36 THE MIGRATION OP BIRDS 



to a lesser extent the south-east coasts of 

 Britain ? 



Coasting undoubtedly exists ; birds, day migrants 

 especially, may be observed following coastlines 

 in steady flight, though a mile or less inland no 

 passage is visible. On the North Norfolk coast 

 I have seen little parties of swallows passing along 

 the shore in spring, coasting slowly but steadily 

 from east to west. All day long and almost every 

 day for more than a week this steady flight was 

 continued, though I never saw any passing within 

 sight more than a few yards out at sea, nor any at 

 all more than a few hundred yards inland. Evidence 

 which cannot be refuted shows that this habit of 

 coasting is general, though a deeply indented bay, 

 an estuary or strait, is usually crossed, and by no 

 means always at the narrowest point. The same 

 careful observations prove that both narrow and 

 wide river valleys are followed by migrating birds 

 in greater numbers than are ever observed passing 

 beyond the limits of these valleys. 



Seebohm's experience in Siberia led him to doubt 

 the existence of routes, but his later studies of 

 migration in autumn at Arcachon and in spring at 

 Biarritz, caused him to modify his ideas. He found 

 a gentle but continuous stream of migrants follow- 

 ing the coast of the Bay of Biscay, arriving from 

 over the Pyrenees on their northward journey, 



