Swan Goose
Encyclopedia
The Swan Goose is a rare large goose
with a natural breeding range in inland Mongolia
, northernmost China
, and southeastern Russia
. It is migratory
and winters mainly in central and eastern China. Vagrant birds are encountered in Japan
and Korea
(where it used to winter in numbers when it was more common), and more rarely in Kazakhstan
, Laos
, coastal Siberia
, Taiwan
, Thailand
and Uzbekistan
.
This species
has been domesticated. Introduced and feral
populations of its domestic breeds occur in many places outside its natural range. The wild form is also kept in collections, and escapes are not unusual amongst feral flocks of other Anser and Branta
geese.
, wild birds being 81 – long (the longest Anser goose) and weighing 2.8 – or more (the second-heaviest Anser, after the Greylag Goose
A. anser). The sexes are similar, although the male is larger, with a proportionally longer bill and neck; in fact the largest females are barely as large as the smallest males. Typical measurements of the wing are 45 – in males, 37.5 – in females; the bill is about 8.7 – long in males and 7.5 – in females. The tarsus
of males measures around 8.1 cm (3.2 in). The wingspan of adult geese is 160–185 cm (63–72.8 in).
The upperparts are greyish-brown, with thin light fringes to the larger feathers and a maroon hindneck and cap (reaching just below the eye). The remiges are blackish, as are the entire underwing and the white-tipped rectrices, while the upper- and undertail coverts are white. A thin white stripe surrounds the bill base. Apart from darker streaks on the belly and flanks, the underside is pale buff, being especially light on the lower head and foreneck which are sharply delimited against the maroon. In flight, the wings appear dark, with no conspicuous pattern. Uniquely among its genus
, the long, heavy bill is completely black; the legs and feet, on the other hand, are orange as in most of its relatives. The eyes' irides are maroon. Juveniles are duller than adult birds, and lack the white bill base and dark streaks on the underside.
The voice is a loud drawn-out and ascending honking aang. As a warning call, a similar but more barking honk is given two or three times in short succession.
The karyotype
of the Swan Goose is 2n=80, consisting of four pairs of macrochromosomes, 35 pairs of microchromosome
s, and a pair of sex chromosomes. The two largest macrochromosome pairs as well as the Z (female) chromosome are submetacentric, while the third-largest chromosome
pair is acrocentric and the fourth-largest is metacentric. The W chromosomes are acrocentric too, as are the larger microchromosomes, the smaller ones probably being telocentric. Compared to the Greylag Goose, there seems to have been some rearrangement on the fourth-largest chromosome pair.
to taiga
and mountain valleys near freshwater
, grazing on plants such as sedge
s (Cyperaceae), and rarely swimming. It forms small flocks outside the breeding season. In the winter, it grazes on plains and stubble fields, sometimes far from water. Birds return from the winter quarters around April, and the breeding season starts soon thereafter. It breeds as single pairs or loose groups near marshes and other wetland
s, with nesting activity starting about May. The clutch
is usually 5–6 but sometimes up to 8 egg
s, which are laid in a shallow nest made from plants, placed directly on the ground, often on a small knoll
to keep it dry. The precocial
young hatch after about 28 days and become sexually mature at 2–3 years of age. Around late August/early September, the birds leave for winter quarters, where they gather in small groups to moult
their worn plumage.
The Swan Goose was uplisted from Near Threatened
to Vulnerable
in 1992 and further to Endangered in 2000, as its population is declining due to habitat loss and excessive hunting and (particularly on the Sanjiang Plain in China
) egg collecting. But new research has shown it to be not as rare as it was believed, and consequently, it was downlisted to Vulnerable status again in 2008. Still, less than 500 pairs might remain in Russia
, while in Mongolia
numbers are unknown though about 1,000 were seen at Ögii Nuur
in 1977. Favorite wintering locations in China are Lake Dongting, Lake Poyang
, the Yancheng Coastal Wetlands
and other locations around the lower Yangtze River
, where some 60,000 individuals may be found each year – though this may be almost the entire world population. Until the 1950s
, the species wintered in small numbers (up to about 100 birds annually) in Japan
, but habitat destruction
has driven them away. Altogether, between 60,000 and 100,000 adult Swan Geese remain in the wild today.
(A. anser), two breeds are direct descendants of the Swan Goose: the Chinese Goose
and the African Goose
. These breeds have been domesticated since at least the mid-eighteenth century – perhaps even (in China
) since around 1000 BC. They vary considerably from their wild parent in appearance, temperament, and ability to produce meat and eggs; the most conspicuous feature is the prominent bill knob.
Charles Darwin
studied goose breeds as part of his work on the theory of evolution
. He noted that the external differences between Chinese geese and breeds descended from the Greylag Goose belied a rather close relationship:
Goose
The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....
with a natural breeding range in inland Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
, northernmost China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, and southeastern Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. It is migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
and winters mainly in central and eastern China. Vagrant birds are encountered in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
and Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
(where it used to winter in numbers when it was more common), and more rarely in Kazakhstan
Kazakhstan
Kazakhstan , officially the Republic of Kazakhstan, is a transcontinental country in Central Asia and Eastern Europe. Ranked as the ninth largest country in the world, it is also the world's largest landlocked country; its territory of is greater than Western Europe...
, Laos
Laos
Laos Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ Sathalanalat Paxathipatai Paxaxon Lao, officially the Lao People's Democratic Republic, is a landlocked country in Southeast Asia, bordered by Burma and China to the northwest, Vietnam to the east, Cambodia to the south and Thailand to the west...
, coastal Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
, Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
, Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
and Uzbekistan
Uzbekistan
Uzbekistan , officially the Republic of Uzbekistan is a doubly landlocked country in Central Asia and one of the six independent Turkic states. It shares borders with Kazakhstan to the west and to the north, Kyrgyzstan and Tajikistan to the east, and Afghanistan and Turkmenistan to the south....
.
This species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
has been domesticated. Introduced and feral
Feral
A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer. The introduction of feral animals or plants to their non-native regions, like any introduced species, may...
populations of its domestic breeds occur in many places outside its natural range. The wild form is also kept in collections, and escapes are not unusual amongst feral flocks of other Anser and Branta
Branta
The black geese of the genus Branta are waterfowl belonging to the true geese and swans subfamily Anserinae. They occur in the northern coastal regions of the Palearctic and all over North America, migrating to more southernly coasts in winter, and as resident birds in the Hawaiian Islands...
geese.
Description
The Swan Goose is large and long-necked for its genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, wild birds being 81 – long (the longest Anser goose) and weighing 2.8 – or more (the second-heaviest Anser, after the Greylag Goose
Greylag Goose
The Greylag Goose , Anser anser, is a bird with a wide range in the Old World. It is the type species of the genus Anser....
A. anser). The sexes are similar, although the male is larger, with a proportionally longer bill and neck; in fact the largest females are barely as large as the smallest males. Typical measurements of the wing are 45 – in males, 37.5 – in females; the bill is about 8.7 – long in males and 7.5 – in females. The tarsus
Tarsus (skeleton)
In tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...
of males measures around 8.1 cm (3.2 in). The wingspan of adult geese is 160–185 cm (63–72.8 in).
The upperparts are greyish-brown, with thin light fringes to the larger feathers and a maroon hindneck and cap (reaching just below the eye). The remiges are blackish, as are the entire underwing and the white-tipped rectrices, while the upper- and undertail coverts are white. A thin white stripe surrounds the bill base. Apart from darker streaks on the belly and flanks, the underside is pale buff, being especially light on the lower head and foreneck which are sharply delimited against the maroon. In flight, the wings appear dark, with no conspicuous pattern. Uniquely among its genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
, the long, heavy bill is completely black; the legs and feet, on the other hand, are orange as in most of its relatives. The eyes' irides are maroon. Juveniles are duller than adult birds, and lack the white bill base and dark streaks on the underside.
The voice is a loud drawn-out and ascending honking aang. As a warning call, a similar but more barking honk is given two or three times in short succession.
The karyotype
Karyotype
A karyotype is the number and appearance of chromosomes in the nucleus of an eukaryotic cell. The term is also used for the complete set of chromosomes in a species, or an individual organism.p28...
of the Swan Goose is 2n=80, consisting of four pairs of macrochromosomes, 35 pairs of microchromosome
Microchromosome
A microchromosome is a type of very small chromosome which is a typical component of the karyotype of birds, some reptiles, fish, and amphibians; they tend to be absent in mammals. They are less than 20 Mb in size; chromosomes which are greater than 40 Mb in size are known as macrochromosomes,...
s, and a pair of sex chromosomes. The two largest macrochromosome pairs as well as the Z (female) chromosome are submetacentric, while the third-largest chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
pair is acrocentric and the fourth-largest is metacentric. The W chromosomes are acrocentric too, as are the larger microchromosomes, the smaller ones probably being telocentric. Compared to the Greylag Goose, there seems to have been some rearrangement on the fourth-largest chromosome pair.
Ecology
It inhabits steppeSteppe
In physical geography, steppe is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas, and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes...
to taiga
Taiga
Taiga , also known as the boreal forest, is a biome characterized by coniferous forests.Taiga is the world's largest terrestrial biome. In North America it covers most of inland Canada and Alaska as well as parts of the extreme northern continental United States and is known as the Northwoods...
and mountain valleys near freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
, grazing on plants such as sedge
Cyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...
s (Cyperaceae), and rarely swimming. It forms small flocks outside the breeding season. In the winter, it grazes on plains and stubble fields, sometimes far from water. Birds return from the winter quarters around April, and the breeding season starts soon thereafter. It breeds as single pairs or loose groups near marshes and other wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
s, with nesting activity starting about May. The clutch
Clutch (eggs)
A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...
is usually 5–6 but sometimes up to 8 egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
s, which are laid in a shallow nest made from plants, placed directly on the ground, often on a small knoll
Hillock
A hillock or knoll is a small hill, usually separated from a larger group of hills such as a range. Hillocks are similar in their distribution and size to small mesas or buttes. The term is largely a British one...
to keep it dry. The precocial
Precocial
In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born or hatched helpless. Extremely precocial species may be called...
young hatch after about 28 days and become sexually mature at 2–3 years of age. Around late August/early September, the birds leave for winter quarters, where they gather in small groups to moult
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...
their worn plumage.
The Swan Goose was uplisted from Near Threatened
Near Threatened
Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...
to Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
in 1992 and further to Endangered in 2000, as its population is declining due to habitat loss and excessive hunting and (particularly on the Sanjiang Plain in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
) egg collecting. But new research has shown it to be not as rare as it was believed, and consequently, it was downlisted to Vulnerable status again in 2008. Still, less than 500 pairs might remain in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, while in Mongolia
Mongolia
Mongolia is a landlocked country in East and Central Asia. It is bordered by Russia to the north and China to the south, east and west. Although Mongolia does not share a border with Kazakhstan, its western-most point is only from Kazakhstan's eastern tip. Ulan Bator, the capital and largest...
numbers are unknown though about 1,000 were seen at Ögii Nuur
Ögii Nuur
Ögii Nuur may refer to* Ögii Lake , in Mongolia* Ögii Nuur District, in Mongolia...
in 1977. Favorite wintering locations in China are Lake Dongting, Lake Poyang
Lake Poyang
Poyang Lake , located in Jiangxi Province is the largest freshwater lake in China.It has a surface area of 3,585 km², a volume of 25 km³ and an average depth of eight meters. The lake provides a habitat for half a million migratory birds, and is a favorite destination for birding...
, the Yancheng Coastal Wetlands
Yancheng Coastal Wetlands
The Yancheng Coastal Wetlands refers to the wetlands in Yancheng, Jiangsu province, China.It is named after the Dongbei and Liao Rivers is connected to the Songnen Plain through the Yellow River Valley; a small plain lies north of Dongting Lake in the west....
and other locations around the lower Yangtze River
Yangtze River
The Yangtze, Yangzi or Cháng Jiāng is the longest river in Asia, and the third-longest in the world. It flows for from the glaciers on the Tibetan Plateau in Qinghai eastward across southwest, central and eastern China before emptying into the East China Sea at Shanghai. It is also one of the...
, where some 60,000 individuals may be found each year – though this may be almost the entire world population. Until the 1950s
1950s
The 1950s or The Fifties was the decade that began on January 1, 1950 and ended on December 31, 1959. The decade was the sixth decade of the 20th century...
, the species wintered in small numbers (up to about 100 birds annually) in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, but habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
has driven them away. Altogether, between 60,000 and 100,000 adult Swan Geese remain in the wild today.
Domestication
Though the majority of domestic geese are descended from the Greylag GooseGreylag Goose
The Greylag Goose , Anser anser, is a bird with a wide range in the Old World. It is the type species of the genus Anser....
(A. anser), two breeds are direct descendants of the Swan Goose: the Chinese Goose
Chinese goose
The Chinese Goose is a breed of domesticated goose descended from the wild Swan Goose. Chinese geese differ from the wild birds in much larger size , and in having an often strongly developed basal knob on the upper side of the bill. The knob at the top of the beak is more prominent on males than...
and the African Goose
African goose
The African is a breed of domestic goose. Not actually African at all, African breed geese are descended from the wild Swan Goose, just like their close cousin the Chinese goose. Though they share some similar characteristics , the two can be distinguished by the African's larger dewlap and...
. These breeds have been domesticated since at least the mid-eighteenth century – perhaps even (in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
) since around 1000 BC. They vary considerably from their wild parent in appearance, temperament, and ability to produce meat and eggs; the most conspicuous feature is the prominent bill knob.
Charles Darwin
Charles Darwin
Charles Robert Darwin FRS was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.He published his theory...
studied goose breeds as part of his work on the theory of evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
. He noted that the external differences between Chinese geese and breeds descended from the Greylag Goose belied a rather close relationship:
"The hybrids from the common and Chinese geese (A. cygnoides), species which are so different that they are generally ranked in distinct genera, have often bred in this country with either pure parent, and in one single instance they have bred inter se."