Swans to Ducks

Brent Goose Branta bernicla

Three subspecies are 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. This latter subspecies was removed from the list of BBRC taxa in 2006.

However, a fourth Brent Goose population, breeding mainly on Melville and Prince Patrick Islands in western High Arctic Canada, has also been described, 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) and Reeber (2015) also 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 or with other ‘northwestern’ geese. 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 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 welcomes claims of this form though the committee is unable to progress submissions for the time being, pending clarification of its taxonomic position. However, even if this can be clarified, details of a ringed or marked bird might be necessary for formal acceptance. (updated Dec 2017 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.

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.

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

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

 

Canada Goose Branta canadensis

The following subspecies 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 of Canada Goose and Cackling Goose, the former 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 such 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 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 a particular 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 ‘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 nominate canadensis will require definitive evidence of a North American origin. (updated Dec 2017 AMS).

References

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

 

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 nominate 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 here.

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 nominate 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 Dec 2017 AMS).

References

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

 

Taiga Bean Goose Anser fabalis

Taiga Bean Geese of the nominate Scandinavian and north-west Russian subspecies are regular winterers in Britain. To the east two other subspecies are recognised – the west Siberian johanseni (‘Johansen’s Bean Goose’) and the east Siberian middendorffii (‘Middendorff’s Bean Goose’).

Neither johanseni nor middendorffii is on the British List though both appear to be potential vagrants.

Identification of an extralimital Taiga 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. The subspecies middendorffii is biometrically distinct.

Field notes and photographs of potential vagrant subspecies are welcomed but the minimum requirements for acceptance are likely to be biometric data (middendorffii) or details from a ringed or marked bird. Acceptance to a johanseni/middendorffii subspecies pair might be possible. (updated Dec 2017 AMS).

References

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

 

Tundra Bean Goose Anser serrirostris

Tundra Bean Geese of the north-west Russian subspecies rossicus are regular winterers in Britain. To the east nominate serrirostris (‘Thick-billed Bean Goose’) breeds across Siberia.

The subspecies serrirostris is not on the British List but appears to be a potential vagrant.

Identification of serrirostris 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. Biometrics are distinct.

Field notes and photographs of serrirostris are welcomed but the minimum requirements for acceptance are likely to be biometric data or details from a ringed or marked bird. (updated Dec 2017 AMS).

References

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

 

White-fronted Goose Anser albifrons

Five subspecies are recognised – albifrons (‘Eurasian White-fronted Goose’) breeding in northern Russia, flavirostris (‘Greenland White-fronted Goose’) breeding in west Greenland, gambelli breeding in Alaska, north-west and north central Canada, elgasi (‘Tule White-fronted Goose’) breeding in southern Alaska and sponsa breeding in western Alaska. The taxonomy of White-fronted Geese is widely debated, however. For an overview of recent taxonomic proposals relating to White-fronted Geese see Mooij and Zöckler (2000), Banks (2011), Reeber (2015) and http://www.sibleyguides.com/2011/03/distribution-of-greater-white-fronted-goose-subspecies/.

The subspecies albifrons and flavirostris both winter in Britain but no other subspecies is on the British List. Of the remaining subspecies, elgasi and sponsa are perhaps unlikely vagrants. However, gambelli is a more likely vagrant and has already been suspected here (Millington 2008).

The identification of gambelli or any vagrant subspecies is likely to be problematic. 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 Dec 2017 AMS).

References

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

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.

Distribution of Greater White-fronted Goose subspecies

 

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 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 Dec 2017 AMS).

 

Eider Somateria mollissima

Six subspecies are recognised – mollissima (north-west Europe), faeroeensis (Faeroes and potentially southern Iceland and Shetland (Furness et al. 2010)), borealis (north-east Canada, Greenland and Iceland), sedentaria (Hudson Bay), dresseri (north-east North America) and v-nigrum (north-west Canada, Alaska and north-east Siberia).

Only the subspecies mollissima 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 subsequent claims of borealis have been considered by BBRC but none were considered acceptable and all have been published as ‘not proven’. The subspecies sedentaria is reported to be largely resident in Hudson Bay but dresseri and v-nigrum are potential vagrants to Britain. A dresseri was in Ireland in January 2010 (Farrelly & Charles 2010) and (subject to acceptance) a v-nigrum was recorded in northern Norway in February 2014 (http://birdingfrontiers.com/2014/02/19/pacific-eider-in-norway-a-new-western-palearctic-bird/).

The field identification of dresseri and v-nigrum is potentially straightforward, at least with adult or near-adult males. 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. Biometrics may also assist with confirming identification. However, given the clinal nature of variation in north-east Atlantic populations, the identification of faeroeensis and borealis is more problematic (Garner et al. 2008, Garner & Millington 2010 and Hellquist 2014).

The Committee welcomes claims of dresseri and v-nigrum but claims of faeroeensis and borealis are only sought if accompanied by a ringing recovery. (updated Dec 2017 AMS).

References

British Ornithologists’ Union. 2006. 7th Checklist. Ibis 148: 526-563.

British Ornithologists’ Union. 2008. 37th Report. Ibis 151: 224-230.

British Ornithologists’ Union. 2010. 39th Report. Ibis 153: 231.

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.

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