Editing Swan (section)

==Systematics and evolution==
[[File:Black Swans mating in Lake Burley Griffin-1 (5549168217).jpg|thumb|Black swans mating in [[Canberra]], Australia]]
[[File:Trumpeter Swan × Whooper Swan with hybrid cygnets, Kalamazoo, Michigan 31393340.jpg|thumb|Trumpeter and whooper swans, with hybrid offspring]]
Evidence suggests that the genus ''Cygnus'' evolved in Europe or western Eurasia during the [[Miocene]], spreading all over the Northern Hemisphere until the [[Pliocene]]. When the southern species branched off is not known. The mute swan is closest to the Southern Hemisphere ''Cygnus'';<ref>{{cite book |editor1=del Hoyo | display-editors=etal|title=Handbook of the Birds of the World, Volume 1 |date=1992 |publisher=Lynx Edicions}}</ref> its habits of carrying the neck curved (not straight) and the wings fluffed (not flush) as well as its bill colour and knob indicate that its closest living relative is the black swan. Given the [[biogeography]] and appearance of the [[subgenus]] ''Olor'', it seems likely that these are of a more recent origin, as evidenced shows by their modern ranges (which were mostly uninhabitable during the [[Last glacial period|last ice age]]) and great similarity between the taxa.<ref name="Northcote 1981" />

===Phylogeny===

{{clade|style=font-size:100%;line-height:80%
|label1=Cygnus
|1={{clade
  |label1=(''Sthenelides'')
  |1=''[[Black-necked swan|C. melancoryphus]]'' (Black-necked swan)
  |2={{clade
    |label1=(''Chenopis'')
    |1=''[[Cygnus atratus|C. atratus]]'' <small>(Latham, 1790)</small> (Black swan)
    |2={{clade
      |label1=(''Cygnus'')
      |1=''[[Cygnus olor|C. olor]]'' <small>(Gmelin, 1789)</small> (Mute swan)
      |label2=(''Olor'')
      |2={{clade
        |1=''[[Cygnus buccinator|C. buccinator]]'' <small>Richardson, 1832</small> (Trumpeter swan)
        |2=''[[Cygnus cygnus|C. cygnus]]'' <small>(Linnaeus, 1758)</small> (Whooper swan)
        |3=''[[Cygnus columbianus|C. columbianus]]'' <small>(Ord, 1815)</small> (Tundra swan)<ref>{{cite web |last1=Boyd |first1=John H. |title=Anserini species tree |url=http://jboyd.net/Taxo/Anserini.pdf |access-date=22 January 2020 |archive-date=5 October 2016 |archive-url=https://web.archive.org/web/20161005063025/http://jboyd.net/Taxo/Anserini.pdf |url-status=live }}</ref>
         }}
       }}
     }}
   }}
}}

===Species===
'''Genus ''Cygnus'''''
{| class="wikitable collapsible"
|-
! Subgenus
! Image
! Scientific name
! Common name
!Description
! Distribution
|-
! rowspan="1" style="text-align:center;"| Subgenus ''Cygnus''
|[[File:Cisne (Cygnus olor) en el Palacio de Nymphenburg, Múnich, Alemania30.JPG|120px]]
|''Cygnus olor''
|[[Mute swan]]
|Eurasian species that occurs at lower latitudes than the whooper swan and Bewick's swan across Europe into southern Russia, China and the Russian Maritimes. Recent fossil records, according to the [[British Ornithologists' Union]], show ''Cygnus olor'' is among the oldest bird species still extant and it has been upgraded to "native" status in several European countries since this bird has been found in fossil and bog specimens dating back thousands of years. Common temperate Eurasian birds, often semi-domesticated descendants of domestic flocks, are naturalised in the United States and elsewhere.
|Europe into southern Russia, China and the Russian Maritimes; introduced populations in North America, Japan, Australasia and southern Africa.
|-
! rowspan="1" style="text-align:center;"| Subgenus ''Chenopis''
|[[File:Black Swan in Australia.JPG|120px]]
|''Cygnus atratus''
|[[Black swan]]
|Nomadic with erratic migration patterns dependent upon climatic conditions. Black plumage and a red bill.
|Australia, introduced into New Zealand and the [[Chatham Islands]], with additional smaller introductions in Europe, the United States, Japan and China.
|-
! rowspan="1" style="text-align:center;"| Subgenus ''Sthenelides''
|[[File:Black-necked Swans (Cygnus melancoryphus), near Chacao, Chile (25184819835).jpg|120px]]
|''Cygnus melancoryphus''
|[[Black-necked swan]]
|
|South America
|-
! rowspan="3" style="text-align:center;"| Subgenus ''Olor''
|[[File:Cygnus cygnus EM1B1735 (50023626141).jpg|120px]]
|''Cygnus cygnus''
|[[Whooper swan]]
|
|Breeds in Iceland and subarctic Europe and Asia, migrating to temperate Europe and Asia in winter
|-
|[[File:Trumpeter Swaw (Cygnus buccinator) RWD1.jpg|120px]]
|''Cygnus buccinator''
|[[Trumpeter swan]]
|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.
|North America
|-
|[[File:Bewick's Swans at Big Waters.jpg|120px]]
|''Cygnus columbianus''
|[[Tundra swan]]
|Breeds on the Arctic tundra and winters in more temperate regions of [[Eurasia]] and North America. It consists of two forms, generally considered to be subspecies but considered separate species by some authorities.<ref>{{cite web | title=Overzicht van alle vogels waargenomen in Nederland | website=Dutch Avifauna | url=https://www.dutchavifauna.nl/list. | language=nl | access-date=2025-05-17}}</ref>
* Bewick's swan ''Cygnus'' (''columbianus'') ''bewickii'' is the Eurasian form that migrates from Arctic Russia to western Europe and eastern Asia (China, Korea, Japan) in winter.
* Whistling swan ''Cygnus'' (''columbianus'') ''columbianus'' is the North American form.
|North America, Eurasia
|-
|}

The [[coscoroba swan]] (''Coscoroba coscoroba'') from South America, the only species in its genus, is not a true swan. Its phylogenetic position is not fully resolved; it is in some aspects more similar to [[Goose|geese]] and [[shelduck]]s.<ref>{{Cite web |url=https://www.zoo.org/page.aspx?pid=1842#.V6a615MrI6g |title=COSCOROBA SWAN |archive-url=https://web.archive.org/web/20160808082000/https://www.zoo.org/page.aspx?pid=1842 |archive-date=8 August 2016}}</ref>

{{Multiple image
| image1            = Mute × Whooper Swan imported from iNaturalist photo 13133281 on 6 December 2024.jpg
| image2            = Trumpeter × Whooper Swan imported from iNaturalist photo 5105993 on 6 December 2024 (cropped).jpg
| image3            = Trumpeter × Mute Swan, Morningstar Dr, Parksville, BC V9P, Canada imported from iNaturalist photo 58193430.jpg
| image4            = Trumpeter × Tundra Swan imported from iNaturalist photo 186420958 on 6 December 2024.jpg
| align             = center
| total_width       = 800
| header            = Hybrids
| caption1          = Mute x Whooper Swan
| caption2          = Trumpeter × Whooper Swan
| caption3          = Trumpeter × Mute Swan
| caption4          = Trumpeter × Tundra Swan
}}

===Fossil record===
[[File:Black Swan skeleton.jpg|thumb|upright|[[Black swan]] skeleton ([[Museum of Osteology]])]] <!--not actually a fossil-->

The [[fossil record]] of the genus ''Cygnus'' is quite impressive, although allocation to the subgenera is often tentative; as indicated above, at least the early forms probably belong to the ''C. olor'' – Southern Hemisphere lineage, whereas the Pleistocene taxa from North America would be placed in ''Olor''. Several prehistoric species have been described, mostly from the Northern Hemisphere. In the Mediterranean, the leg bones of the giant swan (''[[Cygnus falconeri|C. falconeri]]'') were found on the islands of [[Malta]] and [[Sicily]]; it may have been over 2 metres from tail to bill, which was taller (though not heavier) than the contemporary local dwarf elephants (''[[Palaeoloxodon falconeri]]'').
* Subgenus ''Chenopis''
** †[[New Zealand swan]], ''Cygnus sumnerensis'', an extinct species related to the black swan of Australia
* Other subgenera (see above):
** †''Cygnus atavus'' <small>(Fraas 1870) Mlíkovský 1992</small> [''Anas atava'' <small>Fraas 1870</small>; ''Anas cygniformis'' <small>Fraas 1870</small>; ''Palaelodus steinheimensis'' <small>Fraas 1870</small>; ''Anser atavus'' <small>(Fraas 1870) Lambrecht 1933</small>; ''Anser cygniformis'' <small>(Fraas 1870) Lambrecht 1933</small>] (Middle Miocene of Germany)
** †''Cygnus csakvarensis'' <small>Lambrecht 1933</small> [''Cygnus csákvárensis'' <small>Lambrecht 1931a nomen nudum</small>; ''Cygnanser csakvarensis'' <small>(Lambrecht 1933) Kretzoi 1957</small>; ''Olor csakvarensis'' <small>(Lambrecht 1933) Mlíkovský 1992b</small>] (Late Miocene of Hungary)<!-- AmMusNovit2369:1 -->
** †Dwarf swan (''Cygnus equitum'') <small>Bate 1916 sensu Livezey 1997</small> [''Anser equitum'' <small>(Bate 1916) Brodkorb 1964</small>; ''Cygnus'' (''Olor'') ''equitum'' <small>Bate 1916 sensu Northcote 1988a</small>] (Middle – Late Pleistocene of Malta and Sicily, Mediterranean)<!-- AmMusNovit2369:1; IntGeolCongr32FieldTripGuideBookB07; Palaeontology31:725 -->
** †[[Giant swan]] (''Cygnus falconeri'') <small>Parker 1865 sensu Livezey 1997a</small> [''Cygnus melitensis'' <small>Falconer 1868</small>; ''Palaeocygnus falconeri'' <small>(Parker 1865) Oberholser 1908</small>] (Middle Pleistocene of Malta and Sicily, Mediterranean)<!-- AmMusNovit2369:1; Ardeola51:91; Palaeontology31:725 -->
** †''Cygnus hibbardi'' <small>Brodkorb 1958</small> (?Early Pleistocene of Idaho, U.S.)<!-- AmMusNovit2369:1 -->
** †''Cygnus lacustris'' <small>(De Vis 1905)</small> [''Archaeocycnus lacustris'' <small>De Vis 1905</small>] (Late Pleistocene of the Lake Eyre region, Australia)<!-- AmMusNovit2369:1 -->
** †''Cygnus liskunae'' <small>(Kuročkin 1976)</small> [''Anser liskunae'' <small>Kuročkin 1976</small>] (Middle Pliocene of western Mongolia)
** †''Cygnus mariae'' <small>Bickart 1990</small> (Late Miocene of Florida and Early Pliocene of Arizona, USA)<ref>{{cite journal |last1=Bickart|first1=K.J.|year=1990|title=Part I: The birds of the late Miocene-early Pliocene Big Sandy Formation, Mohave County, Arizona|journal=Ornithological Monographs|volume=44|issue=1|pages=1–72|url=https://www.jstor.org/stable/40166673|doi=10.2307/40166673|jstor=40166673 }}</ref><ref>{{cite journal |last1=Steadman |first1=David |last2=Takano |first2=Oona |title=A new genus and species of heron (Aves: Ardeidae) from the late Miocene of Florida |journal=Bulletin of the Florida Museum of Natural History |url=https://par.nsf.gov/biblio/10094084-new-genus-species-heron-aves-ardeidae-from-late-miocene-florida |date=April 2019 |volume=55 |issue=9 |pages=174–186 |doi=10.58782/flmnh.qskt9951 |issn=2373-9991}}</ref>
** †''[[Cygnus paloregonus]]'' <small>Cope 1878</small> [''Anser condoni'' <small>Schufeldt 1892</small>; ''Cygnus matthewi'' <small>Schufeldt 1913</small>] (Middle Pleistocene of west-central U.S.)<!-- AmMusNovit2369:1; Auk30:29;87:537 Condor46:25 -->
** †''Cygnus verae'' <small>Boev 2000</small> (Early Pliocene of Bulgaria)<ref>Boev, Z. 2000. "''Cygnus verae'' sp. n. (Anseriformes: Anatidae) from the Early Pliocene of Sofia (Bulgaria)". ''Acta zoologica cracovienzia'', Krakow, 43 (1–2): 185–192.</ref>
** †''Cygnus'' sp. <small>Louchart ''et al''. 1998</small> (Early Pleistocene of Turkey)<ref>{{cite journal | doi=10.1016/S1251-8050(98)80053-0 | title=L'Avifaune de Dursunlu, Turquie, Pléistocène inférieur: Climat, environnement et biogéographie |trans-title=The avifauna of Dursunlu, Turkey, Lower Pleistocene: climate, environment and biogeography| date=1998 | last1=Louchart | first1=Antoine | last2=Mourer-Chauviré | first2=Cécile | last3=Guleç | first3=Erksin | last4=Howell | first4=Francis Clark | last5=White | first5=Tim D. | journal=Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science | volume=327 | issue=5 | pages=341–346 | bibcode=1998CRASE.327..341L }}</ref>
** †''Cygnus'' sp. (Pleistocene of Australia)<ref>{{Cite journal|last1=Louchart|first1=Antoine|last2=Vignaud|first2=Patrick|last3=Likius|first3=Andossa|last4=Mackaye|first4=Hassane T.|last5=Brunet|first5=Michel|date=27 June 2005|title=A New Swan (Aves: Anatidae) in Africa, from the Latest Miocene of Chad and Libya|journal=Journal of Vertebrate Paleontology|volume=25|issue=2|pages=384–392|doi=10.1671/0272-4634(2005)025[0384:ANSAAI]2.0.CO;2|jstor=4524452|s2cid=85860957 }}</ref><ref>{{Cite book|last=Sfetcu|first=Nicolae|title=The Birds World|year=2011|isbn=9781447875857}}</ref><!-- possibly one of those de Vis' taxa which are synonymous with or paleosubspecies of living birds -->
* Other genera
** † ''[[Annakacygna]]''

The supposed fossil swans ''"Cygnus" bilinicus'' and ''"Cygnus" herrenthalsi'' were, respectively, a [[stork]] and some large bird of unknown affinity (due to the bad state of preservation of the referred material).<ref name=Mlíkovský>{{cite book |last=Mlíkovský |first=Jiří  |year=2002 |title=Cenozoic Birds of the World, Part 1: Europe |publisher=Ninox Press |location=Prague |id={{Listed Invalid ISBN |80-901105-3-8}} |url=http://www.nm.cz/download/JML-18-2002-CBE.pdf|archive-url=https://web.archive.org/web/20160411215341/http://www.nm.cz/download/JML-18-2002-CBE.pdf|archive-date=11 April 2016 |page=123}}</ref>