DISTANCES TRAVELLED BY BIRDS 81 



depart, in a single season, from ancient habits and 

 carve out an entirely new migration route. Probably 

 the origin of the route is as follows. The bird breeds 

 on the northern shores of eastern Siberia from the 

 Liakof Islands to Behring Strait, and on the Alaskan 

 side south to the northern base of the Alaska 

 peninsula. It winters on the mainland of south- 

 eastern Asia, in eastern Australia, and throughout 

 the Oceanic Islands from Formosa and the Liu 

 Kiu Islands on the north-west to the Low Archi- 

 pelago in the south-east. 



It is fairly .certain that the original route would 

 be roughly north and south, between Siberia and 

 southern Asia. In time the species spread eastward 

 in winter, to Australia and to islands farther east, 

 whilst the breeding area extended to Alaska. If 

 these extensions took place before any cutting off 

 of corners in the route, Alaska birds would travel 

 11,000 miles to reach the Low Archipelago, only 

 5000 miles in a direct air-route (No. 1). Probably 

 shortening began early among the Pacific islands, 

 from the northern islands to the Asiatic coast, and 

 finally to Japan (No. 2). From Palmyra the flight 

 to the nearest of the Marshall Islands is 2000 miles ; 

 thence a journey, provided with several possible 

 rests, of 3000 miles would bring them to Japan. A 

 thousand mile drift through strong winds might 

 cause the birds to reach Hawaii, whence they would 

 F 



