84 GEOGRAPHICAL DISTRIBUTION 



Podiceps nigricollis. 



The breeding range of the Eared Grebe extends across Europe 

 and Asia to the Western States, and probably occurs in Alaska. 

 To the south it extends far into the Tropics both in Africa and 

 America. 



Of these four species the Cormorant may be regarded as sub- 

 arctic, subtropic, and tropic in its breeding range, the Wheatear 

 and the Magpie as arctic, subarctic, and subtropic, and the Grebe 

 as subarctic, subtropic, and tropic. 



NORTH ATLANTIC SPECIES. 



There are twenty species of British Birds which may be 

 regarded as North Atlantic species, inasmuch as they breed for 

 the most part on islands in the North Atlantic Ocean, and occa- 

 sionally on cliffs on both its American and European shores, but 

 are unknown in the Pacific Ocean. Six of these only breed in an 

 arctic climate : 



Alca alle. 



Alca troile brunnichi. 



Colymbus glacialis. 



Anser brachyrhynchus. 



Bernicla leucopsis. 



Bernicla brenta. 



Five others breed not only in an arctic climate, but also in a 

 subarctic : 



Larus argentatus. 

 Alca torda. 

 Alca grylle. 

 Fratercula arctica, 

 Somateria mollissima. 



Four species are only known to breed in a subarctic climate: 



Alca impennis (extinct). 

 Stercorarius catarrhactes. 

 Procellaria pelagica. 

 Sula bassana. 



