SOME QUESTIONS CONCERNING MIGRATION 



WE have stated, in the preceding chapter, some of the 

 general facts regarding Bird-Migration. These 

 lead on to a series of extremely interesting questions which 

 must be answered very tentatively until more data are 

 collected and critically scrutinised. At the same time, they 

 are not so far from solution as some deeper problems which 

 we propose to discuss in a later chapter. 



Since migration, as we have seen, implies an alternation 

 between a relatively colder breeding-place and a relatively 

 warmer wintering and resting-place, the general trend of 

 the journey ings must be from north to south, and back 

 again. But this picture is far too simple. The autumnal 

 north to south flight may end up with a great sweep to the 

 east, and in the north of Europe there is a very important 

 movement from east to west, sometimes with a final sweep 

 towards the south. 



" On dark autumn nights," Gatke says, " the sky is often 

 completely obscured by vast multitudes of plovers, curlews, 

 godwits, oyster-catchers, greenshanks, sandpipers, and 

 many other less vociferous species, such as larks and 

 thrushes, whose voices, resonant from afar, proclaim 

 clearly through the stillness of the night from what direc- 

 tion in the sky they are arriving, while the notes of the 

 departing travellers, gradually growing fainter and fainter, 

 announce in a manner equally distinct in what direction 

 they are continuing their journey. The whole flight proceeds, 



