Editing Swan (section)

==Description==
[[File:Schwanflug22.jpg|thumb|A [[mute swan]] landing on water. Due to the size and weight of most swans, large areas of open land or water are required to successfully take off and land.]]
Swans are the largest extant members of the waterfowl family [[Anatidae]] and are among the largest flying birds. The largest living species, including the [[mute swan]], [[trumpeter swan]], and [[whooper swan]], can reach a length of over {{convert|1.5|m|in|abbr=on}} and weigh over {{convert|15|kg|lb|abbr=on}}. Their wingspans can be over {{convert|3.1|m|ft|abbr=on}}.<ref name="Madge">{{Cite book |last1=Madge |first1=Steve |last2=Burn |first2=Hilary |title=Waterfowl: An Identification Guide to the Ducks, Geese, and Swans of the World |publisher=Houghton Mifflin |year=1988 |location=Boston |isbn=978-0-395-46727-5 |url-access=registration |url=https://archive.org/details/waterfowl00stev }}</ref> Compared to the closely related geese, they are much larger and have proportionally larger feet and necks.<ref name="Ducks">{{Cite book |title=Ducks, Geese and Swans |editor=Kear, Janet |publisher=Oxford University Press |location=Oxford |year=2005 |series=Bird Families of the World |isbn=978-0-19-861008-3}}</ref> Adults also have a patch of unfeathered skin between the eyes and bill. The sexes are alike in [[plumage]], but males are generally bigger and heavier than females.<ref name=PeterYoung/> The biggest species of swan ever was the extinct ''[[Cygnus falconeri]]'', a flightless giant swan known from fossils found on the Mediterranean islands of [[Malta]] and [[Sicily]]. Its disappearance is thought to have resulted from extreme climate fluctuations or the arrival of superior predators and competitors.<ref>{{Cite web|title=Mindat.org|url=https://www.mindat.org/taxon-9721570.html|access-date=2021-11-27|website=www.mindat.org|archive-date=2021-11-27|archive-url=https://web.archive.org/web/20211127133126/https://www.mindat.org/taxon-9721570.html|url-status=live}}</ref>

The Northern Hemisphere species of swan have pure white plumage, but the Southern Hemisphere species are mixed black and white. The Australian [[black swan]] (''Cygnus atratus'') is completely black except for the white flight feathers on its wings; the chicks of black swans are light grey. The South American [[black-necked swan]] has a white body with a black neck.<ref>{{cite book |last1=Young |first1=Peter |title=Swan |date=2008 |publisher=Reaktion |location=London |isbn=978-1-86189-349-9 |pages=18–27}}</ref>

The legs of most swans are typically a dark blackish-grey colour, except for the South American black-necked swan, which has pink legs. Bill colour varies: the four [[subarctic]] species have black bills with varying amounts of yellow, and all the others are patterned red and black. Although birds do not have teeth, swans, like other Anatidae, have beaks with serrated edges that look like small jagged "teeth" as part of their beaks used for catching and eating aquatic plants and algae, but also molluscs, small fish, frogs, and worms.<ref>[http://www.rspb.org.uk/discoverandenjoynature/discoverandlearn/birdguide/name/m/muteswan/feeding.aspx "Mute Swan. Feeding"] {{webarchive|url=https://web.archive.org/web/20141225021204/http://www.rspb.org.uk/discoverandenjoynature/discoverandlearn/birdguide/name/m/muteswan/feeding.aspx |date=25 December 2014 }}, Royal Society for the Protection of Birds</ref> In the mute swan and black-necked swan, both sexes have a fleshy lump at the base of their bills on the upper [[mandible]], known as the knob, which is larger in males and is condition dependent, changing seasonally.<ref>{{cite book |last1=Young |first1=Peter |title=Swan |date=2008 |publisher=Reaktion |location=London |isbn=978-1-86189-349-9 |pages=20 and 27}}</ref><ref>Horrocks, N., Perrins, C. and Charmantier, A., 2009. Seasonal changes in male and female bill knob size in the mute swan Cygnus olor. Journal of avian biology, 40(5), pp.511-519.</ref>