418 MIGRATION 



considerable numbers, and were soon in full song. Newly 

 arrived parties were always silent, and sometimes the 

 hedges quite swarmed with these pretty little birds, 

 apparently tired and hungry after their migration, anxiously 

 searching the bushes for food, and very frequently taking 

 a short flight into the air to capture a gnat upon the wing. 



The marked difference between migration at Heli- 

 goland and migration on the shores of the Bay of Biscay 

 is, that at the former locality not a bird was to be seen in 

 unfavourable weather, but that when the wind was pro- 

 pitious birds came over with a rush, whilst at the latter 

 post of observation a gentle stream of migration seemed 

 always to be going on, in almost all weathers, from early 

 morn to late at night. The natural inference from such 

 observations is, that in the middle of a long land-journey 

 they simply travel slower in unfavourable weather, and 

 rest at night ; but when a sea-journey has to be made, 

 they wait for favourable wind and weather, and conse- 

 quently it often happens that, when the right time comes, 

 a crowd of birds has accumulated, which comes over en 

 masse, with what ornithologists call a " rush." 



Another result of my Bay of Biscay experience is, that 

 I must revoke my suggestions that too much has been 

 made of the great lines or routes of migration.^ I made 

 many excursions inland, both from Arcachon and from 

 Biarritz, but a very few miles from the coast took me out 

 of the range of migration. On the west coast of France, 

 both in spring and autumn, birds appeared to me to 

 migrate low, principally by day, and to follow the coast- 

 line. I am inclined to think that I must also recall the 

 doubts, formerly expressed, that birds follow ancient coast- 

 lines. The migration from the south of Denmark over 

 Heligoland to the coast of Lincolnshire seems to corre- 



* See p. 195 in Part I. 



