298 



ZOOLOGY 



Nest of the chimney swift. 



Hence a nest, in which to rest, is needed. The ostrich is an excep- 

 tion; it makes no nest but the male and the female take turns 

 in sitting on the eggs. Such birds as are immune from the attack 

 of enemies, either because of their isolation,, or their protective 



coloration (as the puffins, gulls^ 

 and terns), build a rough nest 

 among the rocks or on the 

 beach. The eggs, especially 

 those of the tern, are marked 

 and colored so as to be al- 

 most indistinguishable from 

 the rocks or sand on which 

 they rest. Other birds have 

 made the nest a home and a 

 place of refuge as well as a 

 place to hatch the eggs. Such 

 is the nest of the woodpecker 

 in the hollow tree and the 

 hanging nest of the oriole. 

 Some nests which might be easily seen because of their location 

 are often rendered inconspicuous by the builders; for example, 

 the lichen-covered nest of the humming birds. 



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 

 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. 



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- 

 gations undertaken by the U.S. Department of Agriculture (Divi- 

 sion of Biological Survey) show that a surprisingly large number 



