i88 THE FOOD OF ANIMALS 



highly specialized organs have been evolved from simpler struc- 

 tures, for nestling Crossbills still possess symmetrical beaks like 



Fig. 430. The Crossbill (Loxia cnnnrostrn] 



those of other birds, reminiscent, no doubt, of the ancestral con- 

 dition. 



OIL-BIRDS (STEATORNITHIDiE) 



We are apt to associate a markedly hooked beak with rapa- 

 cious habits, but notable exceptions to the rule are afforded by 

 Oil- Birds and Parrots. The Oil- Bird or Guacharo (Steatornis 

 Caripensis] inhabits caves in the northern parts of South America, 

 and possesses a strong hooked beak, mainly used, however, for 

 securing the fruits of the nectandra-tree. This is another case 

 of adaptation in a South American animal (see p. 86) for seizing 

 berries or other fruit growing on the end of slender stalks in- 

 capable of supporting any considerable weight, and the Oil- Bird, 

 which is about the size of a crow, feeds on these particular fruits 

 when it is on the wing. 



PARROTS (PSITTACI) 



The large and interesting group of Parrots presents many 

 interesting adaptations to the nature of the food, which chiefly 

 consists of fruits, seeds, and other parts of plants. The shape 

 of the curious hooked beak is familiar to everybody, but all may 



