132 



The Bird 



cular as that of the Hoatzin, yet there must be powerful 

 movements of the walls, for the mice and birds are de- 

 nuded of hair and feathers and even the bones are in 

 some way removed from the body, and all are ejected 

 in a neat oval ball. 



If we find some hollow tree where an owl has its 



FIG. 103. Keel of Hoatzin, repressed by crop. 



regular sleeping-place, many of these pellets may be 

 found on the ground below, showing the results of each 

 night's hunting. The skulls in them are often in such 

 perfect condition that the species of rodents may be 

 identified. Besides allowing the bird conveniently to get 

 rid of the indigestible portions of its food, this habit 

 seems to be necessary to the health of the bird. In 



