THE LIGHTHOUSE AT 



HELIGOLAND ON 

 A MIGRATION NIGHT 



CHAPTER XX. 



THE MIGRATION OF BIRDS. 



Hybernation of Birds Migration of Birds Reed-warblers Origin of 

 Migration Transvaal Warblers The Mammoth Age Insect Life 

 Lines of Migration Heligoland and 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 realise the fact that no longer ago 

 than towards the close of the last century the belief in 

 the hybernation of swallows was held by many ornitholo- 

 gists. That certain species of mammals spend the winter 

 in a torpid state is proved beyond all possibility of doubt ; 

 but there is no evidence of the hybernation of any species 

 of birds. Never was theory founded on more flimsy 

 substratum of supposed facts, or supported by weaker 

 logical argument. Swallows made their appearance in 



