Swans are birds of the genusCygnus within the familyAnatidae.[4] The swans' closest relatives include thegeese andducks. Swans are grouped with the closely related geese in thesubfamilyAnserinae where they form thetribeCygnini. Sometimes, they are considered a distinct subfamily,Cygninae.
There are six living and manyextinct species of swan; in addition, there is a species known as thecoscoroba swan which is no longer considered one of thetrue swans. Swans usuallymate for life, although separation sometimes occurs, particularly following nesting failure, and if a mate dies, the remaining swan will take up with another. The number ofeggs in eachclutch ranges from three to eight.[5]
Young swans are known ascygnets, fromOld Frenchcigne orcisne (diminutive suffixet'little'), from theLatin wordcygnus, a variant form ofcycnus'swan', itself from theGreekκύκνοςkýknos, a word of the same meaning.[10][11][12] An adult male is acob, fromMiddle Englishcobbe (leader of a group); an adult female is apen.[13] A group of swans is called a bevy[citation needed] or a wedge.[14]
Description
Amute 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 familyAnatidae and are among the largest flying birds. The largest living species, including themute swan,trumpeter swan, andwhooper swan, can reach a length of over 1.5 m (59 in) and weigh over 15 kg (33 lb). Their wingspans can be over 3.1 m (10 ft).[15] Compared to the closely related geese, they are much larger and have proportionally larger feet and necks.[16] Adults also have a patch of unfeathered skin between the eyes and bill. The sexes are alike inplumage, but males are generally bigger and heavier than females.[13] The biggest species of swan ever was the extinctCygnus falconeri, a flightless giant swan known from fossils found on the Mediterranean islands ofMalta andSicily. Its disappearance is thought to have resulted from extreme climate fluctuations or the arrival of superior predators and competitors.[17]
The Northern Hemisphere species of swan have pure white plumage, but the Southern Hemisphere species are mixed black and white. The Australianblack 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 Americanblack-necked swan has a white body with a black neck.[18]
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 foursubarctic 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.[19] In the mute swan and black-necked swan, both sexes have a fleshy lump at the base of their bills on the uppermandible, known as the knob, which is larger in males and is condition dependent, changing seasonally.[20][21]
Swans are generally found in temperate environments, rarely occurring in the tropics. Four (or five) species occur in theNorthern Hemisphere, one species is found in Australia, oneextinct species was found in New Zealand and theChatham Islands, and one species is distributed in southern South America. They are absent from tropical Asia, Central America, northern South America and the entirety of Africa. One species, the mute swan, has beenintroduced to North America, Australia and New Zealand.[16]
Several species aremigratory, either wholly or partly so. The mute swan is a partial migrant, being resident over areas of Western Europe but wholly migratory in Eastern Europe and Asia. The whooper swan and tundra swan are wholly migratory, and the trumpeter swans are almost entirely migratory.[16] There is some evidence that the black-necked swan is migratory over part of its range, but detailed studies have not established whether these movements are long or short-range migration.[22]
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.[16]
Mute swan threatens a photographer inToyako, 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 monogamouspair bonds as early as 20 months.[23] "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.[24] The pair bonds are maintained year-round, even in gregarious and migratory species like thetundra swan, which congregate in large flocks in the wintering grounds.[25]
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.[26] Alongside thewhistling ducks, swans are the only anatids that will do this. The average egg size (for the mute swan) is 113 × 74 mm (4+1⁄2 x 3 in), weighing 340 g (12 oz), in a clutch size of 4 to 7, and an incubation period of 34–45 days.[27] 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.[28][29] Swans' intraspecific aggressive behaviour is shown more frequent than interspecific behaviour for food and shelter. The aggression with other species is shown more intundra swans.[30]
Systematics and evolution
Black swan inTeresópolis, BrazilTrumpeter and whooper swans, with hybrid offspring
Evidence suggests that the genusCygnus evolved in Europe or western Eurasia during theMiocene, spreading all over the Northern Hemisphere until thePliocene. When the southern species branched off is not known. The mute swan is closest to the Southern HemisphereCygnus;[31] 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 thebiogeography and appearance of thesubgenusOlor, it seems likely that these are of a more recent origin, as evidenced shows by their modern ranges (which were mostly uninhabitable during thelast ice age) and great similarity between the taxa.[1]
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 theBritish Ornithologists' Union, showCygnus 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, Australasia and southern Africa
The largest North American swan. Very similar to the whooper swan (and sometimes treated as a subspecies of it), it was hunted almost toextinction but has since recovered.
Breeds on the Arctic tundra and winters in more temperate regions ofEurasia and North America. It consists of two forms, generally considered to be subspecies.
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
Thecoscoroba 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 togeese andshelducks.[33]
Thefossil record of the genusCygnus is quite impressive, although allocation to the subgenera is often tentative; as indicated above, at least the early forms probably belong to theC. olor – Southern Hemisphere lineage, whereas the Pleistocene taxa from North America would be placed inOlor. Several prehistoric species have been described, mostly from the Northern Hemisphere. In the Mediterranean, the leg bones of the giant swan (C. falconeri) were found on the islands ofMalta andSicily; 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).
SubgenusChenopis
†New Zealand swan,Cygnus sumnerensis, an extinct species related to the black swan of Australia
Other subgenera (see above):
†Cygnus csakvarensisLambrecht 1933 [Cygnus csákvárensisLambrecht 1931a nomen nudum;Cygnanser csakvarensis(Lambrecht 1933) Kretzoi 1957;Olor csakvarensis(Lambrecht 1933) Mlíkovský 1992b] (Late Miocene of Hungary)
†Cygnus mariaeBickart 1990 (Early Pliocene of Wickieup, U.S.)
†Cygnus veraeBoev 2000 (Early Pliocene of Sofia, Bulgaria)[34]
†Cygnus liskunae(Kuročkin 1976) [Anser liskunaeKuročkin 1976] (Middle Pliocene of western Mongolia)
†Cygnus hibbardiBrodkorb 1958 (?Early Pleistocene of Idaho, U.S.)
†Cygnus sp.Louchartet al. 1998 (Early Pleistocene of Dursunlu, Turkey)
†Giant swan (Cygnus falconeri)Parker 1865 sensu Livezey 1997a [Cygnus melitensisFalconer 1868;Palaeocygnus falconeri(Parker 1865) Oberholser 1908] (Middle Pleistocene of Malta and Sicily, Mediterranean)
†Dwarf swan (Cygnus equitum)Bate 1916 sensu Livezey 1997 [Anser equitum(Bate 1916) Brodkorb 1964;Cygnus (Olor)equitumBate 1916 sensu Northcote 1988a] (Middle – Late Pleistocene of Malta and Sicily, Mediterranean)
†Cygnus lacustris(De Vis 1905) [Archaeocycnus lacustrisDe Vis 1905] (Late Pleistocene of the Lake Eyre region, Australia)
The supposed fossil swans"Cygnus" bilinicus and"Cygnus" herrenthalsi were, respectively, astork and some large bird of unknown affinity (due to the bad state of preservation of the referred material).
Many of the cultural aspects refer to the mute swan of Europe. Perhaps the best-known story about a swan is the fairy tale "The Ugly Duckling". Swans are often a symbol of love or fidelity because of their long-lasting, apparently monogamous relationships. SeeWagner's famous swan-related operasLohengrin[37] andParsifal.[38]
As food
Swan meat was regarded as a luxury food in England during the reign ofElizabeth I. A recipe for baked swan survives from that time: "To bake a Swan Scald it and take out the bones, and parboil it, then season it very well with Pepper, Salt and Ginger, then lard it, and put it in a deep Coffin of Rye Paste with store of Butter, close it and bake it very well, and when it is baked, fill up the Vent-hole with melted Butter, and so keep it; serve it in as you do the Beef-Pie."[39] Swans being raised for food were sometimes kept inswan pits.
Based on a mistaken belief that the British monarch owns all the swans in Britain, it is popularly believed the British monarch is the only person allowed to eat swans in the United Kingdom.[40][41]
The flag of theSwiss municipality ofHorgen. The swan symbolizes the town's location atLake Zurich and Horgen's political status as administrative capital ofHorgen District.
Other references in classical literature include the belief that, upon death, the mute swan would sing beautifully—hence the phraseswan song.[43]
The mute swan is also one of the sacred birds ofApollo, whose associations stem both from the nature of the bird as a symbol of light, as well as the notion of a "swan song". The god is often depicted riding a chariot pulled by or composed of swans in his ascension fromDelos.
In the second century, the Roman poetJuvenal made a sarcastic reference to a good woman being a "rare bird, as rare on earth as a black swan" (black swans being completely unknown in the Northern Hemisphere until Dutch explorers reached Australia in the 1600s), from which comes the Latin phraserara avis (rare bird).[44]
Irish lore and poetry
The Irish legend of theChildren of Lir is about a stepmother who transformed her children into swans for 900 years.[45]
In the legendThe Wooing of Etain the king of theSidhe (subterranean-dwelling, supernatural beings) transforms himself and the most beautiful woman in Ireland, Etain, into swans to escape from the king of Ireland and Ireland's armies. The swan has recently been depicted on anIrish commemorative coin.
InNorse mythology, two swans drink from the sacredWell of Urd in the realm ofAsgard, home of thegods. According to theProse Edda, the water of this well is so pure and holy that all things that touch it turn white, including this original pair of swans and all others descended from them. The poemVolundarkvida, or theLay of Volund, part of thePoetic Edda, also features swan maidens.
In the Finnish epicKalevala, a swan lives in the Tuoni River located inTuonela, the underworld realm of the dead. According to the story, whoever killed a swan would perish as well.Jean Sibelius composed theLemminkäinen Suite based on theKalevala, with the second piece entitledSwan of Tuonela(Tuonelan joutsen). Today, five flying swans are the symbol of theNordic countries; the whooper swan (Cygnus cygnus) is the national bird of Finland;[46] and the mute swan is the national bird of Denmark.[47]
Swan Lake ballet
The balletSwan Lake is among the most canonic of classical ballets. Based on the 1875–76 score byPyotr Ilyich Tchaikovsky, the most promulgated choreographic version was created byMarius Petipa andLev Ivanov (1895), the premiere of which was danced by the Imperial Ballet at theMariinsky Theater in St. Petersburg. The ballet's lead dual roles of Odette (white swan)/Odile (black swan) represent good and evil[48] and are among the most challenging roles[49] created in Romantic classical ballet. The ballet is in the repertories[50] of ballet companies around the world.
A swan is one of the attributes of St.Hugh of Lincoln, based on the story of a swan who was devoted to him.[51]
Spanish language literature
InLatin American literature, the Nicaraguan poetRubén Darío (1867–1916) consecrated the swan as a symbol of artistic inspiration by drawing attention to the constancy of swan imagery inWestern culture, beginning with the rape of Leda and ending withWagner'sLohengrin. Darío's most famous poem in this regard isBlasón – "Coat of Arms" (1896), and his use of the swan made it a symbol for theModernismo poetic movement that dominated Spanish language poetry from the 1880s until the First World War. Such was the dominance of Modernismo in Spanish language poetry that the Mexican poetEnrique González Martínez attempted to announce the end of Modernismo with asonnet provocatively entitled,Tuércele el cuello al cisne – "Wring the Swan's Neck" (1910).
Swans are revered inHinduism and are compared to saintly persons whose chief characteristic is to be in the world without getting attached to it, just as a swan's feather does not get wet although it is in water. TheSanskrit word for swan ishamsa and the "Raja Hamsam" or the Royal Swan is the vehicle of DeviSaraswati, which symbolises theSattva Guna or purity par excellence. The swan, if offered a mixture of milk and water, is said to be able to drink the milk alone. Therefore, Saraswati, the goddess of knowledge, is seen riding the swan because the swan thus symbolizesViveka, i.e. prudence and discrimination between the good and the bad or between the eternal and the transient. This is seen as a great quality, as shown by thisSanskrit verse:
haṁsaḥ śveto bakaḥ śvetaḥ ko bhedo bakahaṁsayoḥ ।
kṣīranīraviveke tu haṁso haṁsaḥ bako bakaḥ ॥
The swan is white, the crane is white, what is the difference between the swan and the crane?
During discriminating between water and milk, the swan is a swan while the crane is a crane!
It is mentioned several times in theVedic literature, and persons who have attained great spiritual capabilities are sometimes calledParamahamsa ("Supreme Swan") on account of theirspiritual grace and ability to travel between various spiritual worlds. In the Vedas, swans are said to reside in the summer onLake Manasarovar and migrate to Indian lakes for the winter. They are believed to possess some powers, such as the ability to eat pearls.
Indo-European religions
Swans are intimately associated with thedivine twins in Indo-European religions, and it is thought that inProto-Indo-European times, swans were a solar symbol associated with the divine twins and the original Indo-Europeansun goddess.[52]
^Mallory, J. P.; Adams, D. Q. (2006).The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World. New York: Oxford University Press. p. 360.ISBN0-19-928791-0.
^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.
^Schlatter, Roberto; Navarro, Rene A.; Corti, Paulo (2002). "Effects of El Nino Southern Oscillation on Numbers of Black-Necked Swans at Rio Cruces Sanctuary, Chile".Waterbirds.25 (Special Publication 1):114–122.JSTOR1522341.
^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.
^Louchart, Antoine; Vignaud, Patrick; Likius, Andossa; Mackaye, Hassane T.; Brunet, Michel (27 June 2005). "A New Swan (Aves: Anatidae) in Africa, from the Latest Miocene of Chad and Libya".Journal of Vertebrate Paleontology.25 (2):384–392.doi:10.1671/0272-4634(2005)025[0384:ANSAAI]2.0.CO;2.JSTOR4524452.S2CID85860957.
^The balletSwan Lake is among the most canonic of classical ballets. Based on the 1875-76 score by Pyotr Ilyich Tchaikovsky, the most promulgated choreographic version was created by Marius Petipa and Lev Ivanov (1895), the premiere of which was danced by the Imperial Ballet at the Mariinsky Theater in St. Petersburg. The ballet's lead dual roles of Odette/Odile represent good and evil, and are among the most challenging roles created in Romantic classical ballet.
Louchart, Antoine; Mourer-Chauviré, Cécile; Guleç, Erksin; Howell, Francis Clark & White, Tim D. (1998): L'avifaune de Dursunlu, Turquie, Pléistocène inférieur: climat, environnement et biogéographie.C. R. Acad. Sci. Paris IIA327(5): 341–346. [French with English abridged version]doi:10.1016/S1251-8050(98)80053-0
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