Greater white fronted goose (Anser albifrons albifrons)

Описание: Greater white-fronted goose
Anser albifrons
Kolgans / Bläßgans / Oie rieuse

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence over 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 (over 30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (over 10,000 mature individuals with a continuing decline estimated to be over 10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern (IUCN, 2012).

This species is fully migratory (del Hoyo et al. 1992), travelling in stages via several stop-over sites between separate breeding and wintering grounds (Madge and Burn 1988). The species breeds from late-May or early-June in single pairs or loose groups (del Hoyo et al. 1992), with moulting non-breeders and failed breeders gathering on areas of open water separate from the major breeding congregations (Kear 2005a). After breeding the species gathers in small flocks (less than 30 individuals) (Scott and Rose 1996) to undergo a post-breeding moult period (Madge and Burn 1988) near the breeding grounds where it becomes flightless for c.25 days (Scott and Rose 1996). After this moulting period flocks gather to migrate south to winter quarters, leaving the breeding areas from late-August through September and arriving late in the autumn (Madge and Burn 1988). Outside of the breeding season the species is highly gregarious (Madge and Burn 1988) (large flocks of up to 30,000 individuals are recorded in Europe) although it is more commonly observed in small loose groups due to the patchiness of its favoured habitat (Kear 2005a). The species usually forages within 20 km of rooting sites (Kear 2005a), although the optimum distance for foraging areas may be less than this (less than 4 km in Scotland, UK) (Vickery and Gill 1999).

The species breeds in open (del Hoyo et al. 1992), low-lying, shrubby tundra (Snow and Perrins 1998) on the coast and inland (del Hoyo et al. 1992), in close proximity to marshes, lakes, pools, rivers (del Hoyo et al. 1992, Snow and Perrins 1998), and willow- and shrub-lined ponds and streams (Johnsgard 1978). It requires dry slopes, banks, mounds, hummocks or patches of sand or clay for nesting sites, especially those commanding good views of the surrounding area (Snow and Perrins 1998). Non-breeding The species winters in open country on steppe and agricultural land (del Hoyo et al. 1992) (e.g. improved grassland, stubble fields (Madge and Burn 1988) and wet meadows (Johnsgard 1978)), or in brackish (Kear 2005a) and freshwater marshy habitats (del Hoyo et al. 1992) (such as upland bogs (Madge and Burn 1988), peatlands (Scott and Rose 1996) and floodlands (Kear 2005a)). It may also roost on tidal marshes, in sheltered bays or in estuaries and frequents inland lakes and reservoirs in North America (Kear 2005a).

The species is herbivorous, its diet consisting of the roots, leaves, stems, seeds and fruits of terrestrial plants such as herbs, grasses and sedges (del Hoyo et al. 1992), as well as agricultural grain (e.g. corn, oats (del Hoyo et al. 1992), wheat, rice and barley (Johnsgard 1978)), potatoes and sprouting cereals (especially in the winter) (del Hoyo et al. 1992).

The nest is a shallow construction of plant matter on the ground (del Hoyo et al. 1992) amongst vegetation such as grass or dwarf scrub heath, often on raised hummocks or slopes to reduce the risk of flooding and provide a vantage point of the surrounding area (Kear 2005a).

An investigation carried out in one of the species's wintering areas (UK) found that it was most likely to forage on grasslands managed with a livestock (cattle) grazing regime, with a sward height of 13-20 cm, at a distance of less than 9 km away from roosting sites (the optimum distance was 4 km away) (Vickery and Gill 1999). Fertilising the grassland with nitrogen in the autumn (mid-October) at a rate of 125 kg N ha1 was also found to increase the overall species use of the habitat by 42 % compared with unfertilised areas (Vickery and Gill 1999).

More info: https://harteman.nl/anseralbifrons