is much smaller. On each side of the bone of 

 divarication forming the bottom of the tube, there is a 

 globular, hollow, bony protuberance ; that on the one side 

 being as large again as the one on the other. The bone is 

 thin, and so flexible when in its moist and natural state as 

 readily to become indented on pressure. The representation 

 given below is only a little smaller than the natural size. 

 The tube below each enlargement, going off, one to each 

 lobe of the lungs, presents nothing remarkable. 



