Abstract When considering additions to the British List, wildfowl are among the most controversial group of bird species for the British Ornithologists’ Union Records Committee (BOURC) to consider. Their field identification is often straightforward but determining their provenance as either wild or of captive origin can be problematic. Falcated Duck Mareca falcata is no exception, with the assessment of this species’ position on the British List having lasted for more than 30 years. A bird at Welney, Norfolk, in 1986, and subsequently in Northamptonshire, has now been added to Category A of the British List, although opinion both within and outside the Committee remains divided. This paper provides an account of BOURC’s treatment of this challenging file.
Distribution
Falcated Duck breeds mainly in eastern Russia, in southern Siberia, Transbaikal, Amurland and Ussuriland. Its range extends west to the Angara River basin and the upper reaches of the River Yenisey, north to the headwaters of the Lena and Yana rivers, and east to Kamchatka, southern Sakhalin and the Kuril Islands. Outside Russia it also nests in Hokkaido (Japan) and south to northern Mongolia and northeast China (Delacour 1954; Cramp & Simmons 1977; Melnikov 2000; Reeber 2015). It favours water meadows and lakes in lowland valleys but it is nowhere common. The most recent surveys, in 2002–07, estimated a global population of 89,000 individuals, but the species is thought to be in decline (Cao et al. 2008; Reeber 2015) and it is currently classified by BirdLife International as ‘Near Threatened’ (BirdLife International 2019).
The species migrates south to winter in northeast India, south and east China, North and South Korea and central and southern Japan. It also occurs in winter in small numbers in Bangladesh, northern Laos, Myanmar, Nepal, Taiwan, Thailand and Vietnam. In winter it frequents lowland rivers, lakes, flooded meadows and, less frequently, coastal lagoons and estuaries, mixing with other ducks, particularly Eurasian Wigeons M. penelope and Pintails Anas acuta (BirdLife International 2019).
A potential vagrant to Britain?
Falcated Duck is a long-distance migrant with a breeding range, wintering range and migration routes overlapping with those of many other East Asian bird species observed as vagrants in western Europe. For example, it has a more southerly breeding range than Baikal Teal Sibirionetta formosa, but winters farther south and west.
There is an established track record of vagrancy for Falcated Duck, with observations from the west of the Indian Subcontinent (Gujarat, India; Sind, Pakistan), Central Asia, the Middle East, Europe and North America. In the central Palearctic region, vagrants have been noted in Kazakhstan, Afghanistan, Iraq, Jordan, Oman and Turkey (Cramp & Simmons 1977). The species has also wandered east into the western Pacific, to the Philippines (Carboneras & Kirwan 2019) and the Mariana Islands (Howell et al. 2014).
There are also records in a number of European countries, including Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Hungary, Malta, the Netherlands, Poland, Portugal, Spain, Sweden and Switzerland. Here, however, the situation is obscured by the occurrence of escapes from collections, and the species is treated differently from country to country. Some (e.g. the Netherlands) recognise the occurrence of wild birds and have added the species to their national list; some (e.g. Belgium and Spain) retain the species in Category D; and others (e.g. Germany and Switzerland) regard all records as relating to escapes, and have assigned the species to Category E. However, Berlijn (2007) noted that almost all European records involve birds in the period from October to June, with late spring/early summer observations concentrated in more northerly countries. This apparent pattern of movement across Europe argues that a proportion of these birds might be of wild origin, and is one of the reasons why the species was accepted to Category A in the Netherlands.
In the northern Pacific, birds have reached the Pribilof and west and central Aleutian Islands, and the continental west coast of North America, from Alaska south to California. There are also records farther east, in central North America – in Ontario (Canada), and Ohio, Maryland, North Carolina and Virginia (USA) – but these are generally assumed to relate to escapes (Berlijn 2007; Howell et al. 2014).
Almost all records of apparent or potential vagrants in both the Palearctic and the Nearctic have involved males, although females were recorded in Jordan in 1969 and Switzerland in 1996 (Berlijn 2007). It seems likely that, being less distinctive than males, some females are being overlooked.
Transatlantic vagrancy to Britain by Nearctic wildfowl has been long recognised and has been confirmed by recoveries of birds ringed in North America. Among the ‘dabbling ducks’ these include a Green-winged Teal A. carolinensis, two Blue-winged Teals Spatula discors and two American Wigeons M. americana (Hudson 1973; Votier et al. 2003; Forrester et al. 2007). The mechanisms of such vagrancy are relatively clear, presumably involving birds displaced eastward into the Atlantic while on autumn migration or as a result of winter hard-weather movements, and subsequently carried to Europe on the prevailing westerly airflow. As a result, records of other North American duck species which have not been substantiated by a ringing recovery – such as Redhead Aythya americana, Canvasback A. valisineria, Bufflehead Bucephala albeola and Hooded Merganser Lophodytes cucullatus – have also been admitted to Category A of the British List where the circumstantial evidence suggested that a wild bird was most likely involved in a similar displacement event.
Vagrancy by East Asian wildfowl has, by contrast, suffered from something of a ‘credibility gap’. With a predominantly overland route, the mechanisms for such long-distance displacement are very different. Although these mechanisms are not fully understood, the role of ‘carrier species’ with which an individual may abmigrate is likely to be important. In the case of Falcated Duck, the key potential carrier species is the Eurasian Wigeon (hereafter ‘Wigeon’).
Wigeons breed throughout the northern Palearctic, from western Europe to eastern Siberia. The breeding range therefore overlaps extensively with that of the Falcated Duck. Many Wigeons winter in eastern Asia, but birds from as far east as the River Yenisey in central Siberia regularly winter in western Europe, including in Britain (Cramp & Simmons 1977). Evidence for such movements is provided by ringing recoveries. Seven Wigeon recoveries from between 80º and 90º east, mainly between the Kanin Peninsula and the Rivers Ob and Irtysh, are cited by Owen & Mitchell (1988), and the species has also yielded multiple recoveries along the River Yenisey (Wernham et al. 2002).
Wigeons wintering in Britain have been recovered farther east too. One bird ringed ‘on the western part of the Wash’ on 28th January 1974 was recovered near Khatanga, north-central Siberia (102º E) on 9th June 1976. This location lies as far east as the breeding range of Falcated Duck (although farther to the north). Another Dutch-ringed Wigeon has been recovered even farther into Siberia, at Irkutsk (108º E), well within the breeding range of Falcated Duck. There is clearly potential for a Falcated Duck to abmigrate and find itself in the company of westbound migrating Wigeons.
Further confidence in the ability of East Asian wildfowl to reach western Europe naturally has recently been provided by stable-isotope evidence from a Baikal Teal. The analysis of a first-calendar-year bird shot near Skælskør, Sjælland, Denmark, on 24th November 2005 showed different values for feathers grown on the breeding grounds compared with those grown on or near the wintering grounds (Fox et al. 2007). The natal-area values were consistent with a continental Siberian origin while those from the wintering area were consistent with coastal western Europe. Although stable-isotope data are not as conclusive as a ringing recovery, this does nevertheless suggest that the bird originated within the breeding range of Baikal Teal and that its occurrence in Denmark was the result of natural vagrancy.
A similar analysis, with near-identical results, was subsequently undertaken on a second-calendar-year Baikal Teal shot at Tillingham, near Maldon in Essex, on 1st January 1906 (Votier et al. 2009). This suggested that the Danish record was not unique and confirmed that Baikal Teal can reach western Europe. Supported by this evidence, a first-calendar-year male at Minsmere, Suffolk, on 18th November to 29th December 2001 was admitted to Category A of the British List (Harrop & McGowan 2009). Since then, a further six records have been accepted by BBRC as involving apparently wild individuals.
Falcated Ducks in captivity
Delacour (1954) noted that although the first specimen record for Europe dates back to before 1785, the Falcated Duck remained very scarce in collections for a long time. Many were imported from China after 1908, however, and captive breeding then became regular. The captive stock was almost wiped out during the Second World War but was replenished, and is thought to be currently stable. The species is now widely kept and bred, both in Britain and elsewhere in Europe, for example 60 were bred in Germany in 1986 (Kleefisch 1989).
It is, however, still not common in captivity. Falcated Ducks cost £7.00 each in 1975, rising to £35.00 by 1991 (T. P. Inskipp in litt.), with Reeber (2015) noting that, of the Holarctic duck species, it is ‘usually the most expensive, along with Baikal Teal’. At the time of writing, the ‘Zootierliste’ database of public and private collections (www.zootierliste.de/en) lists Falcated Duck under ‘current holdings’ as present in five collections in the UK (with nine collections listed under ‘former holdings’). Elsewhere in Europe it is listed as being present in 35 collections in 11 countries (and formerly in 54 collections in 15 countries). Around 212 are thought to have been in captivity in Britain in 1990 with 178 by 2001 (the comparable figures for Baikal Teal are 160 and 377). The species is also less common in captivity than both Bufflehead and Hooded Merganser (A. Harrop in litt.). Nevertheless, proven or strongly suspected escapes occur ‘rather frequently’ in Europe (Berlijn 2007).
British records
There are few historical records of Falcated Duck in Britain but an increase took place from the 1970s onwards. The following is not an exhaustive list but represents the records received and published by BBRC and subsequently considered by BOURC.
1. Leicestershire, male, Cropston Reservoir, 27th December 1975 to 27th March 1976 (Brit. Birds 87: 567; Ibis 122: 568, 133: 220, 135: 497).
2. Warwickshire, male, Kingsbury Water Park, 24th October to 6th December 1981 (Brit. Birds 87: 567; Ibis 133: 220, 135: 497).
3. Yorkshire, male, Potteric Carr, 4th–7th February 1984 (Brit. Birds 87: 567; Ibis 135: 497).
4. Nottinghamshire, male, Retford, 26th January 1985, possibly since 13th (Brit. Birds 89: 529).
5. Norfolk, male, Welney, 9th–10th and 27th December 1986, presumed same 20th August to 8th October 1987 (Brit. Birds 87: 567; Ibis 133: 220, 135: 497).
6. Kent, male, Motney Hill, 6th February to 17th March 1987, presumed same Lower Rainham, 26th and 31st May 1987 (Ibis 133: 220, 135: 497).
7. Northamptonshire, male, Pitsford Reservoir, 15th February to 5th April 1987, same Thrapston and Ringstead GP, 12th December 1987 to 6th March 1988 (all presumed same as Welney, Norfolk) (Brit. Birds 87: 567; Ibis 133: 220, 135: 497).
8. Cambridgeshire, male, Buckden, 1st April 1988 (Brit. Birds 87: 567; Ibis 133: 220, 135: 497).
9. Norfolk, male, Cley, 7th–15th May 1988, presumed same 11th–28th May 1989 (Brit. Birds 87: 567).
10. Warwickshire, male, Middleton, 5th November 1989 (Brit. Birds 87: 567).
11. Devon, male, Kenwith, 19th October to 6th December 1991 (Brit. Birds 87: 567).
12. Essex, male, Old Hall Marshes, 16th January to 11th April 1994 (Brit. Birds 88: 555).
13. Yorkshire, male, Blacktoft Sands, 22nd May 1994 (Brit. Birds 91: 515).
14. Lincolnshire, male, Kirkby-on-Bain, 19th–21st February 1995 (Brit. Birds 89: 529).
15. Clyde, male, Merryton Haugh, 8th–15th March 1998 and 1st November 1998 to 24th May 1999 (Brit. Birds 92: 607).
16. Hertfordshire, male, Wilstone Reservoir, 13th–20th January 1999 (Brit. Birds 100: 751–752).
17. Orkney, male (shot), Shapinsay, 24th November 2000, specimen at National Museums Scotland, Edinburgh, accession number NMS.Z 2002.86 (Brit. Birds 94: 501; Ibis 153: 230, 154: 214; Forrester et al. 2007) (plate 18).
18. Suffolk, male, Minsmere, 14th May to 10th June 2002 (Brit. Birds 97: 623).
19. Kent, male, West Hythe and Lympe, 15th April to 14th June 2003 (Brit. Birds 107: 650).
20. Devon, first-/second-calendar-year male, Exe Estuary, 18th November 2006 to 11th January 2007, same (adult male), Countess Wear Sewage Works, 30th January to 4th May 2008 (Brit. Birds 100: 751–752, 101: 575, 102: 598–599; plates 019 & 20).
21. Staffordshire, male, Copmere, 26th November 2007 to at least 5th April 2008 (Brit. Birds 102: 599).
22. Anglesey, male, Llyn Traffwll, 17th–29th May 2008 (Brit. Birds 102: 598–599).
23. Kent, male, Broadditch Pond, Southfleet, 18th January 2008 to at least June 2009 (Brit. Birds 102: 598–599).
24. Oxfordshire, adult male, Farmoor Reservoir, 9th–13th December 2012 (Brit. Birds 106: 637–638).
25. Hampshire, adult male, Bury Marsh, 9th February 2013 (Brit. Birds 109: 627).
BOURC assessment
The assessment history of Falcated Duck has been both long and tortuous. Identification has rarely been a problem, however. Adult males are highly distinctive, and the only real pitfall involves hybrids. Hybrid pairings with Wigeon, Gadwall M. strepera, Garganey S. querquedula, Mallard Anas platyrhynchos, Common Shelduck Tadorna tadorna and Ruddy Shelduck T. ferruginea have been noted in the wild (Berlijn 2007; Reeber 2015), and other hybrid combinations have arisen among captive birds. First-/second-calendar-year male Falcated Ducks show less pronounced plumage characters but should still attract attention. However, females and eclipse males are much more subdued in their appearance and many if not most may escape detection.
The problem has instead always been one of determining whether any given record involves a bird of ‘apparently natural’ origin, and so warranting a claim on Category A of the British List, or an escape from captivity, and so being placed instead in Category E. At least one of the records listed above (Copmere, Staffordshire, 2007/08) involved a likely escape, and was published as such by BBRC. Others, however, were potentially wild birds.
The BOURC 10th Report (BOU 1984) stated that the 1975/76 Leicestershire record was considered ‘almost certainly to have been an escape from captivity’. In the 19th Report (BOU 1993) all the eight records considered were placed in Category D1, ‘where there is a reasonable doubt that they have ever occurred in the wild state’, with the comment that natural origin could not be excluded, but seemed unlikely.
The species then remained in Category D, although it has, in line with BOURC procedures, been subject to periodic review. This review process was, however, deferred for long periods pending two lines of investigation: the stable-isotope analysis of the Orkney bird in 2000 and the clarification of the age on arrival of the 2006–08 Devon bird.
With regard to the Orkney bird, it was shown to have a deuterium signature inconsistent with two sampled individuals from the natural range in the eastern Palearctic. This means that it grew the feathers sampled either in a different place from the two ‘within-range’ specimens or in the same place during a year with very different rainfall patterns. The results were considered inconclusive and did not provide evidence in support of natural vagrancy (Forrester et al. 2007).
As for the Devon bird in 2006–08, its age on arrival provoked considerable debate. Initially, it was thought to be a first-/second-calendar-year when it first arrived (Langman 2006) but was later considered to be an adult in eclipse plumage (Fraser et al. 2007). However, doubts about this diagnosis emerged (Hudson et al. 2008), and further research showed that the bird was in fact a first-/second-calendar-year after all (Martin & Garner 2012). The fact that it was an immature was considered by some to boost its credentials as a genuine vagrant, since many extralimital birds are immatures, with inexperience in migration explaining their vagrancy.
With these two investigations complete, the file was recirculated. Changing Committee membership inevitably brings new perspectives and there was now an increasing acceptance that Falcated Duck could occur in Britain in a natural state. The vagrancy potential of the species had previously been considered unlikely by some, but most voters now regarded it as likely, a view bolstered significantly by the admission of Baikal Teal to the British List in 2009.
The key issue became the level of proof required to accept an individual as occurring in an ‘apparently natural’ state, and so qualify for Category A. In the absence of definitive proof of origin, the Committee’s task was to come to the best judgement possible based on the available evidence. There were in effect two options:
1) accept only a ringed bird originating from the natural range, or a bird with convincing stable-isotope analysis; or
2) accept a bird with the fullest possible credentials for a natural origin, without the need for ringing or isotope evidence.
Among the Committee there was a majority preference for the second of these options, an approach consistent with that taken for Nearctic wildfowl accepted to the British List.
The next round of voting was completed in 2015 (BOU 2016). Of the 11 votes cast, seven were for Category A (with five votes for the 2006/08 Devon bird as the ‘first’) and four for Category D. This failed to achieve the two-thirds majority required for placement in either Category A or D, and so the file was recirculated.
The subsequent round of voting in 2016 was as follows. Of the eight votes cast (by this time there were fewer voting members), seven were for Category A (for the 2006–08 Devon bird) and one for Category D. However, this round of voting did not include all relevant records and a further recirculation of a complete file was undertaken.
This round of voting was completed in 2017, with the results as follows. Of the eight votes, six were for Category A (with four votes for the 2006/08 Devon bird) and two for Category D. Although a majority for Category A was still evident, there was still no agreement on which individual would qualify as the ‘first’. It was agreed to revisit the file and assess each record against a number of criteria; and that a candidate for Category A should:
- • be fully-winged
- • be definitely unringed (unless involving a ringed bird from the natural range)
- • behave as a wild bird
- • be with an appropriate carrier species (essentially this means Wigeon)
- • be at a location frequented by wild ducks (note, however, that Falcated Ducks in the Eastern Palearctic can, in addition to natural sites, associate with other ducks on urban park lakes; Hudson et al. 2013; pers. obs.)
- • arrive at an appropriate time of year for a vagrant, and not linger through the summer
If it was a first-calendar-year bird, this would be supportive, but the age was not seen as critical, since many adult vagrant wildfowl, including returning birds, have been observed.
In this context, a number of records appeared to be promising candidates but failed against the full list of criteria, often due to the absence of a definitive statement about whether the bird was ringed. Although possibly involving wild birds, they could not be put forward as potential ‘firsts’.
Five individuals were considered to meet all the criteria. The earliest dated of these was the adult male at Welney, Norfolk, on 9th–27th December 1986, then Pitsford Reservoir, Northamptonshire, from 15th February to 5th April 1987, Welney again from 20th August to 8th October 1987, and finally at Thrapston and Ringstead Gravel-pits, Northamptonshire, from 12th December 1987 to 6th March 1988.
This bird was fully winged, seen clearly to be unringed, behaved as a wild bird, accompanied Wigeons, and arrived in early winter at a site attracting high numbers of wintering wildfowl. Its early return date in August 1987 was flagged as a potential concern, being too early for a bird which had summered in eastern Siberia; but it may have migrated to northern Europe or western Russia with Wigeon and returned early as a failed breeder.
A final round of voting in early 2019 resulted in six votes for Category A (five for the Welney bird and one for ‘2006/08 Devon or Welney’) and two for Category D. The Welney bird was therefore admitted to Category A of the British List and the formal announcement was made in February 2019 (www.bou.org.uk/british-list/changes-1-feb-2019).
The assessment of the post-1986 records, to determine which may be also considered wild, now falls to BBRC, and this process will begin in 2020.
Acknowledgments
We thank members of BBRC and BOURC for their consideration of the British records summarised here. We also thank Bob McGowan (National Museums Scotland) for information about the Orkney specimen, and for the photographs in plate 18. The British List is sponsored by Leica, and the authors acknowledge their continued support of the BOU and the work of the BOURC.
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Andy Stoddart, BBRC Vice-Chairman, 7 Elsden Close, Holt, Norfolk NR25 6JW; e-mail [email protected]
Christopher J. McInerny, BOURC Secretary, School of Life Sciences, University of Glasgow, Glasgow G12 8QQ; e-mail [email protected]
