304 THE VERTEBRATE ANIMALS 



Care of the Young. After the eggs have been hatched, the young 

 in most cases are quite dependent upon the parents for food. Most 

 young birds are prodigious eaters; as a result they grow very 

 rapidly. It has been estimated that a young robin eats two or 



Common tern (Sterna hirundo) and young, showing nesting and feeding habits. 

 From group at American Museum of Natural History. 



three times its own weight in worms every day. Many other young 

 birds, especially kingbirds, are rapacious insect eaters. In the case 

 of the pigeons and some other birds, food is swallowed by the mother, 

 partially digested in the crop, and then regurgitated into the mouths 

 of the young nestlings. 



Problem XL. How birds are of economic importance. (Lab- 

 oratory Manual, Prdb. XL.} 



Food of Birds. The food of birds makes them of the greatest 

 economic importance to our country. This is because of the rela- 

 tion of insects to agriculture. A large part of the diet of most of 

 our native birds includes insects harmful to vegetation. Investi- 



