138 WITH THE U. S. NATURALISTS 



full growni, the entire family leaves the Arctic 

 and, several months later, it is found skirting the 

 edge of the Antarctic continent. 



** 'What its track is, over that eleven thousand 

 miles of intervening space, no one knows. A few 

 scattered individuals have been noted along the 

 United States coast south as far as Long Island, 

 but the great flocks of thousands and thousands of 

 these Terns have not yet told us of their route or 

 time schedule. All we know is that they spend 

 about fourteen weeks in the Arctic and eighteen 

 weeks in the Antarctic, which gives them only 

 ten weeks to fly from Pole to Pole, twice a year.' 

 The Arctic Tern has twenty-four hours of day- 

 light for seven months of the year, and, during the 

 other four months, it will average twice as much 

 daylight as dark." 



''Is it a big bird?" asked the pot-hunter. 



"Much like the Common Tern," was the reply; 

 "about the only way that you can distinguish it, 

 at a distance, is that the tail is longer." 



"Yo' say," the old man continued, evidently 

 interested in this movement of birds, for it bore 

 indirectly on what had been his trade all his life, 

 "that it ain't weather, an' it ain't food which 

 starts birds migratin'. What is it?" 



