9+ 



THE MIGRATION OF BRITISH BIRDS 



Before making any comment upon the species tabu- 

 lated above, it is necessary for us to deal with another 

 group of birds, a study of whose geographical distri- 

 bution and migratory movements will assist us, I think, 

 in demonstrating the philosophy of a very intricate and 

 hitherto inexplicable phenomenon : viz. the absence of 

 certain species from the British Islands which are 

 common and widely dispersed in continental areas 

 almost within sight of them. Various ingenious sug- 

 gestions have been made by naturalists in their attempts 

 to explain what looks like an anomaly of distribution, 

 but, as I hope presently to show, the curious fact is 

 perfectly regular and conforms in every way to the 

 known laws of avian dispersal. This group will be com- 

 posed of species whose northern range in the cxtrcuie 

 zuest of continental Europe, or in all Europe, does not 

 reach the Briti.sh Islands, or say latitude 50°. 



