Swans to Ducks

Bewick’s Swan Cygnus columbianus

The Siberian-breeding subspecies bewickii is a regular winter visitor to Britain. The North American subspecies columbianus (‘Whistling Swan’) is on Category A of the British List, with two accepted individuals.

This latter subspecies has an all-black bill with just a small yellow spot in front of the eye. However, columbianus is reported to have bred with bewickii in Siberia, so birds with apparently intermediate bill patterns may be attributable to such events or may also represent the extreme of variation within bewickii. Birds with mud on the bill, reducing the apparent amount of yellow, are a further potential source of confusion.

Field notes, preferably accompanied by photographs, should constitute acceptable evidence of columbianus but only birds with bills matching the classic pattern are likely to be accepted. Descriptions should also indicate how an escaped Trumpeter Swan C. buccinator was excluded. Biometric data or details from a ringed or marked bird would of course provide additional confirmation. (updated June 2014 AMS).

References

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Oxford University Press, Oxford.

 

Bean Goose Anser fabalis

Bean Geese of the Scandinavian and northwest Russian taiga-breeding subspecies fabalis (‘Taiga Bean Goose’) and the northwest Russian tundra-breeding subspecies rossicus (‘Tundra Bean Goose’) are regular winterers in Britain. To the east the traditional taxonomy (e.g. Cramp et al. 1977) recognises three other subspecies – the west Siberian taiga-breeding johanseni (‘Johansen’s Bean Goose’), the east Siberian taiga-breeding middendorffii (‘Middendorff’s Bean Goose’) and the Siberian tundra-breeding serrirostris (‘Thick-billed Bean Goose’). The taxonomy of the Bean Geese is not settled, however. Sangster & Oreel (1996) and AOU (2007) adopted a two-way split into a taiga-breeding species and a tundra-breeding species, the former authority regarding each as monotypic, the latter recognising each as comprising two subspecies (johanseni being synonymised with fabalis). Most recently, Ruokonen et al. (2008) proposed a different arrangment based on DNA analysis – ‘Bean Goose’, comprising fabalis, rossicus and serrirostris, and ‘Middendorff’s Goose’ A. middendorffii (monotypic). None of the extralimital subspecies is on the British List though all appear to be potential vagrants.

Identification of an extralimital Bean Goose is likely to be problematic. Observers should pay particular attention to overall size and structure, neck length, head structure, bill size and structure (both from the side and above), bill pattern and tail pattern. Both middendorffii and serrirostris are biometrically distinct.

Field notes and photographs of potential vagrant subspecies are welcomed but the minimum requirement for acceptance is likely to be biometric data (middendorffii and serrirostris) or details from a ringed or marked bird. Acceptance to a johanseni/middendorffii subspecies pair might be possible. (updated Sept 2015 AMS).

References

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Oxford University Press, Oxford.

Ruokonen, M., Litvin, K. & Aarvak, T. 2008. Taxonomy of the bean goose – pink-footed goose. Molecular Phylogenetics and Evolution 48: 554-562.

Sangster, G. & Oreel, G. J. 1996. Trends in systematics; Progress in taxonomy of Taiga and Tundra Bean Geese. Dutch Birding 18: 310-316.

 

White-fronted Goose Anser albifrons

Traditional taxonomy (e.g. Cramp et al. 1977) recognises five subspecies: albifrons (‘Eurasian White-fronted Goose’) breeding in west Siberia, flavirostris (‘Greenland White-fronted Goose’) breeding in Greenland, frontalis breeding in East Asia and North America, gambelli breeding in the Mackenzie Basin, Canada and elgasi (‘Tule White-fronted Goose’) breeding in southern Alaska. East Asian birds are sometimes treated as albicans. Species status has been proposed for flavirostris (Fox & Stroud 2002). The taxonomy of White-fronted Geese is widely debated, however. For an overview of recent proposals see Mooij and Zöckler (2000), Banks (2011), Reeber (2015) and http://www.sibleyguides.com/2011/03/distribution-of-greater-white-fronted-goose-subspecies/. These authors regard East Asian birds as belonging to albifrons, assign most North American birds of both taiga and tundra-breeding forms to gambelli, do not recognise frontalis and assign two populations of west and south-west Alaskan breeders to sponsa.

The subspecies albifrons and flavirostris both winter in Britain but no other subspecies is on the British List. Of the remaining traditionally recognised subspecies, elgasi is considered an unlikely vagrant. However, frontalis and gambelli are potential vagrants and both have already been suspected here (Millington 2008).

Identification of either is likely to be problematic, however. Nevertheless, observers should pay particular attention to overall size and structure, neck length, bill size and shape, eye-ring, plumage hues, upperparts patterning, belly barring, tail pattern and habitat preference.

Field notes and photographs of potential vagrants are welcomed but the minimum requirement for acceptance is likely to be details from a ringed or marked bird (though biometrics might also prove useful). (updated Nov 2015 AMS).

References

Banks, R. C. 2011. Taxonomy of the Greater White-fronted Geese (Aves: Anatidae). Proc. Biol. Soc. Wash. 124; 226-233.

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Oxford University Press, Oxford.

Fox, A. D. & Stroud, D. A. 2002.The Greenland White-fronted Goose Anser albifrons flavirostris.BWP Update 4: 6588.

Millington, R. G. 2008. “White-fronted Geese of four kinds” in Garner et al. 2008. Frontiers in Birding, Birdguides, Sheffield.

Mooij, J. H. & Zöckler, C. 2000. Reflections on the systematics, distribution and status of Anser albifrons. Casarca 6: 92-107.

Reeber, S. 2015. Wildfowl of Europe, Asia and North America. Helm, London.

http://www.sibleyguides.com/2011/03/distribution-of-greater-white-fronted-goose-subspecies/

 

Greylag Goose Anser anser

The nominate subspecies occurs in Britain as a native breeder, an introduced, naturalised breeder, a winter visitor from Iceland and a wanderer from the continent (from both wild and feral populations). The subspecies rubrirostris (‘Eastern Greylag Goose’) occurs across Asia but is said to intergrade with anser across eastern Europe and western Russia and it has also been introduced to the near-continent (Cramp et al. 1977). The subspecies rubrirostris is not on the British List but birds resembling this form have occurred in Britain.

Identification of rubrirostris is likely to be problematic but observers should pay particular attention to overall size, plumage hues, upperparts fringes and bill colour. Pink-billed birds can sometimes be found amongst flocks of naturalised anser but these often lack the full suite of rubrirostris characters and are likely to be intergrades. However, some intergrades presumably resemble true rubrirostris more closely and it is not clear how the latter might then be distinguished.

Field notes and photographs of potential vagrant rubrirostris are welcomed but the minimum requirement for acceptance is likely to be biometric data or details from a ringed or marked bird from east of the Urals or the Black Sea. (updated June 2014 AMS).

References

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Oxford University Press, Oxford.

 

Canada Goose Branta canadensis

Following the split of the Canada Geese by AOU in 2004 (and subsequently by BOURC) into Canada Goose and Cackling Goose, the following subspecies of the former are recognised: nominate canadensis (‘Atlantic Canada Goose’), interior (‘Todd’s Canada Goose’), parvipes (‘Lesser Canada Goose’),  fulva (‘Vancouver Canada Goose’), maxima (‘Giant Canada Goose’), moffitti (‘Moffitt’s Canada Goose’) and occidentalis (‘Dusky Canada Goose’).

In the wake of the split, Canada Goose was re-categorised from Category A to Category C of the British List (the latter in respect of the introduced, naturalised population comprising mainly the subspecies canadensis). A record of two birds in Aberdeenshire in 1992/93, one of which was marked with a neck-collar (and shot), was then accepted by BOURC as the first vagrant occurrence for Britain, enabling the species to be re-admitted to Category A. Further individuals have now been accepted by BBRC. The neck-collared bird resembled the Hudson Bay-breeding subspecies interior (and came from Maryland, within the core wintering range of that form) but it appears on the British List as ‘probably interior’ and is accepted by BBRC as ‘interior/parvipes’. Subsequent individuals have also been accepted as ‘interior/parvipes. The subspecies interior is on paper the most likely vagrant form to reach Britain though, despite a westerly breeding range, birds resembling the west Canadian-breeding parvipes have also been noted. The east Canadian-breeding nominate canadensis also appears to be a potential vagrant.   

Identification of Canada Geese to subspecies (and even sometimes to species) can be problematic. Observers should pay particular attention to the overall size of the bird, preferably in direct comparison with other geese, neck length, head shape, bill size and shape, plumage hues and any dark ‘gular stripe’ or white neck ‘collar’. There are, however, few definitive criteria for identifying any of the subspecies whilst particular uncertainties surround the ‘intermediate-sized’ parvipes and the similar taverneri Cackling Goose.

BBRC welcomes submissions of all (post-1950) Canada Geese considered to be vagrants and for which contemporaneous evidence is available. Such birds will be assessed firstly as relating to the subspecies pair interior/parvipes but will also be considered to subspecies level where sufficient evidence exists to do so. Any firm racial attributions will be sent to BOURC for consideration for admission to the British List. Also sought are records of birds of which cannot readily be assigned to either Canada or Cackling Goose. Any such birds accepted will be published as ‘either/or’. In terms of evidence, acceptance to the subspecies pair interior/parvipes should be possible based on field notes, preferably accompanied by photographs. Photographs alone can be misleading, but prolonged observation will ‘average out’ potentially misleading impressions. Biometric data or details from a ringed or marked bird would of course provide additional confirmation and are likely to be necessary for acceptance to subspecies.

In terms of origin, the ideal evidence will be a ringing recovery or details of a marked bird. However, BBRC will consider any birds showing evidence of a wild origin, e.g. those accompanying potential Arctic goose ‘carrier species’ (Icelandic Greylag Geese, Greenland White-fronted Geese, Pink-footed Geese or Barnacle Geese) and/or on dates and in locations consistent with vagrancy. Establishing provenance is of course, as with all wildfowl, an inexact science but submissions of lone birds, birds with feral geese and birds on dates or in locations less indicative of vagrancy will be less likely to gain acceptance. Any claim of a vagrant of the nominate subspecies canadensis will require definitive evidence of a North American origin.

This policy is perhaps best viewed as a ‘holding position’. In reality, much remains to be discovered about all the ‘Canada Geese’, and further taxonomic change seems inevitable. Of particular relevance is the work of Hanson (2006, 2007) who proposed at least six species and over two hundred subspecies. Following collaboration with Hanson, Anderson (2010) went on to propose fifteen species and 181 subspecies. Whilst these treatments have provoked much debate, they nevertheless provide an alternative, more ‘fine-grained’ approach which may yet prove useful in understanding the origin and identity of birds reaching Britain. Potential vagrants should therefore be documented as fully as possible so that records can, if necessary, be reviewed in the light of any future taxonomic readjustments. (updated Sept 2015 AMS).

References

Anderson, B.W. 2010. Evolution and taxonomy of White-cheeked Geese. AVVAR Books, California.

Batty, C. & Lowe, T. 2001. Vagrant Canada Geese in Britain and Ireland. Birding World 14: 57-61.

Batty, C., Hackett, P. & Lowe, T. 2001. Vagrant Canada Geese in Britain: Autumn 2001. Birding World 14: 515-519.

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Oxford University Press, Oxford.

Garner, M. 2008. “White-cheeked Geese – Canada Goose and Arctic Goose: a new approach to their taxonomy and identification” in Garner et al. 2008. Frontiers in Birding. Birdguides. Sheffield.

Hanson, H.C. 2006 & 2007. The White-cheeked Geese: taxonomy, ecophysiographic relationships, biogeography and evolutionary considerations. Vol 1 & Vol 2. AVVAR Books, California.

 

Cackling Goose Branta hutchinsii

Following the split of the Canada Geese the smaller species was initially named ‘Lesser Canada Goose’ by BOURC but as the same name applies to parvipes Canada Goose, ‘Cackling Goose’ has been widely accepted as more appropriate. The following subspecies of Cackling Goose are recognised: hutchinsii (‘Richardson’s Cackling Goose’), minima (‘Ridgway’s Cackling Goose’), taverneri (‘Taverner’s Cackling Goose’) and leucopareia (‘Aleutian Cackling Goose’).

Cackling Goose is not on the British List though a number of records have been accepted by BBRC and submitted to BOURC for consideration for admission to Category A.  The Canadian High Arctic-breeding subspecies hutchinsii is the most likely and apparently the most common vagrant form, though the north and west Alaskan-breeding taverneri and even the west Alaskan-breeding minima are also candidates. BOURC is also considering whether any of the submitted records enables the admission of hutchinsii to the British List.

Identification of Cackling Geese to subspecies (and even sometimes to species) can be problematic (see Mlodinow et al. (2008) for a full exploration of the problems). Observers should pay particular attention to the overall size of the bird, preferably in direct comparison with other geese, neck length, head shape, bill size and shape, plumage hues, upperparts pattern and any dark ‘gular stripe’ or white neck ‘collar’. There are, howeve, few definitive criteria for identifying any of the subspecies whilst particular uncertainties surround the ‘intermediate-sized’ taverrneri and the similar parvipes Canada Goose.

On current knowledge, this species warrants continuing treatment as a ‘BB rarity’. BBRC therefore continues to seek submissions of all (post-1950) Cackling Geese considered to be vagrants and for which contemporaneous evidence is available. Such birds will be assessed firstly as ‘Cackling Geese’ but will also be considered to subspecies level where sufficient evidence exists to do so.  Any future firm racial attributions will be sent to BOURC for consideration for admission to the British List. Also sought are records of birds which cannot readily be assigned to either Canada or Cackling Goose. Any such birds accepted will be published as ‘either/or’.

In terms of identification (both to species and subspecies), good field notes, preferably accompanied by photographs, should constitute acceptable evidence. Photographs alone can be misleading, but prolonged observation will ‘average out’ potentially misleading impressions. DNA evidence, biometric data or details from a ringed or marked bird would of course provide additional confirmation.

In terms of origin, the ideal evidence will be a ringing recovery, details of a marked bird or even stable isotope analysis. However, BBRC will consider any birds showing evidence of a wild origin, e.g. those accompanying potential Arctic goose ‘carrier species’ (Icelandic Greylag Geese, Greenland White-fronted Geese, Pink-footed Geese or Barnacle Geese) on dates and in locations consistent with vagrancy. Establishing provenance is of course, as with all wildfowl, an inexact science but the relatively high number of minima and low number of hutchinsii in captivity is noted. Submissions of lone birds, birds with feral geese and birds on dates or in locations less indicative of vagrancy will be unlikely to gain acceptance.

This policy is perhaps best viewed as a ‘holding position’. In reality, much remains to be discovered about all the Canada Geese and further taxonomic change seems inevitable. Of particular relevance is the work of Hanson (2006, 2007) who proposed at least six species and over two hundred subspecies. Following collaboration with Hanson, Anderson (2010) went on to propose fifteen species and 181 subspecies. Whilst these treatments have provoked much debate, they nevertheless provide an alternative, more ‘fine-grained’ approach which may yet prove useful in understanding the origin and identity of birds reaching Britain. Potential vagrants should therefore be documented as fully as possible so that records can, if necessary, be reviewed in the light of any future taxonomic readjustments.

References

Anderson, B.W. 2010. Evolution and taxonomy of White-cheeked Geese. AVVAR Books, California.

Batty, C. & Lowe, T. 2001. Vagrant Canada Geese in Britain and Ireland. Birding World 14: 57-61.

Batty, C., Hackett, P. & Lowe, T. 2001. Vagrant Canada Geese in Britain: Autumn 2001. Birding World 14: 515-519.

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Oxford University Press, Oxford.

Garner, M. 2008. “White-cheeked Geese – Canada Goose and Arctic Goose: a new approach to their taxonomy and identification” in Garner et al. 2008. Frontiers in Birding. Birdguides. Sheffield.

Hanson, H.C. 2006 & 2007. The White-cheeked Geese: taxonomy, ecophysiographic relationships, biogeography and evolutionary considerations. Vol 1 & Vol 2. AVVAR Books, California.

Mlodinow et al. 2008. Distribution and Identification of Cackling Goose (Branta hutchinsii) Subspecies. North American Birds 62: 344-360.

 

Brent Goose Branta bernicla

Three subspecies are normally recognised. The Siberian-breeding bernicla (‘Dark-bellied Brent Goose’) and the Svalbard, Franz Josef Land, Greenland and Arctic Canadian-breeding hrota (‘Pale-bellied Brent Goose’) are regular winterers in Britain whilst the Arctic Canadian, Alaskan and east Siberian-breeding nigricans (‘Black Brant’) is a scarce winter visitor from both ends of the range which was removed from the list of BBRC species in 2006. Some authors (e.g. Shields 1990) regard the Brent Geese as specifically distinct.

However, a fourth Brent Goose population, breeding mainly on Melville and Prince Patrick Islands in western High Arctic Canada, has also been recognised, though its taxonomic status remains uncertain and it has no scientific name. It is generally known as ‘Grey-bellied Brant’ or ‘Western High-Arctic Brant’. Its appearance is stated to be highly variable, though combining features of both hrota and nigricans (leading to speculation that it might be an intergrade form), but it has been proposed as a valid taxon on the basis of preliminary DNA analysis as well as morphology (Shields 1990). Lewis et al. (2013) recognised it as a distinct subspecies, noting further that the original nigricans type specimen resembles a ‘Grey-bellied Brant’. If this is the case then, under nomenclatural rules, ‘Grey-bellied Brant’ becomes nigricans, with ‘Black Brant’ adopting the already available name orientalis.

‘Grey-bellied Brant’ is not on the British List (an inevitable situation given its uncertain taxonomic status) but a number of birds apparently of this type have occurred in Ireland (Garner & Millington 2001) and several have been suspected in Britain (e.g. Hutt & Taylor 2006). Several claims have been received by BBRC and are currently held on file. Given that its breeding range abuts that of Arctic Canadian hrota, it is clearly a potential vagrant to Britain and is most likely to occur with birds from that population. Other suspected ‘Grey-bellied Brants’ have reached the eastern United States but their identity remains under discussion (Buckley & Mitra 2002).

Observers of any putative ‘Grey-bellied Brant’ should pay particular attention to the upperpart tone, size of neck ‘collar’, neck/body contrast and precise underparts and flank pattern. However, the morphological limits of this form are not yet fully defined. Some birds may be so close in appearance to hrota or nigricans as to be indistinguishable from the extremes of variation in these subspecies (themselves not fully known) whilst other actual or hypothetical Brent Goose intergrade combinations might also resemble birds from this population. Intergradation between bernicla and nigricans and between bernicla and hrota has been noted (albeit rarely) so it seems likely that nigricans and hrota may intergrade also. 

BBRC would welcome further submissions of putative individuals of this form though the committee is unable to progress claims for the time being pending recognition of the status of ‘Grey-bellied Brant’ by BOURC. However, if the taxonomic position can be clarified, details of a ringed or marked bird would probably be necessary for acceptance. (updated Sept 2015 AMS).

References

Buckley, P. A. & Mitra, S. S. 2002. Three geese resembling “Gray-bellied Brant”/ “Lawrence’s Brant” from Long Island, New York. North American Birds 56: 502-507.

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Oxford University Press, Oxford.

Garner, M. & Millington, R. G. Grey-bellied Brant and the Dundrum conundrum. Birding World 14: 151-155.

Garner, M. 2008. Brent Geese of four kinds: Dark-bellied Brent, Pale-bellied Brent, Black Brant and Grey-bellied Brant in Garner et al. 2008. Frontiers in Birding. Birdguides. Sheffield.

Hutt, A. & Taylor, G. 2006. The apparent Grey-bellied Brant in East Yorkshire. Birding World 19: 113-117.

Lewis, T.L., Ward, D. H., Sedlinger, J.S., Reed, A. & Derksen, D .V.  2013. BNA Online.

Shields, G. F. 1990. Analysis of mitochondrial DNA of Pacific Black Brant. Auk 107: 620–623.

 

Common Eider Somateria mollissima

Traditional taxonomy recognises six subspecies of Eider – mollissima (north-west Europe), faeroeensis (Faeroes – and potentially southern Iceland and Shetland (Furness et al. 2010)), borealis (arctic North Atlantic), sedentaria (Hudson Bay), dresseri (north-east North America) and v-nigrum (north-west Canada, Alaska and north-east Siberia). The wider taxonomy of the north Atlantic populations remains controversial, however, with some authors including faeroeensis within mollissima. Livezey (1995), proposed a rearrangement of the Eiders into four species – ‘European Eider’ (S.mollissima), ‘Northern Eider’ (S.borealis), ‘Dresser’s Eider’ (S.dresseri including sedentaria) and ‘Pacific Eider’ (S. v-nigrum). Most recently, however, the 11th BOU TSC Report contains the following: “Our review of evidence for geographic variation in the three subspecies borealis, faeroeensis and mollissima indicates that no clear subdivisions have been documented, that variation is mostly clinal, and that recognition of multiple subspecies is problematic. Thus, all Western Palearctic populations are treated as a single subspecies, S. m. mollissima” (BOU 2015). The subspecies ‘faeroeensis’ and ‘borealis’ are therefore now regarded as invalid.

The subspecies mollissima (as now defined) is on the British List. A former Category D record of ‘borealis’ (a tideline corpse in Lothian in 1978) was inadvertently admitted to Category A (BOURC 2006) but was later removed on the grounds that the biometrics were inconclusive and that the bill colour suggested intergradation (BOURC 2008, 2010). A number of claims of ‘borealis‘ have previously been considered by BBRC but none were considered acceptable and all have been published as ‘Not proven’. The subspecies sedentaria is said to be largely resident in Hudson Bay but dresseri and v-nigrum are potential vagrants to Britain. dresseri was in Ireland in January 2010 (Farrelly & Charles 2010) and a v-nigrum was recorded in northern Norway in February 2014 (subject to acceptance by the Norwegian rarities committee). 

The field identification of dresseri and v-nigrum is potentially straightforward, at least with adult or near-adult males. Nevertheless observers should pay close attention to the forehead, crown and bill shape, the colour of the bill-base, the size and shape of the frontal lobes, the position of the nostril in relation to the facial feathering, the shape of the facial feathering, the shape of the black line between the bill and the facial feathering, the shape of the lower border of the black cap, the extent of green on the sides of the head, the presence or absence of a black ‘v’ on the throat, the presence or absence of scapular ‘sails’ and the colour of the legs and feet. Where possible, size measurements taken in the hand may assist with confirming identification.

The Committee welcomes claims of dresseri and v-nigrum but claims of ‘borealis’ are no longer sought. (updated Jan 2016 AMS).

References

BOU. 2015. Taxonomic recommendations for Western Palearctic birds: 11th report. Ibis

BOURC. 2006. 7th Checklist. Ibis 148: 526-563.

BOURC. 2008. 37th Report. Ibis 151: 224-230.

BOURC. 2010. 39th Report. Ibis 153: 231.

Cramp, S. et al. 1977. The Birds of the Western Palearctic. Vol. 1. Oxford University Press, Oxford.

Farrelly, W. & Charles, D. 2010. The Dresser’s Eider in County Donegal – a new Western Palearctic bird. Birding World 23: 62-64.

Furness, R.W., Mable, B., Savory, F., Griffiths, K., Baillie, S.R. & Heubeck, M. 2010. Subspecies status of Common Eiders Somateria mollissima in Shetland based on morphology and DNA. Bird Study 57: 330-335.

Garner et al. 2008. Frontiers in Birding. Birdguides, Sheffield.

Garner, M. & Millington, R. 2010. The forms of Common Eider: their identification, taxonomy and vagrancy. Birding World 23: 65-82.

Hellquist, A. 2014. Identification of Northern Eider. Dutch Birding 36: 221-231.

Kehoe, C. 2006. Racial identification and assessment in Britain. Brit. Birds 99: 619-645.

Livezey, B.C. 1995. Phylogeny and evolutionary ecology of modern seaducks (Anatidae: mergini). Condor 97: 233-255.

http://birdingfrontiers.com/2014/02/19/pacific-eider-in-norway-a-new-western-palearctic-bird/