268 THE MIGRATION OF BRITISH BIRDS 



at that season under precisely similar circumstances. 

 It would therefore be a most extraordinary thing indeed 

 if this bird visited Heligoland in autumn, for to reach 

 that island from its present normal limits of distribution 

 it would absolutely have to take a northern flight ! 

 Again, the Dotterel is said not to visit Malta in spring 

 but to pass regularly enough in autumn. Now the 

 Dotterel migrates very rapidly in spring, its migration 

 not lasting much more than a month ; in autumn, how- 

 ever, as is customary with many species, it migrates 

 more leisurely, the passage extending over four months, 

 and in fact finds time to visit places it had to pass very 

 quickly on its flight north. The Turtle Dove is commoner 

 in spring at Heligoland than in autumn ; the Whimbrel 

 passes the British Islands in greater numbers presumably 

 in spring than in autumn. But it has been remarked 

 that the latter bird flies much higher in autumn, 

 and consequently is disposed to alight less. The same 

 remarks will probably apply to the Turtle Dove. In 

 the latter cases, it will be remarked, a complete reversion 

 of route has not been suggested. We might with equal 

 propriety say that species of which individuals abnor- 

 mall)" appear in our islands only in autumn or spring 

 change their route according to season. The Little 

 Bunting, the Rock Thrush, and the Yellow-browed 

 Warbler are cases in point. 



The migration of birds in autumn over, from, and to 

 the British Islands extends over a period of quite five 

 months. It begins in July and continues to November 

 or even into the early part of December. Generally 

 speaking, the tendency of migration in autumn is 

 leisurely and more prolonged than in spring. The great 

 bulk of autumn migration takes place in September and 



