speciesaccounts_darkbelliedbrentgooseDark-bellied Brent Goose

Branta bernicla bernicla

The Dark-bellied Brent Goose breeds along the Arctic coasts of Russia and winters exclusively along the coasts of Western Europe, the majority concentrated at sites along the Atlantic west coast of France, the south and east coasts of England, southwest Netherlands and the Wadden Sea.

In England, Dark-bellied Brent Geese usually occur in largest numbers at The Wash and the Thames Estuary.

  • 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)

    * assessed at species level Branta bernicla

    Least Concern*†

    B2b

    Least Concern (Europe and EU27)*

    Annex II (Part B)

    Amber

    not huntable

    † Brent Goose Branta bernicla is listed as ‘Least Concern’ by IUCN. The Red List assessment of sub-species is not routinely undertaken, however, an assessment of Dark-bellied Brent Goose Branta bernicla bernicla was undertaken as part of the UK’s Birds of Conservation Concern 3; the subspecies was evaluated as ‘Vulnerable’.

    Population Status

    Flyway population size (CSR 6; Wetlands International 2015)

    GB estimate (Musgrove et al. 2011)

    GB trend (SUKB 2017)

    Breeding success (GSMP survey)

    200,000 – 250,000 individuals

    91,000  individuals

    Long-term trend (1989/90 – 2014/15): 17% increase
    Ten-year trend (2004/05 – 2014/15): 42% increase

    Marked cyclic fluctuation, varying between 0% and 31%

    Summary statistics

    Annual estimates of the percentage of young (%) and mean brood size (young per successful pair) of Dark Bellied Brent Goose in Britain, 2003/04-2017/18.

    Season Percentage of young (%) Mean brood size
    2017/18 1.0 1.91
    2016/17 8.6 1.96
    2015/16 0.9 1.57
    2014/15 23.0 2.77
    2013/14 15.4 2.49
    2012/13 3.1 1.61
    2011/12 16.2 2.26
    2010/11 12.7 2.7
    2009/10 5.3 1.83
    2008/09 1.1 1.74
    2007/08 11.0 2.60
    2006/07 2.0 1.62
    2005/06 28.4 2.76
    2004/05 11.9 2.33
    2003/04 10.0 2.14
    Reference

    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.

  • The Dark-bellied Brent Goose breeds along the Arctic coasts of the Yamal, Gydan and Taimyr Peninsulas and the islands of the Kara Sea. It winters exclusively along the coasts of Western Europe, the majority concentrated at sites along the Atlantic west coast of France, the south and east coasts of England, southwest Netherlands and the Wadden Sea (Ebbinge et al. 1999). The migration route follows the coastline from northern Russia, through the White Sea and Baltic Sea, and along the North Sea coast, the English Channel and the French Atlantic coast.

    flyway map brent_db

    Flyway of the Dark-bellied Brent Goose

    On arrival in western Europe, some Dark-bellied Brent Geese initially stage on the Danish and Schleswig-Holstein coasts of the Wadden Sea, or at Foulness, Essex. From Foulness, birds disperse to winter in other parts of southern Britain, and to France. Whilst most birds depart wintering sites in March for pre-migration fattening on the Wadden Sea, up to 10,000 now stage on the Wash, eastern England, with much smaller numbers in north Norfolk, north Kent, the Stour Estuary and the Beaulieu Estuary (Ward 2004).

    Since 1973, associated with the rapid population growth, Dark-bellied Brent Geese have made increasingly extensive use of inland habitats in the UK for foraging, including grassland, winter cereals and oilseed rape. For most sites, a sequential pattern of habitat use now occurs as birds successively deplete Zostera, Enteromorpha and finally saltmarsh food resources prior to switching to inland habitats. By mid winter, a large proportion of total feeding time is spent inland at most key sites in the UK. Most birds return to saltmarshes to exploit fresh growth of more natural foods at their spring staging sites in western Europe (Ward 2004).

    In the UK, conflict with agriculture arises in Norfolk, Suffolk, Essex and the south coast of England when Dark-bellied Brent Geese forage on winter cereals and oilseed rape. To lessen the conflict locally, nature reserves are managed for these birds, providing alternative feeding areas often in combination with scaring operations outside.

    The breeding success of Dark-bellied Brent Geese has previously been shown to follow a three-year cycle of ‘good’, ‘poor’ and ‘variable’ success (Dhondt 1987) and is greatly influenced by interactions between lemming abundance, predator pressure and other factors such as weather. Between the mid 1990s and 2005, whilst there was still considerable annual variation in Brent breeding success, the pattern shifted away from a predictable three-yearly cycle, and there were fewer than expected good breeding seasons. This suggests that the connection between rodent abundance and breeding success may no longer function in the same way, or that rodent abundance is no longer following such a predictable pattern.

    References

    Dhondt, A.A. 1987. Cycles of lemmings and Brent Geese Branta b. bernicla: a comment on the hypothesis of Roselaar and Summers. Bird Study 34: 151-154.

    Ebbinge, B.S., C. Berrevoets, P. Clausen, B. Ganter, K. Gunther, K. Koffijberg, R. Maheo, M. Rowcliffe, A.K.M. St Joseph, P. Sudbeck & E.E. Syroechkovsky Jnr. 1999. Dark-bellied Brent Goose Branta bernicla bernicla. In: Madsen, J., G. Cracknell & A.D. Fox (eds.). 1999. Goose populations of the Western Palearctic. A review of status and distribution. Wetlands International Publication no. 48, Wetlands International, Wageningen,The Netherlands/National Environmental Research Institute, Ronde, Denmark.

    Ward, R.M. 2004. Dark-bellied Brent Goose Branta bernicla bernicla in Britain 1960/61 – 1999/2000. Waterbird Review Series, The Wildfowl & Wetlands Trust/Joint Nature Conservation Committee, Slimbridge.

  • Wetland Bird Survey

    The abundance of the Dark-bellied Brent Goose population in the UK is monitored through the Wetland Bird Survey (WeBS). The results from the survey are published in an annual report (see the WeBS website for details).

    GSMP age assessments

    Age assessments of Dark-bellied Brent Geese are undertaken at various sites in Britain, with counts carried out between September and March. 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 of the age assessments can be found on the ‘Latest results’ tab.

    Find out more about age assessments

  • Results for 2017/18 [September 2018]

    Abundance

    The abundance of Dark-bellied Brent Geese in the UK during 2016/17 was monitored through the Wetland Bird Survey (WeBS). Results are available on WeBS Report Online.

    Breeding success

    The winter of 2017/18 marked the 33rd consecutive winter that experienced volunteer observers assessed the breeding performance of Dark-bellied Brent Geese (for methods see Hall 2008). Geese were aged at 86 localities within eleven estuaries or coastal areas along the south and east coast of England, from North Lincolnshire to Portland Harbour in Dorset (Figure 1 & Table 1). Data were collected between 23 September 2017 and 26 March 2018.

    A total of 42,706 geese were aged, an increase on the previous year when 24,804 were aged. The largest samples came from the North Lincolnshire Coast (7,801 birds aged), Chichester Harbour (5,942), North Norfolk (5,886) and Portland Harbour (5,865) (Figure 1 & Table 1). At all other sites, fewer than 4,000 birds were aged. Of the 131 flocks assessed, the majority were aged in November (28.2%), January (24.4%) and December (21.4%) with 12.2% aged in October, 7.6% in February and 3.1% in September and March.

    The overall percentage of young was 1.0% and of the 157 broods recorded the mean brood size was 1.91 (±0.09 SE) young per successful pair (Figure 2 & Table 1).

    The percentage of young in flocks remained fairly consistent throughout the winter and below 2.0% in all months (Table 2). The mean brood size of successful pairs peaked in February at 2.23 (±0.34 SE) and ranged between 2.20 (±0.20 SE) and 1.63 (±0.15 SE) during other months.

     

    Figure 1. Sites in the UK at which Dark-bellied Brent Geese were aged during winter 2017/18. See Table 1 for a key to the sites.

    Table 1. Numbers of Dark-bellied Brent Geese aged at UK estuaries and coastal areas in winter 2017/18.

    Estuary Sample flocks Number of sites Total aged Percentage of young Mean brood size SE
    First Last Number of flocks
    1 Portland Harbour 19/10/2017 15/11/2017 3 1 5,865 0.2 1.8 0.26
    2 The Solent 08/11/2017 08/11/2017 1 1 459 0.0
    3 Langstone Harbour 27/09/2017 16/11/2017 8 7 2,252 0.3 2.00 1.00
    4 Chichester Harbour 31/10/2017 21/12/2017 19 17 5,942 1.0 2.07 0.2
    5 Crouch Estuary 22/02/2017 15/02/2018 5 4 4,657 1.0 1.43 0.23
    6 Blackwater Estuary 23/01/2017 23/02/2018 1 1 690 0.4 1.00 0.00
    7 Hamford Water 27/10/2017 22/02/2018 12 2 3,962 0.8 1.50 0.26
    8 Stour Estuary 12/01/2017 12/02/2017 4 3 368 1.1 1.00 0.00
    9 North Norfolk 23/09/2017 10/03/2018 20 17 5,886 1.6 2.38 0.36
    10 The Wash 25/09/2017 26/03/2018 21 12 4,824 0.5 1.50 0.18
    11 North Lincolnshire Coast 01/10/2017 07/03/2018 37 21 7,801 1.6 2.14 0.17
    Total 23/09/2017 26/03/2018 131 86 42,706 1.0 1.91 0.09

     

    Figure 2. The percentage of young (blue columns) and mean brood size (red circles) of Dark-bellied Brent Geese recorded in the UK, 1985/86–2017/18. No brood size data were collected in 1985/86, 1986/87 or 1989/90.

     

    Table 2. Monthly variation in the percentage of young and mean brood size of Dark-bellied Brent Geese in the UK during winter 2017/18.

    Month Percentage young Mean brood size
    % n Mean SE n
    September 0.4 559   –
    October 2.0 3,756 1.89 0.45 9
    November 0.4 13,441 2.20 0.20 35
    December 1.1 8,300 1.95 0.15 40
    January 1.1 11,654 1.63 0.15 56
    February 1.0 4,150 2.23 0.34 13
    March 1.3 846 2.00 0.70 4
    Total 1 42,706 1.91 0.09 157

    Discussion

    Results from age assessments made at wintering sites in the UK indicate that the breeding success of Dark-bellied Brent Geese in 2017 was low and well below the previous ten-year mean (9.7% ± 2.30 SE). The mean brood size was slightly lower than in 2016/17 and below the previous ten-year mean (2.2% ± 0.13 SE).

    During the most recent three winters, the percentage of young amongst wintering flocks has remained below 10% and the population appears to have skipped a good breeding season, which is usually expected with the three-yearly cycle of lemming and predator abundance which greatly influences Dark-bellied Brent Goose breeding success.

    At the time of writing, no data were available on the breeding success of Dark-bellied Brents wintering elsewhere along the flyway, so it is uncertain how representative the estimates from the UK are of the population as a whole.

    Reports from monitoring stations in the breeding grounds in Arctic Russia (Soloviev & Tomkovich 2018) suggest that weather conditions were far from suitable, with the air temperature in May 2017 being lower than the average for the last 38 years and for the last 15 years in June. A combination of poor weather during the incubation and early gosling rearing stages, and prolonged spells of snow reported in most days of June, is likely to be the main contributing factor to the very poor breeding season for the Dark-bellied Brent Geese wintering in the UK in 2017.

    Acknowledgements

    As always our thanks go to the network of dedicated GSMP volunteers for their help with collecting age assessments.

    References

    Hall, C. 2008. The breeding success of Dark-bellied Brent Geese Branta bernicla bernicla in 2007, as assessed in the UK. Wildfowl & Wetlands Trust Report, Slimbridge. Download

  • Previous annual results will be archived here. Annual age assessment reports for 1985-2007 inclusive can be found on the Reports & newsletter page.

    2016/17 Results

    2015/16 Results

    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

  • Survey results

    Wetland Bird Survey Alerts

    Wetland Bird Survey annual report

    Relevant publications

    Ebbinge, B.S., J. Blew, P. Clausen, K. Günther, C. Hall, C. Holt, K. Koffijberg, S. Le Dréan-Quénec’hdu, R. Mahéo & S. Pihl. 2013. Population development and breeding success of Dark-bellied Brent Geese Branta. b. bernicla from 1991-2011. Wildfowl Special Issue: 3: 74-98. Download

    Ward, R.M. 2004. Dark-bellied Brent Goose Branta bernicla bernicla in Britain 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: BirdFacts

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