Barnacle geese migrate very large distances very quickly. However the fantastic group of 44 that I saw at the Gravel Pits today were certainly feral and non-migratory - although that itself raises a number of questions! Why is the migratory pattern so strong and consistent in wild birds - and how do feral birds "lose" this tendency?
As a species that is increasing its feral population worldwide as well as undergoing significant expansion and establishing new breeding areas in the wild (in the Baltic increasing from zero to over 17,000 birds in 27 years) it is noteworthy that there is a new Dutch breeding population over 4,000 birds already, apparently also non-migratory (???).
In nature barnacle geese don't exercise particularly more to practice flying in the periods before migrations of thousands of miles at a time. However they do spontaneously increase muscle mass (how?) and may undergo a number of other physiological changes before setting off. Their heavier mass itself may mean that they have to work harder in these periods.
Wild birds tend to trial pair in their first year or two, but then pair more or less for life. They tend to migrate in family groups, and sisters of the same year group tend to nest close to each other, while males tend to disperse a bit more. Do they break out from the family migration groups?
The Greenland birds winter in Ireland and Western Scotland, especially the Hebrides, the Svalbard birds winter in the Solway/Southern Scotland area, while the Novaya Zembla birds (and the newer Faroes population) winter mainly in the Netherlands. The last population is bigger than the other two together.
In the Solway population, the birds always arrive in Caerlaverock and then depart from Rockcliffe, both areas of which are traditional over-wintering grounds. They also now use two further areas around the Solway, in Southerness and in Morecambe Bay, as numbers increase. To indicate the scale of this over-wintering, numbers dropped to about 400 in the 40s, apparently due to disturbance, but are now up to about 25,000, with very significant support!
Populations in the Netherlands are also on the increase, due again to nature conservation measures, although West Germany in contrast has lost most (all?) of its original over-wintering habitat. The increase in over-wintering numbers presumably increases numbers/density on the breeding grounds, potentially having multiple effects on the Artic ecology. Increasing pink-footed goose numbers may increase grubbing and digging, affecting soil temperature and type and amount of plant regrowth, thus possibly affecting barnacle goose and other herbivore numbers indirectly as well as directly. The barnacle geese may however be able to compete relatively better on the short grass swards around the nests, so its not all a one-way street.
The increase in winter protection and feeding opportunities is likely then to be partly responsible for increased populations on the breeding grounds, which may impact on the artic ecosystems primarily via effects on the artic flora and ecosystem functioning. The Svalbard population used to be mainly confined to islands to avoid predation, but has now "spilt over" to mainland cliff sites, presumably less than ideal from the goose's point of view. As the bird is relatively small it is more subject to artic fox predation than other goose species, which are able to breed more freely on the valley bottoms and repel the foxes. Foxes are a major predator, but gulls are mentioned in Russia, and Polar bears, skuas and eagles may also be involved.
It may share breeding grounds with other species such as the pink-footed goose, but at least on the mainlands the barnacle nests on the steepest ground, and needs watery refuges against predation following hatching, while the pink-footed goose is more free to nest and feed on better vegetated areas. As a smaller goose the barnacle is also less able to dig up plant parts such as rhizomes, at any time in the breeding cycle, thus leading to at least some partitioning in resources.
Branta leucopsis is present on its breeding grounds from May or June to August or September where it breeds in small but often closely packed colonies of 5-50 pairs, occasionally singly or in groups of up to 150 pairs. It uses the same nesting sites year after year and sometimes nests among seabird colonies. The females incubate and must not wander too far from the nest to avoid egg predation. They must use a large amount of energy up, and may use all their food items immediately around their nests.
After the young hatch the adults undergo a flightless moult period near the breeding grounds between mid-July and mid-August that lasts for 3-4 weeks. The species then migrates to autumn staging areas in September from which it travels via regular stop-over sites to the wintering grounds, arriving in late-September (??) The Svalbard birds may fly generally fairly directly (?). The return migration begins in April or May, the species moving to spring staging areas where it may be present for 20-30 days before migrating northwards. This spring stop is generally more important because (at least) the females have to have reserves to go virtually into non-feeding incubating mode as soon as the snow melts and nesting can begin (this is of course a fine judgement, dependent upon that year's weather conditions). Such careful judgements may benefit from the social structure and group migration strategy being (generally?) used, ensuring the benefit of experience from the older birds is used.
The species is highly gregarious outside of the breeding season, often feeding in dense concentrations on coastal grasslands during the winter. In winter habitats it roosts on water or on sandbanks near saltmarshes and pastureland.
The species is herbivorous, on the winter grounds apparently preferring well fertilised grass that perhaps has been cut for silage and then grazed, on medium to large sized fields (4 - 10 hectares). Upon landing the group is tight and easily spooked for the first ten minutes at least but may then relax. Larger groups may tend to spread out a bit more to reduce competition for food. The geese may graze cyclically, encouraging a grass regeneration of young plants with a high protein concentration.
Feral groups appear to move about quite a lot in winter presumably consisting of individuals having escaped from collections, with perhaps some resulting offspring. A new small population of Icelandic breeding birds are said to have possibly developed from escapes.
As a species that is increasing its feral population worldwide as well as undergoing significant expansion and establishing new breeding areas in the wild (in the Baltic increasing from zero to over 17,000 birds in 27 years) it is noteworthy that there is a new Dutch breeding population over 4,000 birds already, apparently also non-migratory (???).
In nature barnacle geese don't exercise particularly more to practice flying in the periods before migrations of thousands of miles at a time. However they do spontaneously increase muscle mass (how?) and may undergo a number of other physiological changes before setting off. Their heavier mass itself may mean that they have to work harder in these periods.
Wild birds tend to trial pair in their first year or two, but then pair more or less for life. They tend to migrate in family groups, and sisters of the same year group tend to nest close to each other, while males tend to disperse a bit more. Do they break out from the family migration groups?
The Greenland birds winter in Ireland and Western Scotland, especially the Hebrides, the Svalbard birds winter in the Solway/Southern Scotland area, while the Novaya Zembla birds (and the newer Faroes population) winter mainly in the Netherlands. The last population is bigger than the other two together.
In the Solway population, the birds always arrive in Caerlaverock and then depart from Rockcliffe, both areas of which are traditional over-wintering grounds. They also now use two further areas around the Solway, in Southerness and in Morecambe Bay, as numbers increase. To indicate the scale of this over-wintering, numbers dropped to about 400 in the 40s, apparently due to disturbance, but are now up to about 25,000, with very significant support!
Populations in the Netherlands are also on the increase, due again to nature conservation measures, although West Germany in contrast has lost most (all?) of its original over-wintering habitat. The increase in over-wintering numbers presumably increases numbers/density on the breeding grounds, potentially having multiple effects on the Artic ecology. Increasing pink-footed goose numbers may increase grubbing and digging, affecting soil temperature and type and amount of plant regrowth, thus possibly affecting barnacle goose and other herbivore numbers indirectly as well as directly. The barnacle geese may however be able to compete relatively better on the short grass swards around the nests, so its not all a one-way street.
The increase in winter protection and feeding opportunities is likely then to be partly responsible for increased populations on the breeding grounds, which may impact on the artic ecosystems primarily via effects on the artic flora and ecosystem functioning. The Svalbard population used to be mainly confined to islands to avoid predation, but has now "spilt over" to mainland cliff sites, presumably less than ideal from the goose's point of view. As the bird is relatively small it is more subject to artic fox predation than other goose species, which are able to breed more freely on the valley bottoms and repel the foxes. Foxes are a major predator, but gulls are mentioned in Russia, and Polar bears, skuas and eagles may also be involved.
It may share breeding grounds with other species such as the pink-footed goose, but at least on the mainlands the barnacle nests on the steepest ground, and needs watery refuges against predation following hatching, while the pink-footed goose is more free to nest and feed on better vegetated areas. As a smaller goose the barnacle is also less able to dig up plant parts such as rhizomes, at any time in the breeding cycle, thus leading to at least some partitioning in resources.
Branta leucopsis is present on its breeding grounds from May or June to August or September where it breeds in small but often closely packed colonies of 5-50 pairs, occasionally singly or in groups of up to 150 pairs. It uses the same nesting sites year after year and sometimes nests among seabird colonies. The females incubate and must not wander too far from the nest to avoid egg predation. They must use a large amount of energy up, and may use all their food items immediately around their nests.
After the young hatch the adults undergo a flightless moult period near the breeding grounds between mid-July and mid-August that lasts for 3-4 weeks. The species then migrates to autumn staging areas in September from which it travels via regular stop-over sites to the wintering grounds, arriving in late-September (??) The Svalbard birds may fly generally fairly directly (?). The return migration begins in April or May, the species moving to spring staging areas where it may be present for 20-30 days before migrating northwards. This spring stop is generally more important because (at least) the females have to have reserves to go virtually into non-feeding incubating mode as soon as the snow melts and nesting can begin (this is of course a fine judgement, dependent upon that year's weather conditions). Such careful judgements may benefit from the social structure and group migration strategy being (generally?) used, ensuring the benefit of experience from the older birds is used.
The species is highly gregarious outside of the breeding season, often feeding in dense concentrations on coastal grasslands during the winter. In winter habitats it roosts on water or on sandbanks near saltmarshes and pastureland.
The species is herbivorous, on the winter grounds apparently preferring well fertilised grass that perhaps has been cut for silage and then grazed, on medium to large sized fields (4 - 10 hectares). Upon landing the group is tight and easily spooked for the first ten minutes at least but may then relax. Larger groups may tend to spread out a bit more to reduce competition for food. The geese may graze cyclically, encouraging a grass regeneration of young plants with a high protein concentration.
Feral groups appear to move about quite a lot in winter presumably consisting of individuals having escaped from collections, with perhaps some resulting offspring. A new small population of Icelandic breeding birds are said to have possibly developed from escapes.
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