CIRCUMPOLAR BIRDS 237 



Arctic regions to breed, not by thousands, but by millions. 

 The cause of this migration is to be found in the lavish 

 prodigality with which Nature has provided food. Seed- 

 or fruit-eating birds find an immediate and abundant 

 supply of cranberries, crowberries, and other ground fruit, 

 which have remained frozen during the long winter, and 

 are accessible the moment the snow has melted ; whilst 

 insect-eating birds have only to open their mouths to fill 

 them with mosquitoes. 



Of the 1 10 species which we obtained, the following are 

 circumpolar birds, breeding both in the eastern and western 

 hemispheres, being nearly one-third of the total number : — 



Osprey. Sanderling. 



Peregrine Falcon. Shoveller Duck. 



Snowy Owl. Pintail Duck. 



Short-eared Owl. Scaup Duck. 



Raven. Golden-eyed Duck 



Pine Grosbeak. Long-tailed Duck. 



Mealy Redpoll. Goosander. 



Lapland Bunting. Red-breasted Merganser. 



Snow Bunting. Arctic Tern. 



Shore-lark. Great Black-backed Gull. 



Bohemian Waxwing. Glaucous Gull. 



Sand Martin. Richardson's Skua. 



Willow-grouse. Buffon's Skua. 



Grey Plover. Red-throated Diver, 



Red-necked Phalarope. Black-throated Diver. 

 Dunlin. 



It will be observed that more than half of these species 

 are water birds, showing that the communication between 

 the Palaearctic and the Nearctic regions has been one of 

 water rather than of land. 



The following species are confined to the continents of 

 Europe and Asia, and range throughout the Arctic regions 

 of the eastern hemisphere from the North Cape to Bering's 

 Strait. A few of these are occasionally found in Greenland 

 and in Alaska, but are not found in the intermediate or 

 Nearctic regions, though many of them are there repre- 



