glaucoides - kumlieni

(last update: January 26, 2012)

AERC TAC 2003. AERC TAC's taxonomic recommendations.

Online version: www.aerc.eu

Complete 2003 PDF

Page 57:

Thayer’s Gull Larus thayeri suggested to remain as is;
Iceland Gull Larus glaucoides suggested to become monotypic.

Traditionally, Iceland Gull is composed of two subspecies, nominate glaucoides and L. g. kumlieni; following that approach, birds that appear intermediate between Kumlien’s and Thayer’s are called hybrids. Based on historical evidence, however, Weir et al. (2000) suggest that ‘kumlien’s may be best treated as a hybrid swarm between Thayer’s Gull and Iceland Gull. This paper is based on journals and museum documents from historical and more recent expeditions to the Arctic, examination of museum skins and includes about 124 cited references (which see). ‘Three Iceland Gull taxa were defined mainly from adult wingtip melanism. Up until about 1860, nominate glaucoides (no melanism) was known to breed from Greenland to W High Arctic Canada, but by about 1900 it was essentially confined to Greenland. Until 1860, thayeri (most melanism) was known only from W High Arctic Canada, but from 1900 to 1980 it was found throughout High Arctic Canada and a small part of NW Greenland. At high latitudes in Canada it replaced glaucoides, with which it was formerly sympatric in the west and probably interbred. The first known kumlieni (intermediate, variable melanism) were from West Greenland in the 1840s, and by 1900 the western and northern limits of most of its breeding range in the E Canadian Arctic were known. The range of kumlieni lies between those of thayeri and glaucoides and overlaps both: kumlieni bred in Greenland by 1964. It freely interbreeds with thayeri and probably with glaucoides. Winter ranges of glaucoides and thayeri have changed little since they were first determined for glaucoides by 1860 and for thayeri by the 1920s. However, winter adult kumlieni was unknown from Greenland to the British Isles until 1900; there were a few records prior to 1915 and progressively more after 1950. The study adds to the evidence that kumlieni represents introgressive hybridisation by westem thayeri into eastern glaucoides’. Mind, however, that Voous (1977c) recognised L. thayeri and L. glaucoides. Banks & Browning (1999) pointed out a number of questions that need to be addressed regarding the taxonomy of Thayer's Gull. Caution is also needed with the published molecular results (Crochet et al. 2002) based on a single specimen of ‘thayeri’ collected in Louisiana. P.-A. Crochet commented: ‘I had not realised at the time when I requested this specimen (LSUMZ B-21816) that it was out-of-range and of contentious ID. We have now sequenced five more specimens of thayeri from California and the Pacific coast. A short note should appear soon in the Auk to complete our previous paper. None of these specimens group with our previous "thayeri". None groups with glaucoides or kumlieni either... but with glaucescens. Taxonomy of white-winged gulls needs more research.’

ID of Thayer's Gull: Martin Garner and Anthony McGeehan (1998) Identification of juvenile and first-winter Thayer's Gull. Birding World 11(3): p94-101
Useful collection of high quality photographs from British Columbia, Newfoundland, Connecticut and California. Discussion of separation from Glaucous-winged Gull (or hybrids thereof) and American Herring Gull. In this same issue (p86), there is an interesting photo by Bryan Thomas of a first-winter Kumlien's Gull standing alongside a presumed first-winter nominate Iceland Gull taken in the Isles of Scilly.

ID of Thayer's Gull: Howell, S & Elliott, M T. 2001. Identification and variation of winter adult thayer's gulls - with comments on taxonomy. Alula 7 (4): 130-144
(on variation in adult wing-tip pattern with some taxonomic comments)

ID of Kumlien's Gull: Howell, S. N. G., and B. Mactavish. 2003. Identification and variation of winter adult Kumlien's Gulls. Alula 9:2-15.