146 THE MIGRATIONS OF BIRDS 



Alaska now differ sufficiently in color from Siberian 

 stock to enable them to be distinguished as sub- 

 species. This indicates long residence, yet we find 

 them following a perilous migration route across the 

 stormy, often fog-bound waters of Bering Sea to an 

 Old World winter home, when a safer route to the 

 south in the New World is open to them. Still more 

 intriguing and exciting to the imagination are the 

 birds that nest in Alaska, or in Siberia, and migrate 

 south across the open sea to winter in the islands of 

 the Pacific. From the American side these are 

 mainly water-birds whose movements will be dis- 

 cussed in another connection later. 



Migration routes in Europe have been worked out 

 in considerable detail, while those of Asia have been 

 indicated, but are less certainly known. A hasty 

 review will give some of the interesting points con- 

 cerning the main channels. 



To begin in the west — there is a broad zone of 

 flight that extends from the Arctic islands of Spitz- 

 bergen and Nova Zembla south, by way of the Scan- 

 dinavian peninsula, to the British Isles, a line that 

 receives certain tributary flight from Greenland and 

 Iceland. In England lines of flight extend along the 

 coasts, carrying large numbers of birds, while others 

 spread back inland throughout the island. 



Another broad line is supposed to cross from the 

 shores of the White Sea in Russia to Holland, or to 



