It is the American counterpart and a close relative of the whooper swan ( " Cygnus cygnus " ) of Eurasia, and even has been considered the same species by some authorities.
2.
Today, five flying swans are the symbol of the Nordic Countries, the whooper swan ( " Cygnus cygnus " ) is the national bird of Finland, and the mute swan is the national bird of Denmark.
3.
However, the whooper swan ( " Cygnus cygnus " ), a winter visitor to parts of the eastern Mediterranean, does possess a'bugling'call, and has been noted for issuing a drawn-out series of notes as its lungs collapse upon expiry, both being a consequence of an additional tracheal loop within its sternum.
4.
Three species ( Greenland white-fronted goose ( " Anser albifrons flavirostris " ), whooper swan ( " Cygnus cygnus " ), and golden plover ( " Pluvialis apricaria " ) ) are listed on Annex I of the directive, requiring special conservation measures concerning their habitat in order to ensure their survival and reproduction.
5.
"Zostera noltii " plays an important part in the winter diet of the whooper swan ( " Cygnus cygnus " ), the mute swan ( " Cygnus olor " ), the brent goose ( " Branta bernicla " ) and the wigeon ( " Anas penelope " ) and in fact, overwinting populations of brent goose in Europe have declined since wasting disease has become established and reduced the quantity of eel grass available.
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