Branta

Red List Category

Red List Criteria

Version

2012

BirdLife International

Butchart, S. & Symes, A.

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Behaviour This species is fully migratory, the main routes of migration being along Arctic coastlines (Snow and Perrins 1998). It arrives on the breeding grounds in early-June (Madge and Burn 1988, Scott and Rose 1996) where it may breed in small, loose colonies (Madge and Burn 1988, del Hoyo et al. 1992, Snow and Perrins 1998) or dispersed in single pairs (Snow and Perrins 1998) (especially in the high Arctic where the habitat is unsuitable for large groups) (Kear 2005a). There is a high degree of synchrony in egg laying and hatching (Johnsgard 1978), with the adults moulting c.10 days after the young hatch (mid-July to mid-August (Scott and Rose 1996)) during which they become flightless for c.21-30 days (Johnsgard 1978, Scott and Rose 1996). Most individuals moult near the breeding grounds (Scott and Rose 1996) although immatures, unsuccessful breeders (Johnsgard 1978) and some more southerly breeding groups (Flint et al. 1984) may undertake pre-moult migrations (Johnsgard 1978) and form large moulting concentrations well-away from nesting areas (Flint et al. 1984). After the post-breeding moult flocks leave the breeding grounds in early-September with some arriving in wintering areas as early as mid-September, others making stopovers on route and arriving later (Madge and Burn 1988). It leaves its wintering quarters again from mid-March to mid-April (Madge and Burn 1988). During the non-breeding season the species remains gregarious, gathering in groups of only a few to several thousands of individuals (Snow and Perrins 1998), although it is rarely found in very large flocks (Kear 2005a). Habitat Breeding The species breeds in coastal Arctic tundra (del Hoyo et al. 1992) in or close to wet coastal meadows with abundant grassy vegetation (Kear 2005a) and on tundra-covered flats with tidal streams (only just above the high tide line) (Johnsgard 1978). In some parts of its range it shows a preference for nesting on small grassy islands (Johnsgard 1978, Madge and Burn 1988, Kear 2005a) in tundra lakes and rivers, especially if nesting Sabine's Gulls Xema sabini (Kear 2005a), Snowy Owls Bubo scandiaca (Flint et al. 1984, Kear 2005a), Peregrine Falcons Falco peregrinus (Flint et al. 1984) or large raptors are present to deter predators (Kear 2005a). High Arctic nesters may also breed widely dispersed over icy tundra, well-away from water (Kear 2005a). Non-breeding Outside of the breeding season the species becomes predominantly coastal, inhabiting estuaries (del Hoyo et al. 1992, Kear 2005a), tidal mudlflats (Madge and Burn 1988, Kear 2005a), sandy shores (del Hoyo et al. 1992), coastal saltmarshes (Kear 2005a) (especially in the spring) (Scott and Rose 1996) and shallow muddy bays (Kear 2005a). In recent years the species has taken to grazing on coastal cultivated grasslands (Madge and Burn 1988, Scott and Rose 1996) and winter cereal fields (Scott and Rose 1996), but rarely occurs on freshwater wetlands except on passage (Madge and Burn 1988). Diet The species is mainly herbivorous (del Hoyo et al. 1992) although it may take animal matter (e.g. fish eggs, worms, snails and amphipods) (Johnsgard 1978). Breeding In its breeding habitat the diet of the species consists of mosses, lichens, aquatic plants (del Hoyo et al. 1992), sedges, tundra grass Dupontia spp., arrowgrass Triglochin spp. and saltmarsh grass Puccinellia spp. (Alaska) (Kear 2005a), although the young may also take insects and aquatic invertebrates (Johnsgard 1978). Non-breeding Outside of the breeding season the species predominantly takes marine microscopic and macroscopic algae (del Hoyo et al. 1992) (e.g. seaweeds, Ulva spp. (Kear 2005a)) and other aquatic plants linked with saline or brackish waters (del Hoyo et al. 1992) in the intertidal zone (e.g. especially eelgrass Zostera spp. (Madge and Burn 1988, Kear 2005a), as well as Ruppia maritima, Spartina alterniflora, Salicornia spp., and arrowgrass Triglochin spp.) (Kear 2005a). Breeding site The nest is a shallow depression (Flint et al. 1984, del Hoyo et al. 1992) on the ground (del Hoyo et al. 1992). Although the species often nests close to water (del Hoyo et al. 1992) typically within a few hundred metres of the tideline (Snow and Perrins 1998), high Arctic nesters may breed on icy tundra well away from water (Kear 2005a) (some nearly up to 10 km inland) (Snow and Perrins 1998) often near boulders where the snow clears first (Kear 2005a). Management information An investigation carried out in one of the species's wintering areas (UK) found that it was most likely to forage on dry, improved grasslands that had high abundances of the grass Lolium perenne, were between 5 and 6 ha in area, and were at a distance of up to 1.5 km inland or 4-5 km along the coast from coastal roosting sites (Vickery and Gill 1999). The species was found to show a preference for grasslands with short, dense swards c.5 cm in height, a characteristic that can be gained through summer management plans involving either mechanical cutting, livestock (sheep or cattle) grazing regimes, or cutting and then grazing (although over longer periods of time the selective grazing of sheep rather than cattle, and frequent rather than infrequent cutting may be more likely to enhance tillering and produce the short, dense sward favoured by this species) (Vickery and Gill 1999). Fertilising the grassland with nitrogen in the autumn at a rate of 50 kg N ha¹ was found to increase the overall species use of the habitat by 21 % compared with unfertilised areas (Vickery and Gill 1999), and fertilising at a rate of 75 kg N ha¹ was found to increase the overall species use of the habitat by 9-29 % and to remove any preference the geese showed for short sward heights (between 5 and 11 cm) (Vickery and Gill 1999). In other fertilising experiments grazing intensity of the species was found to increase linearly with increasing levels of fertiliser (from 0 kg N ha¹ to 150 kg N ha¹), although responses in grazing intensity at fertiliser levels lower than 50 kg N ha¹ were found to be short-lived (c.2 months after fertiliser application) (Vickery and Gill 1999).