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 2016)
Breeding success (GSMP survey)
200,000 – 250,000 individuals
Long-term trend (1988/89 – 2013/14): 15% increase
Ten-year trend (2003/04 – 2013/14): 46% 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 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 2015/16 [August 2016]
The winter of 2015/16 marked the 31st consecutive winter that experienced volunteer observers assessed the breeding performance of Dark-bellied Brent Geese (for methods see Hall 2008). Geese were aged at 69 localities within 12 estuaries or coastal areas, from Lindisfarne, Northumberland to the Exe Estuary in Devon (Figure 1 & Table 1). Data were collected between 20 September 2015 and 8 March 2016.
Of the 96 flocks assessed, the majority were aged in November (28.6%) with 19.8% aged in October, 17.6% in January and 15.4% in December. Fewer flocks were aged in February (13.2%), March (4.4%) and September (2.0%) (Table 2).
A total of 40,060 geese were aged; a similar number to those aged in 2014/15, but 33.6% lower than the previous five-year mean. The largest sample came from the North Lincolnshire Coast with 12,231 geese aged. Samples of more than 2,000 birds were received from the Dengie Estuary (8,376), in North Norfolk (5,474), Chichester Harbour (4,152), the Blackwater Estuary (2,674) and the Thames Estuary (2,635). Sample sizes of fewer than 2,000 birds were from the Solent (1,174), the Crouch Estuary (1,083), the Exe Estuary (892), Stour Estuary (745), Hamford Water (606) and Lindisfarne (18).
The overall percentage of young birds was 0.9% and, of the 110 broods recorded, the mean brood size was 1.57 (±0.09 SE) young per successful pair (Figure 2).
Figure 1. Sites in the UK at which Dark-bellied Brent Geese were aged during winter 2015/16. See Table 1 for key to 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 20/09/2015 17/01/2016 7 4 892 0.8 – 2 The Solent 24/10/2015 16/01/2016 4 3 1,174 1.1 1.56 0.34 3 Chichester Harbour 18/10/2015 28/01/2016 15 11 4,152 0.8 1.68 0.23 4 Thames Estuary 04/10/2015 02/02/2016 3 3 2,635 1.6 1.40 0.19 5 Crouch Estuary 02/12/2015 18/12/2015 2 1 1,083 2.0 1.40 0.24 6 Dengie Estuary 11/11/2015 25/12/2015 4 2 8,376 0.8 1.36 0.23 7 Backwater Estuary 06/12/2015 23/12/2016 2 1 2,674 1.4 – – 8 Hamford Water 11/11/2015 05/02/2016 4 4 606 0.8 – – 9 Stour Estuary 01/11/2015 09/12/2015 5 4 745 1.47 – – 10 North Norfolk Coast 14/10/2015 03/03/2016 18 16 5,474 0.6 1.60 0.19 11 North Lincs Coast 02/10/2015 08/03/2016 31 19 12,231 0.7 1.42 0.16 12 Lindisfarne 30/10/2015 30/10/2015 1 1 18 66.6 4.0 0.58 Total 20/09/2015 08/03/2016 96 69 40,060 0.9 1.57 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, 1985/86-2015/16. 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 2% in all months except September (37.5%), however the sample size in September was very small compared to the other months (Table 2). The mean brood size of successful pairs peaked in October at 1.94 and ranged between 1.0 and 1.47 during other months.
Table 2. The percentage of young and mean brood size of Dark-bellied Brent Geese in the UK during winter 2015/16. Not included are 8 birds were aged in September with 3 of these being young birds.
Percentage of young Mean brood size Month % n Mean SE n September 37.5 8 1 October 1.4 4,612 1.94 0.20 18 November 0.7 12,945 1.44 0.13 31 December 1.5 8,684 1.30 0.13 14 January 0.6 6,118 1.47 0.23 16 February 1.0 5,360 1.38 0.18 12 March 0.7 2,263 1.0 – 4 Total 0.9 40,060 1.57 0.09 96
The vast majority of flocks (90%, n = 86) held less than 5% young (Figure 3), thus very few flocks held >5% young; seven flocks (7.3%) held 5-15% young and the three remaining categories (15-30% young to >50% young) each held approximately 1% of the total number of flocks sampled.
Figure 3. Frequency distribution of the percentage of young in individual flocks (n=91) of Dark-bellied Brent Geese in the UK during winter 2015/16.
The percentage of young was highest amongst flocks of fewer than 100 geese (4.1%) and was lowest amongst flocks of 1,000-1,999 geese (0.7%). Mean brood size ranged from 1.36 to 2.0 young per successful pair (Figure 4).
Figure 4. The percentage young (blue column) and mean brood sizes (red circles) of Dark-bellied Brent Geese in the UK flocks of different sizes during winter 2015/16. Sample sizes (number of flocks) are represented on the graph.
Dark-bellied Brent Geese were recorded using five main habitat types in 2015/16; water, intertidal (including Enteromorpha spp., and Zostra), saltmarsh, grass and cereal fields (including arable stubbles and oilseed rape). The highest percentage of young was seen amongst flocks feeding on intertidal habitats (1.4%). Mean brood size ranged from 1.20 (±0.20 SE) to 2.0 (±0.19 SE).
Figure 5. The percentage young (blue column) and mean brood sizes (red circles) of Dark-bellied Brent Geese in the UK recorded in different habitat groups during winter 2015/16. 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 2015 was well below the previous ten year average (11.8% ± 2.91 SE), and 22.1% lower than the previous year. Mean brood size was lower than in 2014/15 and also below the previous ten-year mean (2.26 ± 0.14 SE).
No data on breeding success among birds wintering outside the UK are available at the current time, so it is uncertain how representative the estimates from UK are. However, reports from monitoring stations along the breeding grounds in Arctic Russia indicate that rodent numbers were generally low in 2015 (Soloviev & Tomkovich 2016). As breeding success of Dark-bellied Brent Geese is greatly influenced by interactions between rodent abundance and predator pressure, the low rodent abundance and high numbers of Arctic Fox may explain why the geese had a poor breeding season in 2015.
As ever, thanks are extended to the many volunteer counters who provided Dark-bellied Brent Goose age counts.
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.
Soloviev, M & P Tomkovich. (Eds.) 2016. Online database: http://www.arcticbirds.ru/ Accessed June 2016.
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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