THE MIGRATION OF BIRDS 



passes the winter, or over what stretches of sea and 

 land the Arctic Tern passes when journeying be- 

 tween its summer home in the Arctic seas and its 

 winter abode in the Antarctic wastes? The main 

 fact, however, that the great majority of birds of the 

 Northern Hemisphere go south in autumn and re- 

 turn in spring, is well known. 



Moulting. — By the time the young are able to care 

 for themselves the plumage of the hard-working 

 parents is worn and frayed and a new suit of feathers 

 becomes necessary. They do not acquire this all 

 at once. The feathers drop out gradually from the 

 various feather tracts over the body, and their 

 places are at once taken by a new growth. While 

 this is going on the birds are less in evidence than at 

 other times. They keep out of sight and few song 

 notes are heard. Perhaps there is some irritation 

 and unpleasantness connected with moulting which 

 causes a dejection of spirit. 



With swimming water birds the wing quills dis- 

 appear nearly all at once and the birds are unable 

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