188 



orR GREATEST TR.WELERS 



MAP SHOWING THE EVOLUTION OF THE 



PRESENT MIGRATION ROUTE OE THE 



GOLDEN PLOVER (SEE 



PAGE 187) 



Golden plovers in considerable numbers 

 fly each fall the 2,400 miles across an 

 islandless sea from Alaska to Hawaii, 

 spend the winter there, and fly back 

 again the next spring to nest in Alaska. 

 But how did they first find their way to 

 Hawaii? 



It is not to be supposed that any birds 

 would deliberately strike out over un- 

 known seas hunting for a new winter 

 home. It is scarcely more probable that, 

 even if a large flock was caught in a 

 storm and carried far out of its course 

 to the Hawaiian shores, the birds would 

 change in a single season habits of count- 

 less generations and start at once a radi- 

 cally new migration route. It has already 

 been said that present migration routes 

 are evolutions — age-long modifications of 

 other routes. The problem, then, is to 

 find some migration route from which 

 the golden plover's present Hawaiian- 

 Alaskan route could have been easily 

 and naturally derived. 



The bird breeds on the northern shores 

 of eastern Siberia, from the Liakof Is- 

 lands to Bering Strait, and on the Alaska 

 side of the strait south to the northern 



base of the .Alaska peninsula (page 189). 

 It winters on the mainland of southeast- 

 ern Asia, in the eastern half of .Australia, 

 and throughout the islands of Oceanica, 

 from Formosa and the Liu Kiu Islands 

 on the northwest to the Low Archipelago 

 in the southeast. 



The breeding range has an east-and- 

 west extension of about 1,700 miles, 

 while the winter home extends nearly 

 half around the globe — 10,000 miles — 

 from India to the Low Archipelago. 

 Undoubtedly the original migration route 

 was approximately north and south, be- 

 tween the nests in Siberia and the winter 

 resorts in southern Asia. In the course 

 of time the species spread eastward in 

 the winter to Australia, to the islands 

 along the eastern coast of Asia, and 

 throughout Oceanica, while at the same 

 time the breeding range was extended 

 eastward across Bering Strait to Alaska. 



If all these extensions took place be- 

 fore there was any cutting ofif of corners 

 in the migration route, then at this stage 

 of development the Alaska-breeding birds 

 were journeying over 11,000 miles (page 

 189, No. i) to reach the Low Archipel- 

 ago, distant only a little more than 5,000 

 miles in an air-line. 



It is fair to suppose that early in the 

 course of the eastward extension among 

 the Pacific islands, the plover began to 

 shorten the roundabout journey by flights 

 from the northern islands to eastern 

 Asia, and finally to Japan (No. 2). The 

 most northern island is Palmyra, and the 

 flight from there westward to the nearest 

 of the Marshall Islands is about 2,000 

 miles ; thence a 3,000-mile journey, with 

 several possible rests, brings the birds to 

 Japan. 



It is easily possible that birds accus- 

 tomed to this 5,000-mile flight might be 

 driven by storms a thousand miles out of 

 their course and discover Hawaii. When 

 from Hawaii they attempted to reach 

 Japan (No. 3) they would find a chain of 

 islands stretching for 1,700 miles in the 

 desired direction, and the final flight of 

 2,000 miles from the last of these — the 

 Midway Islands — to Japan would be no 

 longer than previous flights to which they 

 had become accustomed. 



Having- once learned the route from 



