speciesaccounts_whooperswanWhooper Swan

Cygnus cygnus

The Iceland population of Whooper Swan breeds exclusively in Iceland and winters primarily in Britain and Ireland, with smaller numbers remaining in Iceland and some also migrating as far as the near European continent.

There are four other populations of Whooper Swan: i) the Northwest European population breeds in Scandinavia and north European Russia and winters in northwest and central Mainland Europe; ii) the Black Sea and east Mediterranean population breeds in northern Europe and western Siberia and winters in the Black Sea and east Mediterranean; iii) the Caspian and central Asia population breeds in west and central Siberia and winters in the Caspian and central Asia; and iv) the east Asia population breeds in central and east Siberia to northeast China and winters in east Asia.

Whooper Swans undertake what is probably the longest sea crossing of any swan species, migrating 800-1,400 km between Britain/Ireland and Iceland.

The Goose & Swan Monitoring Programme only monitors the Iceland population of Whooper Swan.

  • Conservation Status

    Global status (IUCN Red List of Threatened Species)

    African-Eurasian Waterbird Agreement (AEWA)

    European status (European Red List of Birds)

    The Birds Directive (European Commission)

    UK status (Birds of Conservation Concern)

    UK quarry species (Wildlife & Countryside Act 1981)

    Least Concern

    A3c*

    Least Concern (Europe and EU27)

    Annex I

    Amber

    not huntable

    Population Status

    Flyway population size (CSR 6; Wetlands International 2015)

    GB estimate (Musgrove et al. 2011)

    Irish estimate (Crowe & Holt 2013)

    GB trend (SUKB 2016)

    Breeding success (GSMP survey)

    29,000 – 29,300 individuals

    11,000 individuals

    14,530 individuals

    Long-term trend (1988/89 – 2013/14): 98% increase
    Ten-year trend (2003/04 – 2013/14): 51% increase

    Varies markedly between years and sites, generally 10 – 20%

    Summary statistics

    Census-derived estimates of the population size of Iceland Whooper Swan, 1986-2015; recorded during the International Swan Census.

    Census year Estimate of population size
    2015 34,004
    2010 29,3001
    2005 26,366
    2000 20,856
    1995 15,842
    1991 18,035
    1986 16,742

    1Since the publication of January 2010 census results (Hall et al. 2012), additional counts totalling 68 birds were received from four sites in the Republic of Ireland resulting in a revised 2010 population estimate of 29,300 (previously 29,232).

    Annual estimates of the percentage of young (%) and mean brood size (young per successful pair) of Whooper Swan in Britain (recorded at WWT Caerlaverlock, WWT Martin Mere & Ribble Estuary, and the Ouse Washes, where data are collected annually), 2003/04-2015/16.

    Season Percentage of young (%) Mean brood size
    2015/16 11.8 1.9
    2014/15 16.0 2.0
    2013/14 13.3 1.9
    2012/13 13.0 1.9
    2011/12 10.6 1.9
    2010/11 14.4 2.1
    2009/10 13.0 1.9
    2008/09 14.9 2.1
    2007/08 20.4 2.6
    2006/07 13.8 2.5
    2005/06 10.6 2.4
    2004/05 13.7 2.4
    2003/04 15.0 2.4

     

    References

    Crowe, O. & C. Holt. 2013. Estimates of waterbird numbers wintering in Ireland, 2006/07-2010/11. Irish Birds 9: 545-552

    Musgrove, A.J., G.E. Austin, R.D. Hearn, C.A. Holt, D.A. Stroud & S.R. Wotton. 2011. Overwinter population estimates of British waterbirds. British Birds 104: 364-397.

  • Iceland Whooper Swans breed throughout Iceland (Garðarsson & Skarphedinsson 1984). Large flocks of non-breeders and failed breeders gather on marine and brackish waters in Iceland during late summer, and the majority leave Iceland from mid October to mid November; ringing and count programmes indicate that most migrate to winter in Britain and Ireland, with a small proportion remaining to overwinter in Iceland (Black & Rees 1984, Gardarsson 1991, Rees et al. 2002). Sites in northern Britain and Ireland act as major landfalls, e.g. Shetland, Orkney and, especially, Loughs Swilly and Foyle in Northern Ireland (Robinson et al. 2004).

    flyway map whooper

    Flyway of Iceland Whooper Swan

    Spring migration back to Iceland starts in March and April. Satellite tacking studies have shown that the swans may fly either direct from Ireland to Iceland, a 1,400 km flight overseas, or via Scotland (Rees 2009), though there is a minimum 800 km flight between Britain and Iceland and the birds are susceptible to strong head or side winds blowing them off course (Pennycuick et al. 1996, Rees 2009).

    In Ireland, Whooper Swans are distributed throughout, with highest numbers usually found at Loughs Neagh & Beg (Antrim, Armagh, Down, Londonderry, Tyrone), Lough Foyle (Donegal, Londonderry) and Upper Lough Erne (Fermanagh).

    Two key sites in England regularly hold the majority of wintering Whooper Swans in Britain: WWT Martin Mere & surrounding area (Lancashire) and Ouse Washes (Cambridgeshire, Norfolk). In Scotland, birds are widely distributed; from Orkney down the north and western coast, across to the Outer Herbrides, and down through eastern and central counties to the Solway Estuary in the southwest – this latter site usually holding the highest numbers. Swans are sparsely distributed elsewhere in England and Wales.

    Although the Iceland population is protected throughout its range, illegal shooting remains a threat, with 13% of live Whooper Swans x-rayed since 2000 found with shotgun pellets embedded in their body tissue (Newth et al. 2011). Shooting has also accounted for the death of 8.3% of dead Whooper Swans recovered along their migration route since the 1980s (Newth et al. 2011). Illegal shooting is known to have occurred in all countries within the species range, including the UK (Rees et al. 2002, Newth et al. 2011).

    There is evidence of some interchanges between the Iceland and Northwest European populations. Ring sightings of British ringed birds in Norway, Denmark and the Netherlands suggest that up to 600 birds from the Iceland population may winter in mainland Europe while a small number of Finnish ringed birds have been sighted in Britain giving rise to the suggestion that around 200 birds from the Northwest Europe population visit Britain (Garðarsson 1991, Cranswick et al. 1997, Laubek et al. 1998).

    References

    Cranswick, P.A., J.M. Bowler, S. Delany, Ó. Einarsson, A. Garðarsson, J.G. McElwaine, E.C. Rees & J.H. Wells. 1997. Whooper Swans wintering in Britain, Ireland and Iceland: International Census, January 1995. Wildfowl 47: 17-30.

    Garðarsson, A. 1991. Movements of Whooper Swans Cygnus cygnus neckbanded in Iceland. In: Sears, J. & P.J. Bacon (eds.). Proceedings of the 3rd IWRB International Swan Symposium, Oxford, 1989. Wildfowl Special Supplement No. 1: 189-194.

    Gardarsson, A. & K.H. Skarphedinsson. 1984. A census of the Icelandic Whooper Swan population. Wildfowl 35: 37–47.

    Laubek, B., H.L. Knudsen & A. Ohtonen. 1998. Migration and winter range of Whooper Swans Cygnus cygnus breeding in different regions of Finland. In: Laubek, B. 1998. The Northwest European Whooper Swan (Cygnus cygnus) population: ecological and management aspects of an expanding waterfowl population. PhD thesis, University of Aarhus, Denmark.

    Newth, J.L., M.J. Brown & E.C. Rees. 2011. Incidence of embedded shotgun pellets in Bewick’s swans Cygnus columbianus bewickii and whooper swans Cygnus cygnus wintering in the UK. Biological Conservation 144: 1630-1637.

    Pennycuick, C.J., Ó. Einarsson, T.A.M. Bradbury & M. Owen. 1996. Migrating Whooper Swans Cygnus cygnus: satellite tracks and flight performance calculations. Journal of Avian Biology 27: 118–134.

    Rees, E.C. 2009. Lough Neagh Wetlands Whooper Swan Study: Project Report. WWT Report to Irish Whooper Swan Study Group, Wildfowl & Wetlands Trust, Slimbridge, UK.

    Rees, E.C., K. Colhoun, Ó. Einarsson, J.G. McElwaine, A. Petersen & S. Thorstensen. 2002. Whooper Swan Cygnus cygnus. In: Wernham, C.V., M.P. Toms, J.H. Marchant, J.A. Clark, G.M. Siriwardena & S.R. Baillie (eds.) The Migration Atlas: Movements of the Birds of Britain and Ireland. pp. 154–157. T. & A.D. Poyser, London, UK.

  • International Swan Census

    A coordinated, international census of the Iceland Whooper Swan population is undertaken in Britain, Ireland and Iceland every five years. The census covers many non-wetland and/or temporarily flooded areas that are not routinely covered by other annual schemes.

    Results from the censuses are presented in various reports and papers. See our Reports & newsletter page.

    Find out more about the International Swan Census

    Wetland Bird Survey and Irish Wetland Bird Survey

    Whooper Swan numbers in the UK and Republic of Ireland are monitored annually through the Wetland Bird Survey (WeBS) and the Irish Wetland Bird Survey (I-WeBS), respectively. Although these schemes provide good coverage of a high proportion of wintering sites used by Whooper Swans, a number of non-wetland or temporally flooded areas are not surveyed, hence a more comprehensive census, that focuses specifically on Whooper Swans, is required to fully access the size of the population; such a survey is undertaken every five years (see above).

    GSMP age assessments

    The annual breeding success of the Iceland population of Whooper Swan is monitored in Britain through age assessments that are undertaken throughout the autumn and early winter. Counters record the number of first winter birds present within a flock and individual brood sizes (i.e. how many young in each family group).

    Results from these age assessments are presented on the ‘Latest results’ tab, and a summary table can also be found on the ‘Status summary’ tab.

    Find out more about age assessments

  • Results for 2015/16 [added August 2016]

    Abundance

    WeBS/I-WeBS

    The abundance of Whooper Swan in the UK and the Republic of Ireland in 2015/16 was monitored through the Wetland Bird Survey (WeBS) and the Irish Wetland Bird Survey (I-WeBS), respectively. Results from these schemes are presented in reports which are available via the schemes’ websites.

    International Swan Census

    The seventh international census of the Icelandic Whooper Swan population took place in January 2015. The census was organised overall by the Wetlands International / IUCN SSC Swan Specialist Group, and coordinated in Britain, Ireland and Iceland by WWT in partnership with BirdWatch Ireland and colleagues in Iceland.

    The 2015 census yielded the highest population estimate to date, with a total of 34,004 birds recorded, representing a 16% increase on the 2010 census (Figure 1). All countries, with the exception of Northern Ireland, saw an increase in wintering numbers. England and the Republic of Ireland held an equal proportion of the population (35% recorded in both countries), whilst 11% was recorded in Scotland,  10% in Northern Ireland, 7% in Iceland and less than 1% in Wales and the Isle of Man.

    Figure_WS_1_2016

    Figure 1: The number of Icelandic Whooper Swans recorded during the International Swan Census, 1986–2015. Note: Wales and the Isle of Man are combined as each holds less than 1% of the total population.

    Breeding success

    Whooper Swan age assessments were conducted in six regions across Britain and Ireland during winter 2015/16 (Table 1). Age assessments were made in all regions in mid-winter (between 15 and 19 January 2016 in Britain and between 11 and 22 January 2016 in Ireland), when the majority of families were likely to have arrived from Iceland to wintering sites. Regional variation in the percentage of young and mean brood size was assessed to determine any bias in the geographical distribution of family parties.

    A total of 9,458 Whooper Swans was aged (approx. 28% of the total population; Hall et al. in prep.): 5,743 birds in England, 337 in Scotland, 1,941 in Northern Ireland and 1,437 in the Republic of Ireland (Table 1). Overall, 13.2 % of birds were cygnets and the mean brood size for pairs with young was 2.0 cygnets.

    Table 1. The proportion of young (%) and mean brood size of Whooper Swans during the 2015/16 winter (regions defined below).

    Region Total aged (number of young) Percentage of young (%) Number of broods (number of young) Mean brood size
    Northwest England  1,746 (266)  15.2  147 (266)  1.8
    East Central England  3,997 (403)  10.01  204 (403)  2.0
    Southwest Scotland  231 (30)  13.0  13 (30)  2.3
    West Scotland  106 (19)  17.9  11 (19)  1.7
    Northern Ireland  1,941 (253)  13.0  124 (241)  1.9
    Republic of Ireland  1,437 (280)  19.5  130 (277)  2.1
    Overall  9,458 (1,251) 13.2  629 (1,236) 2.20

    Regions (counties from which data were received in 2015/16):

    • Northwest England: Lancashire (WWT Martin Mere/Ribble Estuary)
    • East central England: Cambridgeshire and Norfolk (WWT Welney/Ouse Washes/Nene Washes), Lincolnshire
    • Southwest Scotland: Dumfries & Galloway
    • West Scotland: Argyll and Bute
    • Northern Ireland: Co. Antrim, Co. Armagh, Co. Down, Co. Fermanagh, Co. Londonderry, Co. Tyrone
    • Republic of Ireland: Co. Cork, Co. Donegal, Co. Galway, Co. Leitrim, Co. Mayo, Co. Meath, Co. Roscommon, Co. Sligo, Co. Waterford, Co. Wicklow

    There was evidence of variation in the distribution of families between regions (X25 =91.7, P < 0.05). Highest breeding success was among birds that wintered in the Republic of Ireland (19.5%) and west Scotland (17.9 %) (Table 1). Lowest breeding success was found for birds wintering in east central England (10.1 %).

    Overall, higher breeding success was found in northern regions (west and southwest Scotland, north west England and Northern Ireland) compared to southern regions (east central England and the Republic of Ireland) (14.1% and 12.6%, respectively; X21 = 4.8, P < 0.05), which may reflect a general preference for Whooper Swan families to select wintering sites closest to their Icelandic breeding grounds (Rees et al. 1997). Regional variation in brood size was also evident, ranging from 1.7 cygnets per family in west Scotland to 2.3 cygnets per family in southwest Scotland.

    The mean percentage of young in flocks at and around WWT centres (i.e. WWT Martin Mere/Ribble Estuary, WWT Welney/Ouse Washes/Nene Washes and WWT Caerlaverock), where data are collected annually, was 11.8% (n =5,873), which was lower than the previous five and ten-year means (2005/06–2014/15; 14.1% ± 0.5 SE and 14.4 % ± 0.3 SE, respectively) (Figure 2; Figure 3). The mean brood size for these three regions was 1.9 cygnets per family, which also fell below the five and ten-year means (2005/06–2014/15; 2.0 ± 0.04 SE and 2.2 ± 0.1, respectively) (Figure 2).

    Figure_WS_2_2_2016Figure 2: The percentage of young  (blue circles), with the rolling five-year mean of % young (red line), and mean brood size (green triangles) of Whooper Swans recorded at WWT Welney/Ouse Washes/Nene Washes, WWT Caerlaverock and WWT Martin Mere/Ribble Estuary, 1997/98–2015/16. Five-year mean values for the percentage of young were calculated for the five years preceding the year in question.

    Figure_WS_3_2_2016

    Figure 3: The percentage of young Whooper Swans recorded at WWT Welney/Ouse Washes/Nene Washes, WWT Caerlaverock, WWT Martin Mere/Ribble Estuary, Northern Ireland and the Republic of Ireland, 1997/98–2015/16.

    Discussion

    In 2015, breeding success for Icelandic Whooper Swans was below average. The proportion of young wintering at and around WWT centres (11.8 %) was lower than the average recorded at these sites over the previous ten years (14.4%). Iceland experienced a very cold spring with some areas remaining snow covered in mid-May, causing unseasonal mortality of some species of wader (K. Brides, pers comm.). Temperatures averaged 9˚C across the country in June (Accuweather 2016) which was below the average daily maximum temperature recorded for this month between 1979 and 2012 (12˚C; Weatherspark 2016). Such unfavourable conditions would have almost certainly impacted on the swans’ breeding success.

    Results from the 2015 international census clearly show a continued increase in the Icelandic Whooper Swan population. Whilst Britain has seen a gradual increase in the proportion of the population it supports, Ireland has seen a continued decline. In 2015, Britain, for the first time since the 1986 census, held a larger proportion of the population than Ireland, albeit by just a small percentage. This increase in Britain is due to a higher rate of increase in England than in the population as a whole, whereas in Northern Ireland and the Republic of Ireland the rate of increase has fallen. This suggests that either some birds may be shifting their winter distribution to England from other parts of the winter range, or that swans in the eastern part of the range are experiencing significantly different levels of breeding success and/or survival than those further west.

    Although Iceland has seen an increase in the number of wintering Whooper Swans, there has only been a small increase in the proportion of the population remaining there to overwinter.  Hence, at present, there is little evidence to suggest a northwards shift in the overall winter distribution, whereby more birds are choosing to remain closer to their breeding grounds in Iceland; which has been seen in other wildfowl species, such as Bewick’s Swan, which are tending to winter closer to their Arctic breeding grounds with the milder winters of the early 2000s (Worden et al. 2006). In fact, the results from recent censuses are suggesting a southerly shift in Whooper Swan distribution, with England holding an increasing proportion of the population.

    The full results of the census will be published in Wildfowl 66.

    Acknowledgements

    Special thanks to all observers and Local Organisers who took part in the international census and the productivity surveys, including the WeBS, I-WeBS, Irish Whooper Swan Study Group and GSMP networks. We are especially grateful to Helen Boland and Graham McElwaine for coordinating the surveys across Ireland.

    References

    Accuweather [Accessed June 2016]:

    Hall, C., Glanville, J.R., Boland, H., Einarsson, O., McElwaine, G., Holt, C.A., Spray, C.J. & Rees, E.C. 2012. Population size and breeding success of Icelandic Whooper Swans Cygnus cygnus: results of the 2010 international census. Wildfowl 62: 73-96.

    Rees, E.C., J.S. Kirby & A. Gilburn. 1997. Site selection by swans wintering in Britain; the importance of habitat and geographic location. Ibis 139: 337-352.

    Worden , J., P.A. Cranswick, O. Crowe, G. McElwaine & E.C. Rees. 2006. Numbers and distribution of Bewick’s Swan Cygnus columbianus bewickii wintering in Britian and Ireland: results of the international censuses, January 1995, 2000 and 2005. Wildfowl 56: 3–22.

    Weatherspark [Accessed June 2016]:

  • Previous annual results will be archived here. Published results from the International Swan Census can be found on the Reports & newsletter page.

    2014/15 Results

    2013/14 Results

    2012/13 Results

    2011/12 Results

    2010/11 Results

    2009/10 Results

    2008/09 Results

    2007/08 Results

    2006/07 Results

    2005/06 Results

  • Background

    Regular colour-marking of Whooper Swans in Britain started in 1980, following the construction of swan-pipes at WWT Caerlaverock and WWT Welney. A swan-pipe is a long, netted trap which is baited with food to encourage birds to enter. A gate is dropped to close off the entrance and the birds are moved into a holding area, before being caught, ringed and released.

    Catches at WWT Caerlaverock have resulted in X Whooper Swans being ringed, and a third swan-pipe at WWT Martin Mere, constructed in 1990, has also led to the capture and ringing of several hundred birds. During the 1980s, the number of Whooper Swans wintering at WWT Welney was relatively low (100-300 birds), and by the winter of 1994/95, when over a thousand birds were first recorded at the site, the swan-pipe had fallen into disrepair, with fewer than 50 swans having been caught (Rees et al. 2002). In 2007, a new swan-pipe was built at the centre and since then over 200 birds have been captured and ringed.

    Whooper Swans have also been caught using cannon-nets in the fields around WWT Welney, although this tends to result in fewer birds being captured but has resulted in x birds ringed.

    Smaller numbers of Whooper Swans have been colour-ringed elsewhere in Britain, including South Uist in the late 1980s, northeast England throughout the 1990s, southwest Wales in 1991 and in Northern Ireland, particularly at Castle Espie, since winter 1992/93 (Rees et al. 2002) and more recently small numbers have been caught by cannon netting in north Wales and north Yorkshire.

    In Iceland, the Whooper Swan ringing programme, using metal rings, started in the 1960s. In the early- to mid- 1980s, a few hundred birds from moulting flocks were marked with neck-collars by Arnthor Gardarsson (Rees et al. 2002). In 1988, WWT in collaboration with Icelandic colleagues caught and colour-ringed Whooper Swans on their breeding territories (Rees & Bowler 1996), and since then annual trips have been made to Skagafjörður, Mývatnsheiði and Jökuldalsheiði in northern Iceland to ring breeding and non-breeding birds. Since 2009, this work has solely been undertaken by Ólafur Einarsson and Sverrir Thorstensen in conjunction with the Icelandic Institute of Natural History.

    Resightings of colour-marked Whooper Swans have lead to a number of important discoveries including:

    • Confirmation that swans move frequently between Britain and Ireland during the winter. Northern parts of Ireland, in particular, are used as staging sites by birds wintering in Britain, as well as those wintering elsewhere in Ireland (McElwaine et al. 1995).
    • Evidence that birds breeding in the more western parts of Iceland (in Skagafjörður) concentrate largely in more western parts of the wintering range (Ireland), whereas those ringed in east Iceland (Norður-Múlasýsla) were more likely to occur in Scotland and in continental Europe (Gardarsson 1991, McElwaine et al. 1995, Newth et al. 2007).
    • Indications of an overall southerly shift in distribution as the winter progressed (McElwaine et al. 1995, Newth et al. 2007).

    WWT’s colour-ringing

    Whooper Swans are caught and ringed at WWT Caerlaverock (Dumfries & Galloway), WWT Martin Mere (Lancashire) and WWT Welney (Norfolk). This is undertaken as part of WWT’s long-term life-history study on the species. Each bird is fitted with a coloured leg ring, as well as a metal ring and various body size measurements and samples are also taken to assess its condition and health. By catching these birds we have been able to identify issues affecting them, such as illegal shooting and lead poisoning (Newth et al. 2011, Newth et al. 2012). This information helps to inform subsequent conservation measures taken to reduce the scale of these threats.

     Ring combinations used
    Yellow leg rings (black lettering) Red leg rings (white lettering) Orange leg rings (black lettering)
    Alpha/alpha/alpha AJA – VZZ AAA – BLZ ZAA – ZZZ
    Numeric/alpha/alpha 3AA – 9ZZ
    Alpha/alpha/numeric FA3 – ZZ9
    Numeric/numeric/alpha 31A – 99Z
    Alpha/numeric/numeric A33 – Z99
    Alpha/numeric/alpha A3A – Y9Z

    If you see any colour-marked Whooper Swans with these combinations please send your sightings to colourmarkedwidlfowl@wwt.org.uk

    Project partners

    We work with the Icelandic Institute of Natural History, the Icelandic Research Council, the Irish Whooper Swan Study Group, Olafur Einarsson, Sverrir Thorstensen, the University College Cork and the University of Iceland.

    References

    Garðarsson, A. 1991. Movements of Whooper Swans Cygnus cygnus neckbanded in Iceland. In: Sears, J. & P.J. Bacon (eds.). Proceedings of the 3rd IWRB International Swan Symposium, Oxford, 1989. Wildfowl Special Supplement No. 1: 189-194.

    McElwaine, J.G., J.H. Wells & J.M. Bowler. 1995. Winter movements of Whooper Swans visiting Ireland: preliminary results. Irish Birds 5: 265-78.

    Mitchell, C. & M. Ogilvie. 1997. Fifty years of wildfowl ringing by the Wildfowl & Wetlands Trust. Wildfowl 47: 240-247.

    Newth, J., K. Colhoun, Ó. Einarsson, R. Hesketh, J.G. McElwaine, S. Thorstensen, A. Petersen, J. Wells & E.C. Rees. 2007. Winter distribution of Whooper Swans (Cygnus cygnus) ringed in four geographically discrete regions in Iceland between 1988 and 2006: an update. Wildfowl 57: 98-119. Download.

    Rees, E.C. & J.M. Bowler. 1996. Fifty years of swan research and conservation by the Wildfowl & Wetlands Trust. Wildfowl 47: 248-263. Download.

    Rees, E.C., K. Colhoun,  Ó. Einarsson, J.G. McElwaine, Æ. Petersen & S. Thorstensen. 2002. Whooper Swan Cygnus cygnus. In: Wernham, C.V., M.P. Toms, J.H. Marchant, J.A. Clark, G.M. Siriwardena & S.R. Baillie (eds.) The Migration Atlas: Movements of the Birds of Britain and Ireland. Pp. 154-157. T. & AD Poyser, London.

  • Survey results

    International Swan Census reports: See the Reports & newsletter page

    Wetland Bird Survey Alerts

    Wetland Bird Survey annual report

    Relevant publications

    Griffin, L., E.C. Rees & B. Hughes. 2010. The Migration of Whooper Swans in Relation to Offshore Wind Farms. WWT Final Report to COWRIE Ltd, WWT, Slimbridge.

    Kear, J. 2005. Ducks, geese & swans. Oxford University Press.

    Robinson, J.A., K. Colhoun, J.G. McElwaine & E.C. Rees. 2004. Whooper Swan Cygnus cygnus (Iceland population) in Britain and Ireland 1960/61 – 1999/2000. Waterbird Review Series, The Wildfowl & Wetlands Trust/Joint Nature Conservation Committee, Slimbridge. Download

    Other relevant material

    BirdLife International Species factsheet

    British Trust for Ornithology: Bird Facts

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