Editing Swan (section)

==Behaviour==
[[File:Swans with nest and eggs at Lake Constance.jpg|thumb|left|Swans with nest and eggs at [[Lake Constance]]]]
[[File:Courting swan on Danube.jpg|thumb|Courting swan on the [[Danube]] river]]
Swans feed in water and on land. They are almost entirely herbivorous, although they may eat small amounts of aquatic animals. In the water, food is obtained by up-ending or dabbling, and their diet is composed of the roots, tubers, stems and leaves of aquatic and submerged plants.<ref name="Ducks" />

[[File:The swan attacks man.Hokkaido-toyako,人を襲う洞爺湖の白鳥P6200258モザイク.jpg|thumb|right|Mute swan threatens a photographer in [[Tōyako, Hokkaido|Toyako]], Japan]]
A familiar behaviour of swans is that they mate for life, and typically bond even before they reach sexual maturity. Trumpeter swans, for example, can live as long as 24 years and only start breeding at the age of 4–7, forming monogamous [[pair bond]]s as early as 20 months.<ref>{{cite journal |last=Ross |first=Drew |url=https://books.google.com/books?id=AYyqe06fpS0C&pg=PA35 |journal=National Parks |date=March–April 1998 |volume=72 |issue=3–4 |page=35 |title=Gaining Ground: A Swan's Song |url-status=live |archive-url=https://web.archive.org/web/20140326224550/http://books.google.com/books?id=AYyqe06fpS0C&pg=PA35 |archive-date=26 March 2014 }}</ref> "Divorce", though rare, does occur; one study of mute swans shows a 3% rate for pairs that breed successfully and 9% for pairs that do not.<ref>{{cite web|url=https://www.audubon.org/news/till-death-do-them-part-8-birds-mate-life/|title=Till Death do them Part: 8 Birds that Mate for Life|first=Michele|last=Berger|date=11 June 2018|publisher=National Academies Press (US)|access-date=11 June 2018|via=www.audubon.org|archive-date=12 June 2018|archive-url=https://web.archive.org/web/20180612142009/https://www.audubon.org/news/till-death-do-them-part-8-birds-mate-life/|url-status=live}}</ref> The pair bonds are maintained year-round, even in gregarious and migratory species like the [[tundra swan]], which congregate in large flocks in the wintering grounds.<ref>{{Cite journal |last=Scott |first=D. K. |year=1980 |title=Functional aspects of the pair bond in winter in Bewick's swans (''Cygnus columbianus bewickii'') |journal=Behavioral Ecology and Sociobiology |volume=7 |issue=4 |pages=323–327 |doi=10.1007/BF00300673|bibcode=1980BEcoS...7..323S |s2cid=32804332 }}</ref>

Swans' nests are on the ground near water and about a metre (3') across. Unlike many other ducks and geese, the male helps with the nest construction, and will also take turns incubating the eggs.<ref>{{cite book |last1=Scott |first1=Dafila |title=Swans |date=1995 |publisher=Colin Baxter Photography |location=Grantown-on-Spey, Scotland |isbn=978-0-948661-63-1 |page=51}}</ref> Alongside the [[whistling duck]]s, swans are the only anatids that will do this. The average egg size (for the mute swan) is 113 × 74&nbsp;mm ({{frac|4|1|2}} x 3 in), weighing 340 g (12&nbsp;oz), in a clutch size of 4 to 7, and an incubation period of 34–45 days.<ref name="BTO">[http://blx1.bto.org/birdfacts/results/bob1520.htm "Mute Swan"] {{Webarchive|url=https://archive.today/20120708230834/http://blx1.bto.org/birdfacts/results/bob1520.htm |date=2012-07-08 }}. British Trust for Ornithology</ref> Swans are highly protective of their nests. They will viciously attack anything that they perceive as a threat to their chicks, including humans. One man was suspected to have drowned in such an attack.<ref>{{cite news |last=Waldren |first=Ben |date=16 April 2012 |url=https://news.yahoo.com/blogs/abc-blogs/killer-swan-blamed-mans-drowning-120835237--abc-news-topstories.html |title=Killer Swan Blamed for Man's Drowning |publisher=Yahoo News |url-status=live |archive-url=https://web.archive.org/web/20140807182722/http://news.yahoo.com/blogs/abc-blogs/killer-swan-blamed-mans-drowning-120835237--abc-news-topstories.html |archive-date=7 August 2014 }}</ref><ref>{{cite news |url=https://www.bbc.co.uk/news/magazine-17736292 |work=BBC News |title=Who, What, Why: How dangerous are swans? |date=17 April 2012 |url-status=live |archive-url=https://web.archive.org/web/20120417181615/http://www.bbc.co.uk/news/magazine-17736292 |archive-date=17 April 2012 }}</ref> Swans' intraspecific aggressive behaviour is shown more frequent than interspecific behaviour for food and shelter. The aggression with other species is shown more in [[tundra swan]]s.<ref>{{Cite journal|last1=Wood|first1=Kevin A.|last2=Ham|first2=Phoebe|last3=Scales|first3=Jake|last4=Wyeth|first4=Eleanor|last5=Rose|first5=Paul E.|date=7 August 2020|title=Aggressive behavioural interactions between swans (Cygnus spp.) and other waterbirds during winter: a webcam-based study|journal=Avian Research|volume=11|issue=1|pages=30|doi=10.1186/s40657-020-00216-7|issn=2053-7166|doi-access=free|hdl=10871/126306|hdl-access=free}}</ref>