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 Wash and the Thames Estuary.
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 (Europe and EU27)*
Annex II (Part B)
† 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 6; Wetlands International 2015)
GB estimate (Musgrove et al. 2011)
GB trend (SUKB 2017)
Breeding success (GSMP survey)
200,000 – 250,000 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%
Annual estimates of the percentage of young (%) and mean brood size (young per successful pair) of Dark Bellied Brent Goose in Britain, 2003/04-2015/16.
Season Percentage of young (%) Mean brood size 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
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 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 2016/17 [August 2017]
The winter of 2016/17 marked the 32nd consecutive winter that experienced volunteer observers assessed the breeding performance of Dark-bellied Brent Geese (for methods see Hall 2008). Geese were aged at 74 localities within ten estuaries or coastal areas, from the Humber Estuary in Lincolnshire to the Exe Estuary in Devon (Figure 1 & Table 1). Data were collected between 23 September 2016 and 21 March 2017.
Of the 113 flocks assessed, the majority were aged in January (26.6%), December (24.5%) and November (16.7%) with 14.7% aged in October, 13.2% in February, 3.9% in March and 0.4% in September.
A total of 24,804 geese were aged. The largest samples came from North Norfolk, North Lincolnshire Coast and The Wash with 6,662, 4,358 and 4,160 geese aged, respectively (Table 1). At all other sites, fewer than 3,000 birds were aged.
The overall percentage of young was 8.6% and of the 277 broods recorded the mean brood size was 1.96 (±0.06 SE) young per successful pair (Figure 2 & Table 1).
Figure 1. Sites in the UK at which Dark-bellied Brent Geese were aged during winter 2016/17. See Table 1 for key sites.
Table 1. Numbers of Dark-bellied Brent Geese aged at UK estuaries and coastal areas in winter 2015/16.
Sample flocks Estuary First count Last count number of flocks Number of sites Total aged Percentage of young (%) Mean brood size SE 1 Exe Estuary 19/11/2016 19/02/2017 7 6 1,150 6.9 – – 2 Langstone Harbour 13/09/2016 21/03/2017 14 12 1,654 3.8 1.90 0.15 3 Chichester Harbour 17/12/2016 09/02/2017 16 12 1,380 6.9 1.75 0.11 4 Thames Estuary 12/10/2016 17/10/2016 5 3 2,135 9.0 2.31 0.12 5 Hamford Water 25/10/2016 17/02/2017 8 5 1,706 16.1 1.89 0.31 6 Stour Estuary 16/01/2016 16/01/2017 4 2 990 7.6 – – 7 North Norfolk 26/10/2016 07/03/2017 14 13 6,662 6.5 1.77 0.10 8 The Wash 30/09/2016 07/03/2017 20 9 4,160 7.4 – – 9 North Lincolnshire Coast 17/11/2016 01/03/2017 24 11 4,358 13.0 2.13 0.18 10 Humber Estuary 14/01/2017 14/01/2017 1 1 609 6.6 – – Total 23/09/2016 12/03/2017 113 74 24,804 8.6 1.96 0.06
Figure 2. The percentage of young (blue columns) and mean brood size (red circles) of Dark-bellied Brent Geese recorded in the UK, 1985/86–2016/17. No brood size data were collected in 1985/86, 1986/87 or 1989/90.
The percentage of young in flocks remained fairly consistent throughout the winter and below 11.1% in all months (Table 2). The mean brood size of successful pairs peaked in October at 2.26 (±0.12 SE) and ranged between 1.77 (±0.20 SE) and 2.06 (±0.20 SE) during other months.
Table 2. Monthly variation in the percentage of young and mean brood size of Dark-bellied Brent Geese in the UK during winter 2016/17.
Percentage of young Mean brood size Month % n Mean SE n September 0 101 – – – October 7 3,638 2.26 0.12 16 November 8.3 4,145 2.06 0.20 18 December 11.1 6,075 1.83 0.11 24 January 7.2 6,596 1.78 0.09 30 February 9.7 3,273 1.77 0.20 17 March 6.5 976 1.82 0.33 6 Total 8.6 24,804 1.96 0.06 113
The percentage of young within individual flocks varied from 0% to 53.8%. Flocks most frequently (47.8%, n = 54) held between 5-15% young, whilst 26.5% (n = 30) contained <5%, of which 15 flocks held no young at all. Notably fewer flocks held above 15% young: 18.6% (n = 21) held between 15-30%; five flocks (4.4%) contained 30-50%; and three flocks (2.7%) held >50%.
Figure 3. Frequency distribution of the percentage of young in individual flocks (n=113) of Dark-bellied Brent Geese in the UK during 2016/17.
The percentage of young was highest amongst flocks of fewer than 100 geese (12.1%) and was lowest amongst flocks of 1,000-1,999 geese (6.3%). Mean brood size ranged from 1.7 (±0.12 SE) to 2.3 (±0.14 SE) young per successful pair (Figure 4). No brood sizes were recorded in flocks of 1,000-1,999 birds.
Figure 4. The percentage of young (blue column) and the mean brood size (red circles) of Dark-bellied Brent Geese in the UK in flocks of different sizes during winter 2016/17. Sample sizes (number of flocks) are given above the columns.
Dark-bellied Brent Geese were recorded using five main habitat types in 2016/17; water, intertidal (including Enteromorpha spp. and Zostera), saltmarsh, grass and cereal fields (including arable stubbles and oilseed rape). The highest percentage of young was seen amongst flocks on water and feeding on cereals (11.2% and 11.0%, respectively). Mean brood size ranged from 1.75 (±0.11 SE) to 2.13 (±0.08 SE).
Figure 5. The percentage of young (blue column) and mean brood sizes (red squares) of Dark-bellied Brent Geese in the UK recorded in different habitat groups during winter 2016/17. Sample sizes (total number aged) are given above the columns.
Results from age assessments made at wintering sites in the UK indicate that the breeding success of Dark-bellied Brent Geese in 2016 was 7.7% higher than the previous year, although it remained below the previous ten-year mean (9.7% ± 2.43 SE). Mean brood size was also higher than in 2015/16 but below the previous ten-year mean (2.1% ± 0.14 SE).
The results during 2016 follow a poor breeding performance in 2015 (0.9% young) and a good breeding season in 2014 (23.0% young), and the previous three years (2011/12 to 2013/14) also followed a similar pattern, perhaps suggesting some return to the three-year cycle of lemming and predator abundance which greatly influences Dark-bellied Brent Goose breeding success.
No data on breeding success among birds wintering outside the UK are available at the current time, so it is uncertain how representative are the estimates from the UK. Reports from monitoring stations in the breeding grounds in Arctic Russia suggest that rodent abundance was relatively low in 2016 and predators such as Arctic Fox were scarce after record high abundance in 2015 (Soloviev & Tomkovich 2017). Breeding success of Dark-bellied Brent Geese is greatly influenced by interactions between rodent abundance and predator pressure. Usually when rodent abundance is low, breeding success is reduced as Arctic Foxes turn their attention to goslings; however, with low numbers of Arctic Fox reported in 2016 as well as low rodent abundance, this may explain why the geese had a slightly better breeding season than the previous year.
As always our thanks go to the network of dedicated GSMP volunteers: the Exe Estuary Observers Group, Maureen Gibson, Peter Hughes, Nigel Lound, Rob Lucking, Julian Novorol, Wes Smith, John Walker, David and Pat Wileman and Derek and Glenys Wood for their help with collecting age assessments.
Soloviev, M & P Tomkovich. (Eds.) 2017. Online database: http://www.arcticbirds.ru/ Accessed June 2017.
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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