THE LIGHTHOUSE AT 



HELIGOLAND ON 

 A MIGRATION NIGHT. 



CHAPTER XX. 



Hybernation of birds Migration of birds Reed-warblers Origin of migration 

 Transvaal warblers The Mammoth age Insect life Lines of migration 

 Heligoland Its ornithologists Variety of birds Wind and weather The 

 throstle-bushes Migration by sight Order of migration Stray migrants 

 The yellow-browed warbler Migration on Heligoland Skylarks Migratory 

 instincts Other facts of migration. 



IT is very difficult to reali-e the fact that not longer ago 

 than towards the close of the last century the belief in the 

 hibernation of swallows was held by many ornithologists. 

 That certain species of mammals spend the winter in a 

 torpid state is proved beyond all possibility of doubt; but 



