WALLED UP. 141 



observing the bird in its wild state. The hornbills 

 are kept in a special aviary, apart from all others, and 

 are the first birds of the sort ever brought to Europe. 



The strangest purpose, perhaps, to which the beak 

 of a bird is ever applied occurs in the use of it by 

 these very hornbills. These beaks are of such ample 

 proportions that, until we learn that they are the 

 merest shells of thin, horny substance, filled with light 

 cellular tissue, we may well wonder how the birds ever 

 manage to carry them, especially as, in addition to the 

 bulkiness of the real beaks, the upper mandible bears 

 above it a sort of annex, or supernumerary structure, 

 as large as the beak itself. 



Such a utensil — although it is used very dexter- 

 ously — is out of the question in nest-building, and 

 consequently the hornbill leaves that business to 

 birds with beaks of more manageable proportions. 

 A hollow tree is good enough for him, and when 

 he and his wife go house-hunting, in the spring of 

 the year, they are on the lookout for an apartment 

 of suitable proportions, with a doorway which, if too 

 small, they can enlarge for themselves. The situa- 

 tion must be secluded but lofty, and within con\'en- 

 ient distance of fruit-bearing trees. 



When a suitable abode is selected, Mrs. Hornbill 

 retires into the deepest recesses and gives herself up 

 to family cares, plucking from her own body the 

 feathers which make a soft bed for eggs and nestlings. 

 Henceforth she is at home to no one until her chil- 

 dren have grown large enough and strong enough to 

 leave their home, because, unable to fly or defend 



