VI 



BUCEROTIDAE 



39 



the unwieldy body acting as a great drag, though counterbalanced 

 by the pneumaticity, or air-containing nature of the bones, which 

 is perhaps greater in Hornbills than in any other birds. On the 

 wing a sound is generally produced like that of a steam-engine, 



FIG. 82. Hornbill. Dichoceros bicornis. Female and young. (From Malay Archipelago.) 



possibly due to the open nature of the quills ; but RTiinoplax, 

 JBerenicornis, Anorliinus, and Anthracoceros maldbaricus are said 

 to fly noiselessly. In some species the wing-action is regular ; 

 in others, rapid strokes alternate with sailing movements on out- 

 spread pinions ; the head is usually drawn in and the tail depressed ; 

 while flocks proceed in single file. Individuals alight heavily, and 



