Splitting headaches? Recent taxonomic changes affecting the British and Western Palearctic lists Martin Collinson ABSTRACT This paper summarises the taxonomic changes that have affected the BOU British List and the British Birds Western Palearctic list since 2000. The purpose of this review is to present these changes simply and clearly, in a single document to provide an easy reference, and to give brief, non-technical explanations of the reasons underlying the decisions. Similar updates will be provided in future in BB on a more regular basis. Introduction http://www.britishbirds.co.uk/bblist.htm), it The editorial policy of British Birds is to follow should be stressed that these decisions relate to taxonomic changes adopted by the British the BOU British and AERC Western Palearctic Ornithologists’ Union Records Committee on lists. the recommendation of its Taxonomic Sub- Some of the changes implemented by the committee (TSC). For Western Palearctic taxa BOU and BB prior to 2000 but subsequent to that are outside the remit of the BOURC, rec- the publication of Voous’s List of Holarctic Birds ommendations of the Taxonomic Advisory in the 1970s are are listed in Appendix 1. Four Committee (TAC) of the Association of Euro- taxonomic changes that are peripheral to the pean Records and Rarities Committees (AERC) British List, but upon which the BOURC TSC are normally followed. Both the BOURC TSC has not yet commented, have been incorporated and the AERC TAC have published several rele- into the present BB Western Palearctic list fol- vant papers since 2000 that alter the taxonomy lowing the recommendations of the AERC TAC. of the British and Western Palearctic lists: Knox These are that the following pairs of taxa are et al. (2002), Sangster et al. (2002a), AERC treated as separate species: Bermuda Petrel (2003), Sangster et al. (2004a) and Sangster et Pterodroma cahow and Black-capped Petrel P. al. (2005). The following summary is in no way hasitata; Oriental Honey-buzzard Pernis intended to replace the properly referenced ptilorhyncus and Honey-buzzard P. apivorus; statements contained in those publications. Amur Falcon Falco amurensis and Red-footed These papers, with the exception of Sangster et Falcon F. vespertinus; and Saunders’s Tern Ster- al. (2002a), are available online at nula saundersi and Little Tern S. albifrons. These http://www.bou.org.uk/recbrlst.html and changes are not discussed further here. One tax- http://www.aerc.eu. Species-level decisions are onomic change that falls outside the remit of the made by the TSC on the basis of the com- BOURC TSC has been adopted by AERC but mittee’s Guidelines (Helbig et al. 2002), which is not included in the BB list. This is the placement also available online at http://www.bou.org.uk/ of Demoiselle Crane Anthropoides virgo in the recbrlst.html. This paper summarises the deci- genus Grus. Phylogenetic studies have not yet sions contained in these papers, for easy refer- fully resolved the relationships between different ence and to act as a source of quick reminders groups of cranes, and there seems little point to the reasoning underlying the changes. making changes until these are better studied. Although the emphasis here is on the British For each decision listed below, the previous Birds Western Palearctic list (available online at English or scientific species name or higher 306 © British Birds 99 • June 2006 • 306–323 Splitting headaches: recent taxonomic changes taxon involved is given first, in bold, with the common ‘white-cheeked’ ancestral species that relevant change(s) summarised in italics, looked like modern-day Canada geese. Barnacle including the original BOURC or AERC refer- Goose and Hawaiian geese diverged greatly in ence for further information. Identification plumage from this ancestor, but Greater and papers and other references are listed in the Lesser Canada Goose much less so. The older lit- normal way, but the TSC and AERC TAC erature reports several parts of the range where reports are abbreviated as follows: TSC1 = Knox large- and small-bodied Canada geese breed et al. (2002); TSC2 = Sangster et al. (2004a); close to each other, but in separate habitats and TSC3 = Sangster et al. (2005); AERC1 = Sang- without hybridisation. Identification in the field ster et al. (2002a); and AERC2 = AERC (2003). remains a problem; the best structural pointer to Finally, the main paragraphs of text summarise Lesser Canada Goose is generally the shorter, the reasoning and flesh out the details of the stubbier bill. Although the race parvipes is collo- recommendation, including, where appropriate, quially known as ‘Lesser Canada Goose’ in the an explanation or literal translation of newly USA and Canada, it is in fact a Greater Canada adopted generic scientific names. Goose B. canadensis parvipes. The American Ornithologists’ Union (AOU) has also adopted Taxonomic changes to the British and this split, but chose ‘Cackling Goose’ as the ver- Western Palearctic lists nacular name for B. hutchinsii, retaining ‘Canada Goose’ for B. canadensis. In fact, over 30 dif- 1. Species-level taxonomy ferent vernacular names have previously been Bewick’s Swan Cygnus columbianus used for Canada geese subspecies, and it is not The two subspecies of Bewick’s Swan continue to possible to retrieve an old name that defines be treated as conspecific (TSC1, AERC2) either species unambiguously. Naming them ‘Big The two subspecies of Bewick’s Swan, C. c. Canada Goose’ and ‘Little Canada Goose’ would columbianus and C. c. bewickii, have been pro- seem to be the next-best alternative! For identifi- posed as potential splits because they differ in cation, see http://www.sibleyguides.com/ the amount of yellow on the bill (summarised canada_cackling.htm, http://www. in Sangster et al. 1997). However, it is not clear oceanwanderers.com/CAGO.Subspecies.html whether there is any overlap, and although and http://www.dfw.state.or.us/ODFWhtml/ hybridisation occurs there is virtually no infor- InfoCntrWild/PDFs/Goose_ID_Book.pdf mation on the relationships between the two taxa in that part of eastern Siberia where they Common Teal Anas crecca come in contact. Green-winged and Eurasian Teal have been split (AERC1) Canada Goose Branta canadensis There are diagnostic plumage differences Greater and Lesser Canada Goose should be between male Green-winged A. carolinensis and treated as separate species (TSC3) Eurasian Teals A. crecca, and limited genetic evi- Both morphology and genetics suggest that the dence suggests that carolinensis is more closely ‘large-bodied’ and ‘small-bodied’ Canada geese related to the morphologically divergent form separate lineages. Genetically, the small- Speckled Teal A. flavirostris than it is to crecca. bodied birds appear to be closer to Barnacle As described in Sangster et al. (2001), they Goose B. leucopsis than they are to the large- should therefore be treated as separate species: bodied taxa, and the large taxa are closer to the Green-winged Teal A. carolinensis (monotypic) Hawaiian goose complex (of which only the Nene and Eurasian Teal A. crecca (polytypic, with B. sandvicensis survives). This is a surprising result subspecies crecca and nimia). The basis for and, if true, ‘Canada Goose’ as we previously recognition of nimia, the larger, Aleutian sub- understood it comprises at least two species: species of Eurasian Teal, is very weak (Sangster Greater Canada Goose B. canadensis (with sub- et al. 2001). species canadensis, fulva, interior, maxima, moffitti, occidentalis and parvipes), and Lesser Canada Greater Scaup Aythya marila Goose B. hutchinsii (with subspecies hutchinsii, The subspecies nearctica has been recognised leucopareia, minima and taverneri). (TSC3) It is assumed that Canada geese, Hawaiian Greater Scaup has been treated as monotypic geese and Barnacle Goose all evolved from a since the 1971 BOU Checklist (BOU 1971) British Birds 99 • June 2006 • 306–323 307 Splitting headaches: recent taxonomic changes without any explanation. However, Pacific and four groupings, which are now classified as four Nearctic birds have a stronger pattern of ver- genera: the North Pacific albatrosses Phoebas- miculation on the mantle and scapulars, and tria, great albatrosses Diomedea, sooty alba- should be recognised as a separate subspecies trosses Phoebetria and ‘mollymawks’ A. m. nearctica. There are no Western Palearctic Thalassarche. Three species of mollymawk have records of nearctica. been recorded in the Western Palearctic: Black- browed Albatross Thalassarche melanophris Scoters Melanitta (formerly Diomedea melanophris), Shy Alba- Black and Common Scoter should be treated as tross T. cauta and Yellow-nosed Albatross T. separate species; White-winged and Velvet Scoter chlororhynchos. The only Diomedea now on the should be treated as separate species (TSC3) Western Palearctic list is Wandering Albatross All six scoter taxa (two ‘black’ scoters, three D. exulans. See Sangster et al. (2002b) for ‘white-winged’ scoters and Surf Scoter M. per- further details. spicillata) are 100% identifiable on the basis of several clear differences in shape, structure and Mediterranean Shearwater colour of their bills, which males use as signals Puffinus mauretanicus during courtship display. Common M. nigra Balearic and Yelkouan Shearwaters have been and Black Scoters M. americana also differ split (AERC1) clearly in vocalisations, as do Velvet M. fusca Formerly regarded as the western and eastern and White-winged Scoters M. deglandi.There subspecies (mauretanicus and yelkouan respec- are small plumage differences between Velvet tively) of ‘Mediterranean Shearwater’, Balearic and White-winged Scoters too. Together, these and Yelkouan Shearwaters are genetically diver- differences, which are likely to affect mate gent (about 3% difference in mtDNA choice, are clear enough to warrant specific sequences), have skeletal and obvious plumage recognition for: differences (Balearic being a heavier bird with Common Scoter M. nigra (monotypic) darker underparts), and differ in their migration Black Scoter M. americana (monotypic) strategies. They do not share colonies but their Velvet Scoter M. fusca (monotypic) breeding ranges are separated only by a short White-winged Scoter M.