The Arctic Tern 



THE ARCTIC Tern is truly named, for it enjoys a circumpolar 

 distribution, and it breeds as far north as land is to be found, even to 

 Grinnell and Peary Lands, in Latitude 82 °. Because of favoring con- 

 ditions, or perhaps because of ancient habit, established before the frigid 

 zone was available as a nesting site, some few of the species still linger 

 along the coast of Maine; and they have nested off the coast of Massa- 

 chusetts within historic times. On the Pacific side, where milder tem- 

 peratures prevail, the Arctic Tern does not breed further south than 

 Glacier Bay and some of the Aleutian Islands. In migration, therefore, 

 these birds are sure to occur regularly off our coasts, but our records are 

 meager, and it is not certain that they may be expected with any regu- 

 larity inshore. It is significant, however, that all records of coastal 

 movement cease with Long Island on the Atlantic side, and with southern 

 California on the Pacific. 



The winter range of the Arctic Tern was for years shrouded in mys- 

 tery. Finally, in 1904, these birds were discovered by the "Scotia" 

 expedition to be present in immense numbers on the Weddell Sea, in 

 Latitude 72 ° to 74 South. This particular waste of Antarctic waters 

 is, therefore, in all probability, the focal point of the entire species; and 

 in reaching this spot the birds must follow fly-lines across the open ocean, 

 for there are few South American records of its occurrence. How romantic 

 and how daring this annual flight from pole to pole (approximately speak- 

 ing) really is, only the imagination may picture. At any rate, we know 

 that Sterna paradiscea is the holder of the world's long distance record 

 for migratory flight. 



Of the further implications of this movement Mr. Wells W. Cooke 1 

 says: "The Arctic Terns arrive in the far north about June 15 and 

 leave about August 25, thus staying 14 weeks at the nesting site. 

 They probably spend a few weeks longer in the winter than in the summer 

 home, and this would leave them scarcely 20 weeks for the round trip of 

 22,000 miles. Not less than 150 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 upon the globe. At the most northern nesting site the 

 midnight sun has already 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 have, therefore, 24 hours of daylight 

 for at least eight months in the year, and during the other four months 

 have considerably more daylight than darkness." 



1 Bird Migration. Bull. No. 185, U. S. Dept. of Agriculture. 1915, pp. 9 and ro. 



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