42 SEA-BIRDS 



time held to be a hybrid between the 'Iceland' gull of Greenland and 

 L. a. thayeri^ Thayer's gull of the Canadian Arctic and Thule corner 

 of north-west Greenland. But there seems no doubt that it is a valid 

 race (Taverner, 1933) with its own discrete breeding-distribution 

 in southern Baffin Island, though on the western marches of its distri- 

 bution there are apparently some forms intermediate between it and 

 thayeri (Horring, 1937) and colonies off south-west Baffin Island have 

 been described as mixed (Soper, 1928). 



The palest of all the herring-gulls is the 'Iceland' gull. Unquestion- 

 ably this extremely pale bird, with pale flesh legs, is a herring-gull, 

 and conspecific with the other herring-gulls of North America. Reports 

 of its breeding in the Canadian arctic archipelago are due to confusion 

 with thayeri; there is no evidence whatever of its overlapping with this 

 or any other subspecies of L. argentatus anywhere; and its similarity 

 in size, structure and plumage is obvious. It is just a very pale kind of 

 herring-gull; and at the same time happens, through convergence, 

 to be extraordinarily similar to, though smaller than, the glaucous 

 gull. * It is entirely confined to Greenland, breeding north to Melville 

 Bay on the west (this inhospitable coast separates it from thayeri) and to 

 Kangerdlugssuaq (at the south end of the Blosseville coast) on the 

 east. Evidence of its breeding farther north in east Greenland, and 

 elsewhere (e.g. Franz Josef Land, Novaya Zemlya) is quite unsatis- 

 factory, and probably due to confusion with the glaucous gull; on 

 Jan Mayen it was stated by F. Fischer to be as abundant as the glaucous 

 gull in 1882-83, and to be nesting on low ledges, but it has not been 

 proved to breed there since. 



In a complex situation, such as this, a confusion of scientific 

 names is to be expected. In other cases it is often found that the 

 vernacular name is less equivocal, and certainly more stable, than the 

 scientific name! Such is not the present case, however; for the name 

 'Iceland gull' makes confusion worse confounded. It has never bred 



*It is an interesting and additionally confusing fact that the "Iceland" gull 

 resembles the larger glaucous gull, L. hyperboreus (with which it overlaps throughout 

 its breeding-range), more than it resembles the neighbouring subspecies of its own 

 species ; and that the western forms of the fuscus group resemble in plumage the 

 larger great blackback L. marinus (with which they overlap geographically) more 

 than do the eastern argentatus herring-gulls (with which they also overlap). The 

 glaucous gull and great blackback are closely related to each other, but are distinct 

 species whose breeding range considerably overlaps; within the overlap hybridiza- 

 tion is not unknown, though extremely rare. Hybridization between herring-gulls 

 and lesser blackbacks in the zone of their overlap is also not unknown, though rare. 

 Hybridization between glaucous gulls and herring-gulls has also been recorded. 



