Dark-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 Thames Estuary, The Wash and Chichester Harbour.
Global status (IUCN Red List of Threatened Species) Least Concern*† African-Eurasian Waterbird Agreement (AEWA) B2b European status (European Red List of Birds) Least Concern (Europe and EU27)* The Birds Directive (European Commission) Annex II (Part B) UK status (Birds of Conservation Concern) Amber UK quarry species (Wildlife & Countryside Act 1981) not huntable * assessed at species level Brent Goose Branta bernicla † 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’.
Flyway population size (CSR 8; Wetlands International 2020) 211,000 individuals UK estimate (APEP 4) 98,500 individuals GB estimate (Frost et al. 2019) 98,000 individuals UK trend (Frost et al. 2021) 25-year trend (1993/94-2018/19) = 23% decrease
10-year trend (2008/09-2018/19) = 11% increase
Table 1. Annual estimates of the percentage of young (%) and mean brood size (young per successful pair) of Dark Bellied Brent Goose in Britain, 2003/04-2020/21.
Season Percentage of young (%) Mean brood size 2020/21 9.1 2.35 2019/20 13.1 2.26 2018/19 8.0 1.88 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
Frost, T., G.E. Austin, R.D. Hearn, S. McAvoy, A. Robinson, D.A. Stroud, I. Woodward & S.R. Wotton. 2019. Population estimates of wintering waterbirds in Great Britain. British Birds 112: 130-145.
Frost, T.M., N.A. Calbrade, G.A. Birtles, C. Hall, A.E. Robinson, S.R. Wotton, D.E. Balmer & G.E. Austin. 2021. Waterbirds in the UK 2019/20: The Wetland Bird Survey. BTO, RSPB and JNCC, in association with WWT. British Trust for Ornithology, Thetford.
Wetlands International. 2021. Waterbird population estimates. Retrieved from http://wpe.wetlands.org/ September 2021.
Dark-bellied Brent Goose data for Britain presented in Table 1 (Percentage of young/Mean brood size) are licensed under the Open Government Licence 3.0 except where otherwise stated.
When you use information from this report under the Open Government Licence you must include the following attribution:
Contains Goose & Swan Monitoring Programme (GSMP) data from “WWT. 2021. Goose & Swan Monitoring Programme: survey results for Dark-bellied Brent Goose Branta bernicla bernicla. WWT/JNCC/NatureScot, Slimbridge” retrieved from https://monitoring.wwt.org.uk/our-work/goose-swan-monitoring-programme/species-accounts/dark-bellied-brent-goose/ © copyright and database right 2021. The GSMP is organised by the Wildfowl & Wetlands Trust (WWT) in partnership with the Joint Nature Conservation Committee (JNCC) and NatureScot with fieldwork conducted by volunteers.
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 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.
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 2020/21 [September 2021]
2020/21 marked the 36th consecutive season that experienced volunteer observers assessed the breeding performance of Dark-bellied Brent Geese wintering in Britain (for methods see Hall 2008).
Geese were aged at 100 locations within ten estuaries or coastal sites along the south and east coasts of England from the North Lincolnshire coast to The Solent in Hampshire (Figure 1 & Table 1). Data were collected between 13 October 2020 and 23 February 2021. Due to Covid-19 restrictions, counts were only undertaken where counters were legitimately able to do so: such as undertaken as part of their permitted daily exercise or where surveys were carried out by reserve staff.
In total, 20,827 geese, within 87 flocks, were aged across the season which represents an increase of 11.1% on the previous year when 18,738 birds were aged. The largest samples were assessed at Langstone Harbour (6,427 birds aged), Southampton Water (3,728) and North Norfolk (3,681) (Table 1 & Figure 1). At all other sites, fewer than 3,000 birds were aged. Mean brood size data was collected at four of the estuaries/coastal areas.
The overall percentage of young recorded amongst flocks was 9.1% and, of the 74 broods recorded, the mean brood size was 2.35 (± 0.15 SE) young per successful pair (Table 1 & Figure 2).
Across the season, the percentage of young in flocks peaked at 10.7% in November and ranged between 7.4% and 9.6% during other months (Table 2). The mean brood size of successful pairs peaked at 2.50 (± 0.25 SE) in November and ranged between 2.00 (± 0.41 SE) and 2.42 (± 0.40 SE) during the other months.
Figure 1. Estuaries / coastal sites in the UK at which Dark-bellied Brent Geese were aged during winter 2020/21. See Table 1 for a key to the estuaries / coastal sites.
Table 1. Numbers of Dark-bellied Brent Geese aged at UK estuaries and coastal areas in winter 2019/20
Estuary Sample flocks Number of sites Total aged Percentage of young Mean brood size SE Number of broods First Last Number of flocks 1 The Solent 10/12/2020 10/12/2020 1 1 30 40.0 2 Southampton Water 03/11/2020 22/11/2020 23 23 3,728 9.9 3 Portsmouth Harbour 10/11/2020 22/11/2020 2 2 235 6.0 4 Langstone Harbour 17/10/2020 23/02/2021 12 25 6,427 8.9 5 Chichester Harbour 13/10/2020 20/01/2021 15 15 2,913 7.3 6 Blackwater Estuary 30/11/2020 30/11/2020 1 1 4 100 7 Stour Estuary 24/11/2020 29/11/2020 3 3 580 13.1 1.50 0.05 3 8 Hamford Water 30/10/2020 29/01/2021 7 7 322 23.0 3.83 0.47 6 9 North Norfolk Coast 16/10/2020 16/02/2021 13 13 3,681 9.4 1.75 0.07 51 10 North Lincolnshire Coast 17/10/2020 21/02/2021 10 10 2,907 7.3 1.72 0.11 14 Total 13/10/2020 23/02/2021 87 20,827 20,827 9.1 2.35 0.15 74
Figure 2. The percentage of young (blue columns) and mean brood size (red circles) of Dark-bellied Brent Geese recorded in Britain, 1985/86–2020/21. No brood size data were collected in 1985/86 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 2020/21.
Month Percentage young Mean brood size % Number of flocks Number aged Mean SE Number of broods October 8 9 1,440 2.42 0.4 12 November 10.7 30 5,556 2.5 0.25 30 December 9.6 19 5,095 2.29 0.27 17 January 7.4 22 5,106 2.17 0.48 6 February 8.7 7 3,630 2 0.41 9 Total 9.1 87 20,827 2.35 0.15 74
Results from age assessments made at wintering sites in Britain suggest that the Dark-bellied Brent Geese had a below average breeding season in 2020: the percentage young recorded amongst flocks (9.1%) was lower than the previous year (13.1% in 2019/20) and lower than the previous ten-year mean (2010/11–2019/20; 10.2% ± 2.28 SE). However, the mean brood size of successful pairs during 2020 (2.35) was slightly higher than the previous year (2.26 in 2019/20) and higher than the previous ten-year mean (2010/11–2019/20; 2.17 ± 0.12 SE).
Reports from monitoring stations in the breeding grounds in Arctic Russia suggest that the 2020 breeding season was generally average and conditions were seemingly good for breeding geese (Soloviev & Tomkovich 2020). The weather was reportedly good with many areas experiencing above average temperatures, and rodents were reported in abundance at some monitoring stations: in years with high rodent numbers, predators are able to exploit this resource and prey less on eggs and young goslings.
At the time of writing, no data were available on the breeding success of Dark-bellied Brent Geese wintering elsewhere along the flyway; therefore, it is uncertain how representative the estimates from Britain are of the population as a whole.
As always, our grateful thanks go to the network of dedicated GSMP volunteers for undertaking the age assessments.
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
Soloviev, M. & P.S. Tomkovich (Eds.) 2020. Arctic Birds: an international breeding conditions survey. Online database: http://www.arcticbirds.net/. Accessed 08/06/2021.
Previous annual results will be archived here. Annual age assessment reports for 1985-2007 inclusive can be found on the Reports & newsletter page.
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
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