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Family: Anatidae
Subfamily:Anserinae
Genus Coscoroba
Tribe:Cygnini
Swans, genus Cygnus, are birds of the family Anatidae,
which also includes geese and ducks. Swans are grouped with the closely
related geese in the subfamily Anserinae where they form the
tribe Cygnini. Sometimes, they are considered
a distinct subfamily, Cygninae. There are six to seven species
of swan in the genus Cygnus; in addition there is another species
known as the Coscoroba Swan, although this species is no longer considered
related to the true swans.
Swans usually mate for life, though 'divorce' does sometimes occur,
particularly following nesting failure.
The number of eggs in each clutch ranges from three to eight.
Subfamily:
Anserinae
Genus Cygnus:
Subgenus Cygnus
Mute Swan,
Cygnus olor, is a Eurasian species that occurs at lower
latitudes than Whooper Swan and
Bewick's Swan across Europe into southern Russia, China and
the Russian Maritimes.
Subgenus Chenopis
Black
Swan, Cygnus atratus of Australia, and introduced
in New Zealand.
Subgenus Sthenelides
Black-necked
Swan, Cygnus melancoryphus of South America.
Subgenus Olor
Whooper Swan,
Cygnus cygnus breeds in Iceland and subarctic Europe
and Asia, migrating
to temperate Europe
and Asia in winter.
Trumpeter Swan,
Cygnus buccinator is the largest North American swan.
Very
similar to the Whooper Swan (and sometimes treated as a
subspecies of it),
it was hunted almost to extinction but has since recovered.
Tundra Swan, Cygnus columbianus
is a small swan which breeds on the North American tundra,
further north than Trumpeter Swan. It winters in the USA.
Bewick's
Swan, Cygnus columbianus bewickii is
the Eurasian form which migrates
from Arctic Russia to western
Europe and eastern Asia (China, Japan) in winter.
Whistling
Swan,
Cygnus columbianus columbianus,
Genus Coscoroba
Coscoroba Swan, Coscoroba coscoroba
Coscoroba
Swan at Slimbridge Wildfowl and Wetlands Centre, England
Photo: Adrian Pingstone
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1) The Coscoroba Swan, Coscoroba coscoroba, is a species
of waterfowl inhabiting southern South
America. It is the smallest of the birds called "swans",
but still a large species of waterfowl, averaging
4.2 kg (9.3 lbs), 1 m (3.3 ft) long and 1.57 m (5.2 ft) across
the wings. It belongs to the subfamily
Anserinae in the family of ducks, swans, and geese, Anatidae.
It is placed in the monotypic genus Coscoroba.
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List of norwegian names: Source:
Norsk Ornitologisk Forening
Bewick's
Swan, Jan. 2006, Saitama JAPAN
Photo: Maga-chan
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The Tundra Swan, Cygnus columbianus, is a small
Holarctic swan. The two taxa within it are usually regarded
as conspecific, but are also sometimes split into two species,
Cygnus bewickii, Bewick's Swan of the Palaearctic and
the Whistling Swan,
Cygnus columbianus proper, of the Nearctic. Birds from
eastern Russia (roughly east of the Taimyr Peninsula) are
sometimes separated as the subspecies Cygnus columbianus
jankowskii, but this is not widely accepted as distinct,
most
authors including them in Cygnus columbianus bewickii.
Tundra Swans are sometimes separated in the genus Olor together
with the other Arctic swan species.
The Tundra Swan, Cygnus columbianus is the smallest
of the Holarctic swans, at 115–150 cm in length, 168–211
cm in
wingspan and a weight range of 3.4–9.6 kg. In adult birds,
the plumage of both subspecies 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 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, Cygnus columbianus bewickii.
Bewick's Swans are the smaller subspecies. There is a slight
size cline, with the eastern birds being slightly larger; good
measurement data only exists for the western populations however.
These weigh 3.4–7.8 kg, 6.4 kilograms on average in
males and 5.7 kilograms in females. They measure 115–140
cm in overall length; each wing is 47–55 cm long, on average
52 centimetres in males and 50.4 centimetres in females. The
tarsus measures 9.2–11.6 cm in length, the bill 8.2–10.2
cm
averaging 9.1 centimetres. Bewick's Swan is similar in appearance
to the parapatric Whooper Swan,
Cygnus 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.
Bewick's Swan is named after the engraver Thomas Bewick, who
specialised in illustrations of birds and animals.
Whistling
Swan, Cygnus columbianus columbianus,
Pine Grove Waterfowl Park, Virginia.
Photo: Dick Daniels
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Whistling Swans weigh4.3–9.5 kg 7.3 kg on average
in males and 6.4 kg in females –, and measure 120–150
cm in length.
Each wing is 50–57 cm long; the tarsus measures 9.4–11
cm in length, and the bill is 9.1–11 cm long.
Cygnus columbianus columbianus is distinguished from
Cygnus columbianus 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 Trumpeter
Swan, Cygnus 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.
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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
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-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.
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