MIGRATION IN THE BRITISH ISLANDS. 249 



and flowing is not voluntary, although Mr. Cordeaux 

 appears to be of the opinion that it is. The neces- 

 sities accruing in past ages, and .handed down as 

 hereditary impulse, may also be a minor cause. 



Whilst the latter part of all this spring migration 

 is going on amongst birds that have either wintered 

 with us, or only left our shores to seek more genial 

 winter quarters in the immediate neighbourhood of 

 the continent, the regular northern migration of 

 birds from the far south, from the Mediterranean 

 basin and Africa, begins ; perhaps with the advent 

 of such birds as Wheatears {Saxicola aniantlie), 

 ChifFchaffs {PhijUoscopus rufus), and Woodcocks 

 (ScoIopcLv Tusticola), tow^ards the end of March, 

 although instances are on record where a few avant 

 couriered of the former species have been remarked 

 in the north of England during the last week in 

 February. With the advent of April, Migration 

 becomes much more intense ; as the month pro- 

 gresses species after species pours in from the 

 South : delicate Warblers, Redstarts, the Cuckoo, 

 the Wryneck, all the British Hirundines, Tree 

 Pipits, and so on ; together with a steadily increasing 

 stream of Waders, including the Common Sand- 

 piper ; also various species of Terns. Less intensity 

 characterizes Migration of British individuals in 

 May, although a vast number of birds are passing 

 our islands during that period, on their way to the 

 Arctic regions. During this month the last batch 

 of our regular summer visitors make their appear- 

 ance, which includes the Garden Warbler, the 



