THE BIRD STUDY BOOK 



preferred route and their time schedule. The Arctic 

 Terns arrive in the Far North about June fifteenth 

 and leave about August twenty-fifth, thus staying 

 fourteen weeks at the nesting site. They probably 

 spend a few weeks longer in the winter than in the 

 summer home, and this would leave theiji scarcely 

 twenty weeks for the round trip of twenty-two thou- 

 sand miles. Not less than one hundred and fifty miles 

 in a straight line must be their daily task, and this is 

 undoubtedly multiplied several times by their zigzag 

 twistings and turnings in pursuit of food. 



" The Arctic Tern has more hours of daylight and 

 sunlight than any other animal on the globe. At the 

 most northern nesting site the midnight sun has al- 

 ready appeared before the birds' arrival, and it never 

 sets during their entire stay at the breeding grounds. 

 During two months of their sojourn in the Antarctic 

 the birds do not see a sunset, and for the rest of the 

 time the sun dips only a little way below the horizon 

 and broad daylight is continuous. The birds, there- 

 fore, have twenty-four hours of daylight for at least 

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