COMB or KNOB-BILLED DUCK 73 



Association. The best observers almost all assert that the Comb Ducks travel 

 about in pairs or families, and only very rarely unite to form flocks. Larger com- 

 panies have, however, been seen in Nigeria (Hartert, 1886) and in Burma (E. W. 

 Oates, 1883), as well as in the Sudan (von Heuglin, 1873). E. H. Young (1899) tells us 

 that even when in flocks, the various pairs keep together, and when one bird has 

 been shot, its mate will often remain behind. This species does not associate com- 

 monly with other water-fowl, but sometimes they are found in company with Spur- 

 wings or White-faced Tree Ducks (von Heuglin, 1873; Bohm, 1885), or in India 

 with Ruddy Sheldrakes, the only fowl with which, says Hume, they ever closely 

 associate. 



Voice. In wild birds, and also in those kept in captivity, the voice is almost 

 wholly absent, Heinroth (1911) even maintaining that he never heard them utter 

 any sort of note. By most observers they are described as very silent birds. Von 

 Heuglin (1873) speaks of a tender, whispering note, uttered while on the wing. 

 According to Bohm (1885) the voice is very fine and thin. The testimony of two 

 well-known naturalists, however, is considerably at variance with the above. Legge 

 (1880) describes the note as a low, guttural, quack-like sound, between the voice of a 

 duck and a goose; and Baker (1908) heard them "uttering loud cries" which seemed 

 to him more like the notes of a goose than of a duck. A pair, whose nest he found, 

 used to herald his approach with "loud trumpeting calls" from perches high in a 

 tree. It is possible that the birds call only during the nesting season. 



In the male there is a very small left-sided diverticulum at the lower end of the 

 trachea which may affect the voice of this sex (Garrod, 1875). The trachea of the 

 female is simple. 



Food. The food of the Comb Ducks seems to be chiefly of a vegetable character 

 including both wild and cultivated rice. According to Hume and Marshall (1879) 

 they also swallow worms, larvae of water insects, small shells, fresh-water crusta- 

 ceans, and occasionally a tiny fish or two. The vegetable part of their diet consists 

 of grass, water weeds, and various kinds of seeds; in India, sometimes, a remarkably 

 hard quadrangular variety of water-grass seed. 



Courtship and Nesting. When the rains commence in India, the Comb Ducks 

 become active throughout the day and move about in pairs. The male, now ren- 

 dered conspicuous by his much enlarged nasal protuberance, and usually flying in 

 front, is distinguishable at a great distance (Hume and Marshall, 1879). From the 

 Berlin Gardens (Heinroth, 1911) comes the only available account of the courtship 

 of this species. The males in a very erect position approach the females with the 

 same continual dipping movement of the head and neck into the water that is com- 



