l6 SEA-BIRDS 



With the exception of a few gulls, sea-birds entirely desert the 

 arctic regions bordering Baffin's Bay and Davis Strait in October and 

 do not return until April. From no other part of the northern hemi- 

 sphere is there so great a withdrawal of sea-birds to avoid a period of 

 inhospitable climate. 



The eastern arctic islands — Jan Mayen, Bear Island and Spits- 

 bergen, Franz Josef Land and Novaya Zemlya, which lie across the 

 Polar Basin where it abuts on the North Atlantic, have a very similar 

 breeding sea-bird community to that of Greenland, though none has 

 so many members. We can best make this comparison in the form of 

 a table, adding columns for the Canadian Arctic, Arctic Russia-in- 

 Europe and Arctic Norway. (Page 15.) 



We now come to the seabird community of Iceland, Faeroe, the 

 British Isles, Scandinavia, the Baltic, and the North Sea and English 

 Channel. This community is very homogeneous, considering the range 

 of latitude over which it is spread, though there are some members 

 which do not reach the south end of this range and a few which do 

 not reach the north. Among the species which are found over almost 

 the entire twenty degrees of latitude are the Manx shearwater, the 

 storm-petrel Hydrobates pelagicus, the gannet, the shag Phalacrocorax 

 aristotelis, the cormorant, the herring-gull, the lesser blackback 

 Larus fuscus, the great blackback, the black-headed gull L. ridibundus, 

 the kittiwake, the common and arctic terns, the razorbill, the guillemot, 

 and the puffin. Species which occupy the more northerly parts of 

 this temperate European stretch incUide the great skua Catharacta 

 skua, and Leach's petrel (Iceland, the Faeroes and Britain only), the 

 fulmar, the arctic skua, and the black guillemot. The glaucous gull, 

 little auk and Briinnich's guillemot breed (in this part of the Atlantic) 

 only in Iceland. 



There is a central group of sea-birds which breeds neither as far 

 north as Iceland nor as far south as Atlantic France; this is headed 

 by the common gull Larus canus, and includes also the little gull L. 

 minutus; its other members are terns, the whiskered tern Chlidonias 

 hybrida (only casual, in Holland), the black tern C. nigra, the white- 

 winged black tern C leucoptera (casual only), the gull-billed tern and 

 the Caspian tern. The populations of all these terns are low, and only 

 two of them (black and gull-billed) have recently bred in Britain, 

 and that casually; their headquarters lie between Holland and the 

 South Baltic. The Baltic Sea, though it has as many breeding terns 

 and gulls as any other part of this stretch of the east Atlantic, lacks 



Plate 2. Storm petrel incubating in a rock-crevice on Skokholm, Pembrokeshire 



