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The tundra swan (''Cygnus columbianus'') is a small
swan Swans are birds of the genus ''Cygnus'' within the family Anatidae. The swans' closest relatives include the goose, geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe (biology) ...
of the
Holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...
. The two
taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
within it are usually regarded as
conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...
, but are also sometimes split into two
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
: Bewick's swan (''Cygnus bewickii'') of the Palaearctic and the whistling swan (''C. columbianus'') proper of the
Nearctic The Nearctic realm is one of the eight biogeographic realms constituting the Earth's land surface. The Nearctic realm covers most of North America, including Greenland, Central Florida, and the highlands of Mexico. The parts of North America ...
. Birds from eastern Russia (roughly east of the Taymyr Peninsula) are sometimes separated as the subspecies ''C. c. jankowskii'', but this is not widely accepted as distinct, with most authors including them in ''C. c. bewickii''. Tundra swans are sometimes separated in the
subgenus In biology, a subgenus ( subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between the ge ...
''Olor'' together with the other
Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...
swan species. Bewick's swan was named in 1830 by William Yarrell after the engraver Thomas Bewick, who specialised in illustrations of birds and animals. ''Cygnus'' is the Latin for "swan", and '' columbianus'' comes from the
Columbia River The Columbia River (Upper Chinook language, Upper Chinook: ' or '; Sahaptin language, Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river headwater ...
, the type locality.


Description

''C. columbianus'' is the smallest of the
Holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical reg ...
swans, at in length, in wingspan and a weight range of . In adult birds, the plumage of both
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
is entirely white, with black feet, and a bill that is mostly black, with a thin salmon-pink streak running along the mouthline and – depending on the subspecies – more or less yellow in the proximal part. The iris is dark brown. In birds living in waters that contains large amounts of iron ions (e.g.
bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and musk ...
lakes), the head and neck plumage acquires a golden or rusty hue. Pens (females) are slightly smaller than cobs (males), but do not differ in appearance otherwise. Immatures of both subspecies are white mixed with some dull grey feathering, mainly on the head and upper neck, which are often entirely light grey; their first-summer plumage is quite white already, and in their second winter they moult into the adult plumage. Their bills are black with a large dirty-pink patch taking up most of the proximal half and often black nostrils, and their feet are dark grey with a pinkish hue. Downy young are silvery grey above and white below. Bewick's swans are the smaller subspecies. There is a slight size
cline Cline may refer to: Science * Cline (biology), a measurable gradient in a single trait in a species across its geographical range * Cline (hydrology), a fluid layer with a property that varies * Cline (mathematics) or generalised circle, a ci ...
, with the eastern birds being slightly larger; good measurement data only exists for the western populations however. These weigh , on average in males and in females. They measure in overall length; each wing is long, on average in males and in females. The tarsus measures in length, the bill , averaging . Bewick's swan is similar in appearance to the parapatric whooper swan (''C. cygnus''), but is smaller, shorter-necked and has a more rounded head shape, with variable bill pattern, but always showing more black than yellow and having a blunt forward edge of the yellow base patch. Whooper swans have a bill that has more yellow than black and the forward edge of the yellow patch is usually pointed. The bill pattern for every individual Bewick's swan is unique, and scientists often make detailed drawings of each bill and assign names to the swans to assist with studying these birds. The eastern birds, apart from being larger, tend towards less yellow on the bill, perhaps indicating that
gene flow In population genetics, gene flow (also known as migration and allele flow) is the transfer of genetic variation, genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent ...
across
Beringia Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 70th parallel north, 72° north latitude in the Chukchi Sea; and on the south ...
, while marginal, never entirely ceased. An apparent case of hybridization between a Bewick's and a vagrant whistling swan has been reported from eastern
Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...
. Whistling swans weigh – on average in males and in females –, and measure in length. Each wing is long; the tarsus measures in length, and the bill is long. ''C. c. columbianus'' is distinguished from ''C. c. bewickii'' by its larger size and the mostly black bill, with just a small and usually hard to see yellow spot of variable size at the base. It is distinguished from the largely
allopatric Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...
trumpeter swan (''C. buccinator'') of North America by that species' much larger size and particularly long bill, which is black all over except for the pink mouthline, which is stronger than in the whistling swan. Note that color variations with more or less yellow, or pink instead of yellow or black, are not exceptional, especially in Bewick's swans, which very rarely may even have yellowish feet. The small size and particularly the rather short neck, which make it look like a large white goose, are still distinguishing marks. Tundra swans have high-pitched honking calls and sound similar to a black goose (''Branta''). They are particularly vocal when foraging in flocks on their wintering grounds; any
conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...
arriving or leaving will elicit a bout of loud excited calling from its fellows. Contrary to its common name, the ground calls of the whistling swan are not a whistle and neither notably different from that of Bewick's swan. The flight call of the latter is a low and soft ringing bark, ''bow-wow...''; the whistling swan gives a markedly high-pitched trisyllabic bark like ''wow-wow-wow'' in flight. By contrast, the whooper and trumpeter swans' names accurately describe their calls—a deep hooting and a higher-pitched
French horn The French horn (since the 1930s known simply as the horn in professional music circles) is a brass instrument made of tubing wrapped into a coil with a flared bell. The double horn in F/B (technically a variety of German horn) is the horn most o ...
-like honk, respectively. Flying birds of these species are shorter-necked and have a quicker wingbeat than their relatives, but they are often impossible to tell apart except by their calls.


Distribution

As their common name implies, the tundra swan breeds in the
tundra In physical geography, a tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: #Arctic, Arctic, Alpine tundra, Alpine, and #Antarctic ...
of the
Arctic The Arctic (; . ) is the polar regions of Earth, polar region of Earth that surrounds the North Pole, lying within the Arctic Circle. The Arctic region, from the IERS Reference Meridian travelling east, consists of parts of northern Norway ( ...
and
subarctic The subarctic zone is a region in the Northern Hemisphere immediately south of the true Arctic, north of hemiboreal regions and covering much of Alaska, Canada, Iceland, the north of Fennoscandia, Northwestern Russia, Siberia, and the Cair ...
, where they inhabit shallow pools, lakes and rivers. These birds, unlike mute swans (''C. olor'') but like the other Arctic swans, are migratory birds. The winter
habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...
of both subspecies is
grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...
and
marsh In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in genera ...
land, often near the coast; they like to visit fields after harvest to feed on discarded grains and while on migration may stop over on mountain lakes. According to ''
National Geographic ''National Geographic'' (formerly ''The National Geographic Magazine'', sometimes branded as ''Nat Geo'') is an American monthly magazine published by National Geographic Partners. The magazine was founded in 1888 as a scholarly journal, nine ...
'', when migrating these birds can fly at altitudes of in a V formation. The breeding range of ''C. c. bewickii'' extends across the coastal lowlands of
Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...
, from the
Kola Peninsula The Kola Peninsula (; ) is a peninsula in the extreme northwest of Russia, and one of the largest peninsulas of Europe. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely inside the Arctic Circle and is border ...
east to the Pacific. They start to arrive on the breeding grounds around mid-May, and leave for winter quarters around the end of September. The populations west of the Taymyr Peninsula migrate via the
White Sea The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the nort ...
,
Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...
and the
estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...
of the
Elbe The Elbe ( ; ; or ''Elv''; Upper Sorbian, Upper and , ) is one of the major rivers of Central Europe. It rises in the Giant Mountains of the northern Czech Republic before traversing much of Bohemia (western half of the Czech Republic), then Ge ...
to winter in Denmark, the Netherlands and the
British Isles The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebr ...
. They are common in winter in the
wildfowl The Anatidae are the biological family of water birds that includes ducks, geese, and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica. These birds are adapted for swimming, floating o ...
nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, funga, or features of geologic ...
s of the
Royal Society for the Protection of Birds The Royal Society for the Protection of Birds (RSPB) is a Charitable_organization#United_Kingdom, charitable organisation registered in Charity Commission for England and Wales, England and Wales and in Office of the Scottish Charity Regulator, ...
and of the Wildfowl & Wetlands Trust. Some birds also winter elsewhere on the southern shores of the
North Sea The North Sea lies between Great Britain, Denmark, Norway, Germany, the Netherlands, Belgium, and France. A sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian Se ...
. Bewick's swans breeding in eastern Russia migrate via Mongolia and northern China to winter in the coastal regions of Korea, Japan, and southern China, south to
Guangdong ) means "wide" or "vast", and has been associated with the region since the creation of Guang Prefecture in AD 226. The name "''Guang''" ultimately came from Guangxin ( zh, labels=no, first=t, t= , s=广信), an outpost established in Han dynasty ...
and occasionally as far as Taiwan. A few birds from the central Siberian range also winter in Iran at the south of the
Caspian Sea The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...
; in former times these flocks also migrated to the Aral Sea before the late 20th century ecological catastrophe turned most of the habitat there into inhospitable wasteland. Arrival in winter quarters starts about mid-October, though most spend weeks or even months at favorite resting locations and will only arrive in winter quarters by November or even as late as January. The birds leave winter quarters to breed starting in mid-February. Vagrants may occur south of the main wintering range in cold years and have been recorded from most European countries where the birds do not regularly winter, as well as Algeria, Iraq, Israel, Libya, Nepal, northeast Pakistan, and on the Mariana and Volcano Islands in the western Pacific. Vagrants on the spring migration have been sighted on Bear Island, Iceland and
Svalbard Svalbard ( , ), previously known as Spitsbergen or Spitzbergen, is a Norway, Norwegian archipelago that lies at the convergence of the Arctic Ocean with the Atlantic Ocean. North of continental Europe, mainland Europe, it lies about midway be ...
, and in
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
,
Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...
and
Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...
in North America. ''C. c. columbianus'' breeds in the coastal plains of Alaska and Canada, leaving for winter quarters about October. They arrive in winter quarters by November/December. Birds breeding in western Alaska winter along the Pacific coast from southern Alaska to
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
; they often move inland – particularly to the rich feeding grounds in the Central Valley – and some cross the
Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in great-circle distance, straight-line distance from the northernmost part of Western Can ...
again and winter as far east as
Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
and south to
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
and northern Mexico. The birds breeding along the
Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five oceanic divisions. It spans an area of approximately and is the coldest of the world's oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, ...
coast migrate via Canada and the
Great Lakes The Great Lakes, also called the Great Lakes of North America, are a series of large interconnected freshwater lakes spanning the Canada–United States border. The five lakes are Lake Superior, Superior, Lake Michigan, Michigan, Lake Huron, H ...
region to winter at the Atlantic coast of the United States, mainly from
Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...
to
North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...
, but some move as far south as
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
. Whistling swans start leaving for the breeding grounds again by mid-March, and arrive by late May. Vagrants have been recorded on the Bermudas, Cuba the
Hawaiian Islands The Hawaiian Islands () are an archipelago of eight major volcanic islands, several atolls, and numerous smaller islets in the Pacific Ocean, North Pacific Ocean, extending some from the Hawaii (island), island of Hawaii in the south to nort ...
,
Puerto Rico ; abbreviated PR), officially the Commonwealth of Puerto Rico, is a Government of Puerto Rico, self-governing Caribbean Geography of Puerto Rico, archipelago and island organized as an Territories of the United States, unincorporated territo ...
, and in England, Ireland, Japan, northeastern Siberia and Sweden.


Ecology and biology


Diet

In summer, their diet consists mainly of aquatic vegetation, e.g. mannagrass (''Glyceria''), '' Potamogeton'' pondweeds and marine eelgrass (''Zostera''), acquired by sticking the head underwater or upending while swimming; they also eat some grass growing on dry land. At other times of year, leftover
grain A grain is a small, hard, dry fruit (caryopsis) – with or without an attached husk, hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and ...
s and other
crop A crop is a plant that can be grown and harvested extensively for profit or subsistence. In other words, a crop is a plant or plant product that is grown for a specific purpose such as food, Fiber, fibre, or fuel. When plants of the same spe ...
s such as
potato The potato () is a starchy tuberous vegetable native to the Americas that is consumed as a staple food in many parts of the world. Potatoes are underground stem tubers of the plant ''Solanum tuberosum'', a perennial in the nightshade famil ...
es, picked up in open fields after harvest, make up much of their diet. Tundra swans forage mainly by day. In the breeding season, they tend to be territorial and are aggressive to many animals who pass by; outside the breeding season they are rather gregarious birds.


Natural predator

Healthy adult birds have few natural predators. The
Arctic fox The Arctic fox (''Vulpes lagopus''), also known as the white fox, polar fox, or snow fox, is a small species of fox native to the Arctic regions of the Northern Hemisphere and common throughout the Tundra#Arctic tundra, Arctic tundra biome. I ...
(''Vulpes lagopus''), parasitic jaegers (''Stercorarius parasiticus''), and glaucous gull (''Larus hyperboreus'') can take the eggs and hatchlings. Adults typically can stand their ground and displace foxes and birds but occasionally they are successful when both adults are absent due to disturbance or territorial dispute. Another surprisingly serious nest predator for tundra swans are
brown bear The brown bear (''Ursus arctos'') is a large bear native to Eurasia and North America. Of the land carnivorans, it is rivaled in size only by its closest relative, the polar bear, which is much less variable in size and slightly bigger on av ...
s (''Ursus arctos''), which were apparently the primary cause of nesting failure in both the Arctic National Wildlife Refuge and Izembek National Wildlife Refuge. Other potential nest predators include
red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia, plus ...
(''Vulpes vulpes''),
golden eagle The golden eagle (''Aquila chrysaetos'') is a bird of prey living in the Northern Hemisphere. It is the most widely distributed species of eagle. Like all eagles, it belongs to the family Accipitridae. They are one of the best-known bird of pr ...
s (''Aquila chrysaetos''). Brown bear, golden eagles and rarely, gray wolves (''Canis lupus'') may on occasion succeed at capturing and killing an adult. Small or avian predators usually elicit either an aggressive response or the behavior of sitting tight on nests while larger mammals, perhaps more dangerous to adults, usually elicit the response of leading the cygnets into deep waters and standing still until they pass. About 15% of the adults die each year from various causes, and thus the average lifespan in the wild is about 10 years. The oldest recorded tundra swan was over 24 years old.


Reproduction

The tundra swans mate in the late spring, usually after they have returned to the nesting grounds; as usual for swans, they pair monogamously until one partner dies. Should one partner die long before the other, the surviving bird often will not mate again for some years, or even for its entire life. The nesting season starts at the end of May. The pair build the large mound-shaped nest from plant material at an elevated site near open water, and defend a large territory around it. The pen (female) lays and incubates a
clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...
of 2–7 (usually 3–5) eggs, watching for danger while sitting on the nest. The cob (male) keeps a steady lookout for potential predators heading towards his mate and offspring. When either of them spots a threat, they give a warning sound to let their partner know that danger is approaching. Sometimes the cob will use his wings to run faster and appear larger in order to scare away a predator. The time from laying to hatching is 29–30 days for Bewick's swan and 30–32 days for the whistling swan. Since they nest in cold regions, tundra swan cygnets grow faster than those of swans breeding in warmer climates; those of the whistling swan take about 60–75 days to fledge—twice as fast as those of the mute swan for example—while those of Bewick's swan, about which little breeding data is known, may fledge a record 40–45 days after hatching already. The fledglings stay with their parents for the first winter migration. The family is sometimes even joined by their offspring from previous breeding seasons while on the wintering grounds; Tundra swans do not reach sexual maturity until 3 or 4 years of age.


Conservation status

The whistling swan is the most common swan species of North America, estimated to number almost 170,000 individuals around 1990. Its numbers seem to be slowly declining in the west of its range since the late 19th century, coincident with the expansion of human settlement and habitat conversion in the birds' wintering areas; the eastern whistling swan populations on the other hand seem to be increasing somewhat, and altogether its numbers seem to have slightly risen in the late 20th century (the population was estimated at 146,000 in 1972). Bewick's swan remains far less known; although its population is in decline in northwestern Europe, for currently unexplained reasons. The European winter population was estimated at 16,000–17,000 about 1990, with about 20,000 birds wintering in east Asia. The Iranian wintering population is small—1,000 birds or so at most—but they usually disperse to several sites, some of which are still unknown to scientists. Although tundra swan numbers are stable over most of its range, they are increasingly dependent on agricultural crops to supplement their winter diet, as aquatic vegetation in their winter habitat dwindles due to
habitat destruction Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...
and
water pollution Water pollution (or aquatic pollution) is the contamination of Body of water, water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and ...
. But the main cause of adult mortality is hunting; 4,000 whistling swans are bagged officially each year, while a further 6,000–10,000 are killed by poachers and native subsistence hunter-gatherers. Bewick's swan cannot be hunted legally, but almost half the birds studied contained lead shot in their body, indicating they were shot at by poachers.
Lead poisoning Lead poisoning, also known as plumbism and saturnism, is a type of metal poisoning caused by lead in the body. Symptoms may include abdominal pain, constipation, headaches, irritability, memory problems, infertility, numbness and paresthesia, t ...
by ingestion of lead shot is a very significant cause of mortality also, particularly in the whistling swan. The tundra swan is not considered threatened by the
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
(IUCN) due to its large range and population. The proposed
subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
''jankowskii'' was for some time placed on CITES Appendix II; it was eventually removed since it is not generally accepted as valid. Bewick's swan is one of the birds to which the '' Agreement on the Conservation of African-Eurasian Migratory Waterbirds'' (AEWA) applies. Toxic mining wastes in the Silver Valley,
Idaho Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...
in the United States has been known to be responsible for the death of migrating tundra swans.


Gallery

bewicks.head.arp.jpg, Head of a Bewick's swan, ''C. c. bewickii'' Whooper1.jpg, Head of a whooper swan, ''C. cygnus'' tundra.swan.750pix.jpg, Whistling swan, ''C. c. columbianus'' Whistling Swan RWD3.jpg, Whistling swan, ''C. c. columbianus'' Trumpeter Swan - natures pics 2.jpg, Trumpeter swan, ''C. buccinator'' Cygnus bewickii 03.jpg, Bewick's swan feeding by upending Flock-of-tundra-swans.jpg, Flock of adult and young whistling swans Tundra swans (21523232431).jpg, Tundra swans alight at Mattamuskeet National Wildlife Refuge in North Carolina


References


Further reading

*


External links


RSPB Bewick's Swan Page


* with Circumpolar Range map at bird-stamps.org * * * {{Authority control Tundra swan tundra swan Holarctic birds tundra swan Taxa named by George Ord