Ross's goose

Chen rossii

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Genus: Chen
Specie: Chen rossii
Conservation status:
The Ross's goose is a North American species of goose.

The American Ornithologists' Union places this species and the other two "white" geese in the genus Chen rather than the more traditional "grey" goose genus Anser.

This goose breeds in northern Canada, mainly in the Queen Maud Gulf Migratory Bird Sanctuary, and winters much further south in the continent in the southern United States and occasionally northern Mexico.
The plumage of this species is white except for black wing tips. It is similar in appearance to a white-phase snow goose but approximately 40% smaller. Other differences from the snow goose are that the bill is smaller in proportion to its body and lacks "black lips". The dark phase is extremely rare.

The Ross's goose is a rare vagrant to Western Europe, but it is commonly kept in wildfowl collections and so the true frequency of wild birds is hard to ascertain. Escaped or feral specimens are encountered frequently, usually in the company of other feral geese such as Canada goose, greylag goose and barnacle goose. However, individuals or small groups that seemed to be of natural origin have turned up in the Netherlands and Britain.

This species is named in honor of Bernard R. Ross, a Hudson's Bay Company factor at Fort Resolution in Canada's Northwest Territories.
The breeding range of Ross’s goose spreads throughout the Canadian Arctic. In winter, flocks mostly migrate to California, although congregations can also be found in Texas and northern Mexico. The range of this species is thought to be spreading east. There have been reports of vagrant Ross’s geese in the Netherlands.
During the breeding season Ross’s goose is found in Arctic tundra, where it nests in open areas and on islands in shallow lakes. In winter, large aggregations are found in agricultural fields and shallow wetlands, using nearby reservoirs and lakes to roost.
Ross’s goose has an herbivorous diet, which consists of roots, leaves, stems, sedges, legumes and domestic grains. This species can be seen foraging on the ground individually, or may form larger groups.

A migratory species, Ross’s goose leaves its breeding ground in mid-October and arrives in its overwintering r ange in late October. Flocks begin to return to the breeding grounds in early March. While migrating, this species is highly gregarious and forms large flocks.

Between late May and June mated pairs arrive at the breeding grounds and immediately establish a nesting territory. Although Ross’s goose is thought to be monogamous, copulation with other individuals outside of the pair is also known to occur. The female builds the nest during and after the territory establishment. The nest is a shallow structure, with twigs, grass, moss and lichens in the outer layer and mostly down on the inner layer. The female lays an average clutch of between 4 and 5 eggs at the beginning of June, which are laid at 36-hour intervals. The female incubates the eggs, while being guarded by the male, and the eggs hatch between late June and July. If the female leaves the nest, it will cover the eggs with a layer of down to keep the eggs warm and hide them from predators. The young are able to leave the nest 24 hours after hatching, and can swim and feed themselves. For up to a year after birth, the young maintain an association with the adults and may remain with them until the next breeding season. Ross’s goose reaches sexual maturity after 2 or 3 years, and lives for up to 14 years in the wild.
Most migration occurs through northwest and west-central Montana. Single or small groups of Ross's geese often migrate with Snow Geese. About 20,000 to 40,000 stop at Freezeout Lake Wildlife Management Area each spring and fall; this is approximately 20% of the total world population (Schwitters, personal communication).
Historically, Ross’s goose was threatened by hunting in its winter range, and this market drastically reduced wild populations and may have threatened this species with extinction. Hunting became illegal in 1931 and the population has dramatically increased since, causing North American authorities to change the law and allow hunting to resume, with the aim of reducing the population size by half.

As it is such an abundant species, there do not seem to be many threats to the future survival of Ross’s goose, although habitat loss, disease and hybridisation with the snow goose (Chen caerulescens) may affect population numbers in the future.

Zoológico de Vallarta A. C.

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