STRUCTURE AND SEA-BIRDS OF THE N. ATLANTIC I3 



It is in the Bay of Fundy, then, on the borders of the U.S. and 

 Canada (Maine and New Brunswick) that the northern birds really 

 begin. Here in burrows in the island rocks nest the southern elements 

 of the rather small Atlantic population of Leach's petrel Oceanodroma 

 leucorhoa. Here, too, are the representatives of the northern race of 

 double-crested cormorant, which are separated by a gap of some hun- 

 dreds of miles from the geographical race of the same species belonging 

 to Florida and the Carolinas. 



Other birds which come on the scene between Cape Cod and the 

 Bay of Fundy are the great black-backed and herring-gulls. Lams 

 marinus and L. argentatus^ which are now quickly spreading south down 

 the coast, and the arctic tern Sterna paradisaea, which still nests as far 

 south as Cape Cod. If we move north to the Gulf of St. Lawrence, 

 we can also bring in an outpost population of the European cormorant 

 Phalacrocorax carbo, the ring-billed gull Larus delawarensis, which is 

 very closely related to our common gull, the common guillemot 

 Uria aalge, and, rather surprisingly, an arctic species, Briinnich's 

 guillemot Uria lomvia, whose breeding distribution extends from the 

 Magdalen Islands via Newfoundland and Labrador to the High Arctic 

 There is a curious relict population of the Caspian tern also here. 

 In many ways the Gulf of St. Lawrence has arctic properties and 

 there is, as we have seen, a very steep gradient in water temperature 

 at its mouth, at the convergence of the west wind drift and the Labrador 

 current. Here we find the southern outposts of the largest temperate 

 North Atlantic sea-bird, the gannet Sula bassana — though the majority 

 of its breeding-population is found on the other side of the ocean; 

 and we meet our first kitti wakes Rissa tridactyla. 



In structure the coasts of the Atlantic right round from Maine via 

 Nova Scotia, the Gulf of St. Lawrence, Newfoundland, Labrador, 

 Greenland and Iceland to Britain, have a good deal of similarity. 

 They have a fairly even supply of estuaries, inlets, beaches, sands, 

 cliffs, skerries, stacks and islands, and it is probable that the distribu- 

 tion of no sea-bird is seriously limited by lack of suitable nesting sites. 



There are two inland species of North American dark-headed gull, 

 Franklin's gull Larus pipixcan, and Bonaparte's gull L. Philadelphia, 

 neither of which breeds near the coast. 



From the Gulf of St. Lawrence, via Newfoundland, Labrador, 

 Greenland and the Canadian Arctic Archipelago, we find a gradual 

 disappearance of the temperate, sub-arctic and some low arctic species 

 as we progress towards the shores where the sea is still near-freezing 



