MIGRATION IN THE BRITISH ISIANDS. 263 



US." Now this is an intensely interesting fact, and 

 confirms very strongly our opinion above expressed, 

 that in some cases at least the birds flying south 

 are merely passing our coasts on passage from 

 North-Western Europe ; for among the species 

 that struck on the N.W. side in this instance 

 was the Redwing, clearly demonstrating that in this 

 case the northern stream was on its normal way 

 south via the British coasts, and was not composed 

 of our own birds leaving us to winter further south. 

 Whinchats and Willow Wrens were also in the 

 stream — species the individuals of which breed 

 in Scotland normally leave that district, say' in 

 September. A similar Cross Migration is also 

 apparent during autumn in the south-western 

 portions of the North Sea. 



We have also the same facts presented to us of 

 Migrants waiting for favourable winds; and on the 

 south coast of England the same double streams 

 of birds, one passing nearly due east to the Straits 

 of Dover, composed of various kinds of summer 

 migrants on their way south, passed by another 

 stream of hardier birds coming into our islands for 

 the winter, and passing as nearly due west. 



It remains for us now to notice the various Winter 

 Migrations passing from the continent to our islands, 

 or Local Movements among the birds wintering with 

 us. Changes of temperature are the great initiating 

 causes of these minor waves of Nomadic Migration, 

 and some of the rushes which then occur are both 

 interesting and important. Thus severe weather in 



