BIRDS IN SEVERE FROSTS. 377 



in a dry state, they soon die. * It is therefore easy 

 to see how impossible it would be for such aquatic 

 fowl to remain in a district where the springs were 

 sealed by frost. In our own land they can however 

 always betake themselves to the sea coast, and so 

 obtain both food and water ; but this cannot be in the 

 heart of a great continent like Asia, or North America, 

 where the northern seas themselves become ice-bound, 

 and where the land for vast distances in every direc- 

 tion is converted into a , perfectly dry field of snow 

 or ice. It is therefore clear that the only resource is 

 a flight towards the south. 



This therefore evidently explains the motive cause 

 of the vast migrations of fowl which take place from 

 the polar regions during autumn, in both these con- 

 tinents: while the return flights of these migrants in 

 spring are the result of the natural impulse which 

 causes them to seek the land of their birth and assemble 

 in multitudes at their breeding grounds in the far north 

 the moment the break-up of the ice releases the waters 

 from the winter's bonds. We have gone into the 

 subject of these great migrations to and from the cir- 

 cumpolar regions with some detail in our arctic section, 

 and have there stated the reasons which lead us to 

 believe that the whole of the polar wilderness is used 

 by various kinds of birds as a nesting place on account 

 of its security from the interference of enemies while 

 rearing their young. This view is supported by very 

 high authority of which we shall here quote merely a 

 single example: 



* These pans should be quite shallow, say not exceeding about half an 

 inch in depth, and the water should just barely cover the food. They 

 should be used in the cases of all aquatic birds, ornamental water-fowl 

 etc., when reared by hand. 



