(Thanks to the Irish Brent Goose Research Group for much of this information)
Brent geese are a small (<2kg) long-distance migratory goose with a circumpolar breeding distribution and temperate wintering distribution. Of the 8 recognised flyway populations, the flyway population we are primarily focussed on breeds in eastern High Arctic Canada, migrates through and stages in Greenland and western Iceland and winters in north-west Europe, chiefly Ireland but also western Britain south to northern France. Other groups overwinter in the Exe Estuary and migrate through Russia, and Siberia to the Russian Arctic. Another sub-species (known locally as Brant Geese) migrate along flyways from Mexico to the Alaska.
October – March: Ireland (also western Britain, northern France and Jersey)
April – May: Western Iceland
June – August: Arctic Canada (Ellesmere, Axel Heiberg, Devon and Bathurst Islands primarily)
September: Western Iceland
Diet and feeding ecology
Like all brent goose populations this species is amongst the most resource-specific of all geese; the main food plant is inter-tidal eel-grass Zostera spp.. Other inter-tidal and coastal vegetation is consumed during the year including green algaes (Enteromorpha and Ulva spp.) and saltmarshes grasses (e.g. Puccinellia). In the non-breeding season there is an increasing tendency for terrestrial grassland feeding (mainly Agostris and Poa) on farmland and amenity grasslands. In the breeding grounds a variety of arctic grasses and sedges are consumed.
Knowledge on the degree of fidelity to breeding sites is limited by the lack of study of marked individuals in the breeding range in consecutive years. Intensive marking throughout the range and observation at sites primarily in western Iceland and Ireland have revealed a high degree of site fidelity.
Generally occurs at low densities in the breeding range but through much of the year form flocks comprising singletons, pairs and family units. The family units, comprising 1 – 6 young, remain together from the breeding season until the spring staging period about 9 months later.
Facts and figures
Population size has ranged from 10,000 (1960s) to c. 40,000 (2010). Annual productivity fluctuates widely from 0.1% to almost 25%. Mean brood size in good years 2-3 goslings/pair (age and brood size estimates made in autumn). Heaviest birds (peak mass in late spring: c. 2.2kg for males and females). Based on small sample, mean clutch size 4 eggs, laid mid-June, peak hatching early-mid July.
(Thanks to the Norwegian Polar Institute for the following information)
The brent goose is somewhat smaller than the barnacle goose. Brent geese normally do not fly in the typical V-formation used by other geese, but in irregular masses or lines.
There are several subspecies of brent geese, each of which has somewhat different plumage. The Svalbard population belongs to the light-bellied sub-species B. b. hrota. The brent goose is somewhat smaller than the barnacle goose. The sexes are identical. Adult birds are 55-60 cm long and weigh 1.3-1.6 kg. They have a black head, neck and breast, with white patches on the sides of the neck. The upper-parts of the body and the wings are dark grey-brown; the under-parts are light grey-brown in B. b. hrota (but dark brown in the dark-bellied subspecies B. b. bernicla). The bill and legs are black. Juveniles resemble the adults, though they lack the white neck patches and they have more mottled plumage. Brent geese normally do not fly in the typical V-formation used by other geese, but in irregular masses or lines. Their call is a growling “rruk”.
Brent geese have a holarctic distribution. Light-bellied brent geese nest in northeast Canada, northeast Greenland, Svalbard and Franz Josef Land, while the dark-bellied sub-species nests in the tundra of Siberia east to Taymyr in Russia. East of Taymyr and in the north-western parts of arctic North America, a third sub-species is found, B. b. nigricans. Birds from the Kile area in northeast Greenland aggregate with birds from Svalbard and Franz Josef Land to winter in Denmark and in Northumberland in England. The individuals from the rest of Greenland spend the winter in Ireland, while the dark-bellied sub-species from western Siberia winters along the North Sea coasts from Denmark to southern England and western France. Most of the brent geese in Svalbard breed on Tusenøyane, south of Edgeøya. Some pairs also breed on small islands along the western and northern coast of Spitsbergen -Moffen in the north being the most important of these islands. A few pairs also breed along the coast of Spitsbergen. Brent geese arrive at their nesting sites toward the end of May or in early June. The autumn migration occurs in the first half of September.
Relatively little is known about the biology of this species in Svalbard. They nest on flat tundra areas near ponds and lakes and on islands. During migration and in the winter areas brent geese are more strongly associated with the coast than the other Svalbard geese and they often spend time in delta areas or in shallow-water marine areas. In the breeding season the brent geese in Svalbard feed on various land plants such as scurvy-grass (Cochlearia) and mosses, though they will also feed on various algae in sea-water. During the winter months eelgrass and algae are their main diet. Polar bears, arctic foxes, glaucous gulls and arctic skuas all take eggs and chicks of the brent goose in Svalbard.
Life history and reproduction
Brent geese nest in single pairs or in loose colonies. In Svalbard there appears to be competition with the more dominant barnacle goose for nesting sites. The nest is a shallow depression, usually placed on an elevation in the terrain; the nest is lined with plant material and down. Egg laying usually occurs in mid-June. The three to five eggs are yellow-white and are incubated by the female for 24-26 days. The male remains close to the nest at all times. The nest is abandoned soon after the chicks hatch and the young are fledged after about six weeks. Right around the time of the young fledge the adults moult their plumage leaving them flightless for several weeks. In this period they are very timid and highly sensitive to disturbance. Similar to the other species of geese in Svalbard the parents stay with their young through winter and until the spring migration the following year. Sexual maturity is reached at two or three years of age.
Management status and monitoring
The Svalbard population of the light-bellied brent goose is the smallest discrete migratory goose population in the world. Annual counts in their wintering areas in Denmark and England estimate that the total wintering population in this region in the beginning of the year 2000 numbered 5000-6000 individuals. Exactly what proportion of these birds breed in Svalbard is not clear. Historically, the brent goose was probably the most numerous goose species in Svalbard. It was thought to number in excess of 50,000 individuals. It was widely distributed on islands all along the west coast of Spitsbergen, as well as along the coasts of the rest of the archipelago. The population declined dramatically during the first part of the 20th century, probably due to intensive harvest of down and eggs in the breeding areas, as well as a lack of their staple food – eelgrass Zostera spp. – at their wintering grounds.
(Thanks to Healthy Life Essex for the following information)
How many are there?
About 300,000 worldwide, of which 100,000 come to the UK. 10,000 are found in the Thames Estuary (up to 4000 in Leigh), 7,000 in the Blackwater Estuary and 3,700 in the Couch/Roach Estuary. These three sites are recognised as sites of international importance to the dark-bellied brent goose.
Numbers fluctuate naturally, and are determined largely by Arctic fox and snowy owl predation during the breeding season. If lemmings have an unsuccessful breeding season, these predators turn to brent goose chicks as an easy food source. Brent goose numbers in South Essex have declined steadily for the last 15 years.
Where do they come from?
Brent geese are the most northerly breeding geese in the world. Each year they make a dangerous journey across frozen land and stormy seas to spend the winter around our coast. The Leigh brent geese come from Siberia, northern Russia, over 2,500 miles away and hundreds of miles within the Arctic Circle. Their favourite summer habitat is boggy Arctic tundra with shallow pools, usually near to the sea. They spend winter in estuaries and shallow coasts with mudflats, also grazing on fields near the coast.
When do they come and go?
Brent geese leave their breeding grounds in mid-September, with most arriving in late October to early November. Numbers peak in January. They begin to depart in late February. They stop off along the Baltic coast before reaching the Arctic in early June, just as the snow and ice is beginning to thaw. At night, the geese leave land sites and rest on mudflats to avoid predators.
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. 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).