PREPARING FOR THE JOURNEY 



too small to raise them in the air. It is as though 

 their engines had become rusty from disuse. 



Not all the great bird travelers have such a 

 splendid engine as the Swallow. Some, indeed, 

 like the Sora or Carolina Rail, have such small 

 wings that it is difficult to understand Jhow they 

 fly from Canada to South America. But we 

 must remember that their bodies are light. It is 

 not so much the size of the engine as the size of 

 the train it draws that counts. The Humming- 

 bird's wings are not much wider and longer than 

 one's thumb, but they are large enough to carry 

 the bird's tiny body over thousands of miles. 



Everyone knows that birds' wings, or engines, 

 are made of feathers growing from a very light 

 but wonderfully strong frame of bones. Light- 

 ness and strength are indeed the main features of 

 the bird's wing. But even the strongest feathers 

 wear out. Then the engine must be repaired. 

 No bird wears a suit of feathers longer than one 

 year. The change is usually made in summer 

 after the family has left the nest and learned 

 to take care of itself. Then the old and worn 

 13 



