LETTERS 



MIGRANTS FLYING NORTH IN AUTUMN AT 

 DUNGENESS. 



To the Editors of British Birds. 



Sms, — Mr. Alexander's paper on migration [antea, p. 226) 

 is very interesting. I should be very glad if he or any ojf 

 your readers could explain what the birds that in late October 

 are flying northwards are about ? Are they making for 

 Dover, intending to cross to the Continent where the straits 

 are narrowest ? F. W. Headley. 



Haileybury College, March 4th, 1915. 



[Regarding Mr. Headley's question, any answer is bound 

 to be merely speculative. I do not for a moment beheve 

 that birds flying north along the Kentish coast from Dungeness 

 could be doing so with the purposeful object of crossing by 

 the shortest sea-passage, particularly seeing that some of 

 these birds had just arrived from across the Channel — from 

 Cape Grisnez or thereabouts ; these birds, if they re-crossed 

 from Dover, would have migrated round a circle. 



I should like to suggest that birds on migration in autumn 

 have no intention except to arrive at some customary 

 winter-quarters, or even, perhaps, only to move more or 

 less towards such quarters without an overpowering impulse 

 to go the whole way if circumstances happened to favour 

 their winter residence in some nearer (or further) locaUty. 

 Even the end of the journey is, I should say, partly deter- 

 mined bj^ circumstance ; the means of approaching that 

 end are probably determined almost entirely by the circum- 

 stance of the moment — direction and force of wind, food- 

 supply and other matters : thus the route followed in any 

 instance may easily become very circuitous and complicated. 

 At the same time, I am aware that there is a lot of evidence 

 to suggest that birds follow the same migratory routes year 

 after year with great precision. So that (without wishing 

 to dogmatize) I would suggest that migration is carried out 

 from generation to generation under a strong compulsion 

 of conservative custom (without which it would be mere 

 chabs) ; but whereas this might at any moment lead to 

 great disaster, the migrating birds have, perhaps in varying 

 degree, the power to modify this custom in such a waj^ as to 

 meet the circumstances of the moment. — H. G. Alexander.] 



