SOME QUESTIONS CONCERNING MIGRATION 77 



without pause or change, in one incessant stream from east 

 to west." 



Hosts of birds gather in Autumn from the plains of 

 Russia and Finland, and pass along the southern shores of 

 the Baltic to Holland or the like, where the direction is 

 turned southwards. Certain contingents seem to follow 

 the valleys of the Rhine and Rhone, thus finding their way 

 to the Mediterranean, and across that to North Africa. 

 Other contingents seem to follow a coast route, crossing, 

 it may be, by Heligoland to the South of England, and 

 thence across to France and Portugal, but finally landing, 

 like the others, in North Africa. 



For some birds there is a considerable body of evidence 

 as to the routes followed. The common swallow, for 

 instance, seems on the whole to fly north and south. Large 

 numbers are seen in Autumn making their way down the 

 west coast of Africa, perhaps reaching the Cape ; those 

 from Eastern Europe are said to work their way southwards 

 by the Nile Valley. Corresponding species or varieties 

 in North America seem to fly to Brazil, and in North Asia 

 to Burmah. 



In illustration of a north to south movement, Gatke 

 cites the case of the Red-Spotted Bluethroat. Those that 

 breed in Norway are supposed to winter in North-East 

 Africa ; those that breed in Kamchatka are supposed to 

 winter in South Asia. That those moving from Norway 

 southward do not veer to the west, is indicated by the 

 absence of the bird from France and Spain and its great 

 rarity in England. 



Gatke was very strongly of opinion that the vernal 

 flight was more direct than the autumnal. Of the birds 

 that pass through Heligoland in Autumn, not more than 

 half, he said, return by that route in Spring. The others 

 cut across. Indeed, as Gatke put it, if the autumnal flight 



