THE STRUCTURE AND ACTIVITIES OF BIRDS 345 



feathers. Besides this general function beaks are used in many 

 different ways: that of the woodpecker is chisel-shaped and 

 fitted for digging into the wood of trees ; the beak of the sparrow 

 that eats seeds is short and thick for crushing its food ; insect- 

 eating birds, like the thrush, possess beaks that are longer and 

 not so strong; birds, like the swift, that catch insects in the 





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Fig. 224. — Nest and eggs of the wood pewee. The nest was built on a hori- 

 zontal branch of a tree 15 feet from the ground. (Photo, by Hegner.) 



air have small beaks but very capacious mouths ; wading birds 

 possess long beaks for obtaining food under water and in the 

 mud ; and birds of prey are provided with strong, curved beaks 

 for tearing flesh. These are but a few of the many different 

 forms and uses that might be described. 



Birds are Warm-blooded Animals. — The feathers are of the 

 utmost importance to the bird, since flight is impossible without 

 them. While this is their most obvious function, there are sev- 

 eral others just as important. Birds and mammals are warm- 



