96 A BOOK OF BIRDS 



are extremely light, the bone being of the delicacy of filigree work, 

 and covered externally by the horny sheath. 



The nesting habits of the Hornbills are not less remarkable than 

 their beaks. After the eggs have been laid and the female begins 

 to sit, the male proceeds to plaster up the hole by which she 

 entered with mud, leaving a small aperture out of which she thrusts 

 her bill to receive her daily rations dutifully brought by her lord and 

 master. What is still more strange, this food is brought up from 

 his stomach enclosed in a membrane, or bag. She remains imprisoned 

 till the young are fledged. 



The HoMRAi HoRNBiLL (Plate XIX. fig. i), a Malayan species, 

 may serve as a good example of this curious group of birds. 



There is one extraordinary exception to the rule with regard to 

 the lightness of the structure of the beak, and this is furnished by the 

 Helmet Hornbill {Rhinoplax vigil) of the Malay countries. The 

 fore part of the great helmet which surmounts the beak of this bird 

 is of great thickness and exceeding hardness, so much so, that it is 

 greatly prized by Eastern artists, who make therefrom carved orna- 

 ments of various kinds, many of which are of great beauty. 



