PROC. BIOL. SOC. WASH. 99(1), 1986, pp. 149-159 SUBSPECIES OF THE GLAUCOUS GULL, LARUS HYPERBOREUS (AVES: CHARADRIIFORMES) Richard C. Banks Abstract. —Current writings treat the Holarctic Glaucous Gull, Larus hyper-boreus, either as a monotypic species or as having two or three subspecies; if divided, birds of Canada, Greenland, and Europe are considered to be of the nominate subspecies. This study shows that there are four subspecies, the birds of Canada and Greenland being separable from those of Europe; the name L. h. leuceretes Schleep, 1819, based on a Greenland bird, is available for the former. Alaskan birds {L. h. barrovianus) are relatively dark on the mantle, those of Canada and Greenland are pale, those of Europe and western Asia are dark, and those of Siberia {pallidissimus) are very pale. From the small Alaskan birds there is an increase in size to the east around the Holarctic to very large birds in Siberia. The Alaskan and Canadian populations intergrade in extreme northwestern Canada. Nonbreeding Glaucous Gulls along the Pacific coast of North America are of the Alaskan form, barrovianus; those east of the Rockies, previously referred to as barrovianus or hyperboreus, are all leuceretes or, in the western plains states, from the intergrade area. The nature and extent of geographic vari-ation in the Holarctic Glaucous Gull, Larus hyperboreus, and the nomenclatural recog-nition of this variation have been a matter of dissent since the species was first divided in the late 1 9th century. Authorities writing in the last two decades have considered the species to be either monotypic or composed of two or three subspecifically distinct pop-ulations. Authors who recognize subspecies have not agreed on the application of names or on the boundaries of the named popu-lations. A request for subspecific identification of a wintering specimen prompted a reexam-ination of the series of this species in the National Museum of Natural History (USNM), the American Museum of Natural History (AMNH), and the Academy of Nat-ural Sciences of Philadelphia (ANSP), and some individual specimens borrowed from other institutions (see Acknowledgments), as well as the taxonomic literature of the species. This has allowed the identification of some of the sources of earlier disagree-ment, and revealed that geographic varia-tion is more complex than has been rec-ognized. I believe that four populations are recognizable at the subspecific level. Taxonomic History The name Larus glaucus Briinnich, 1 764, was used for the Glaucous Gull until the early part of the 20th century. The Ameri-can Ornithologists' Union (A.O.U. 1908), citing a manuscript by C. W. Richmond (ap-parently never published), noted that Larus glaucus of Briinnich is preoccupied by Lar-us glaucus Pontippidan, 1763, a synonym of Larus canus Linnaeus, 1758, and that the next available name is Larus hyperboreus Gunnerus, 1767. The latter has been the accepted specific name ever since. Ridgway (1886) described Larus barro-vianus as an Alaskan species of gull that was smaller and darker than the related North Atlantic L. glaucus. The name barrovianus was applied to Bering Sea birds by Tacza-
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