Editing Common tern

{{Short description|Migratory seabird in the family Laridae with circumpolar distribution}}
{{Featured article}}
{{EngvarB|date=July 2022}}
{{Use dmy dates|date=July 2022}}

{{Speciesbox
| status            = LC
| status_system     = IUCN3.1
| status_ref        = <ref name="iucn status 12 November 2021">{{cite iucn|author=BirdLife International|date=2019|title=''Sterna hirundo''|volume=2019|page=e.T22694623A155537726|doi=10.2305/IUCN.UK.2019-3.RLTS.T22694623A155537726.en|access-date=12 November 2021}}</ref>
| image             = 2014-05-18 Sterna hirundo, Killingworth Lake, Northumberland 02.jpg
| image2            = Sterna-hirundo-002.ogg
| genus             = Sterna
| species           = hirundo
| authority         = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]
| range_map         = SternaHirundoIUCNver2018 2.png
| range_map_alt     = Map showing the breeding range of ''Sterna hirundo'' (most of temperate Northern Hemisphere), and wintering areas (coasts in tropics and Southern Hemisphere).
| range_map_caption = {{leftlegend|#00FF00|Breeding|outline=gray}} {{leftlegend|#008000|Resident|outline=gray}} {{leftlegend|#007FFF|Non-breeding|outline=gray}} {{leftlegend|#00FFFF|Passage|outline=gray}} {{leftlegend|#FF00FF|Vagrant (seasonality uncertain)|outline=blue}}
| synonyms          = *''Sterna fluviatilis'' {{small|(Naumann, 1839)}}
}}

[[File:Common-tern,web.jpg|thumbnail|Twisted head]]

The '''common tern'''<ref name = gill>{{cite web| editor = Gill, F| editor2 = Donsker D| title= IOC World Bird Names (v 2.11)|url=http://www.worldbirdnames.org/n-shorebirds.html | publisher= International Ornithologists' Union| access-date = 15 May 2014 | archive-url = https://web.archive.org/web/20131205171302/http://www.worldbirdnames.org/n-shorebirds.html | archive-date=5 December 2013}}</ref> ('''''Sterna hirundo''''') is a [[seabird]] in the family [[Laridae]]. This bird has a [[circumpolar distribution]], its four [[subspecies]] breeding in [[Temperateness|temperate]] and [[subarctic]] regions of Europe, Asia and North America. It is strongly [[bird migration|migratory]], wintering in coastal [[Tropics|tropical]] and [[Subtropics|subtropical]] regions. Breeding adults have light grey upperparts, white to very light grey underparts, a black cap, orange-red legs, and a narrow pointed bill. Depending on the subspecies, the bill may be mostly red with a black tip or all black. There are several similar species, including the partly [[Sympatry|sympatric]] [[Arctic tern]], which can be separated on [[plumage]] details, leg and bill colour, or [[Bird vocalization|vocalisation]]s.

Breeding in a wider range of habitats than any of its relatives, the common tern nests on any flat, poorly vegetated surface close to water, including beaches and islands, and it readily adapts to artificial substrates such as floating rafts. The nest may be a bare [[Bird nest#Scrape|scrape]] in sand or gravel, but it is often lined or edged with whatever debris is available. Up to three eggs may be laid, their dull colours and blotchy patterns providing [[camouflage]] on the open beach. [[Egg incubation#Avian incubation|Incubation]] is by both sexes, and the eggs hatch in around 21–22 days, longer if the colony is disturbed by predators. The downy chicks [[fledge]] in 22–28 days. Like most terns, this species feeds by plunge-diving for fish, either in the sea or in freshwater, but [[Mollusca|mollusc]]s, [[crustacean]]s and other [[invertebrate]] prey may form a significant part of the diet in some areas.

Eggs and young are vulnerable to predation by mammals such as [[rat]]s and [[American mink]], and large birds including [[gull]]s, [[owl]]s and [[heron]]s. Common terns may be infected by [[lice]], [[parasitic worm]]s, and [[mite]]s, although [[Haematozoa|blood parasites]] appear to be rare. Its large population and huge breeding range mean that this species is classed as being of [[least concern]], although numbers in North America have declined sharply in recent decades. Despite international legislation protecting the common tern, in some areas, populations are threatened by [[habitat loss]], pollution, or the disturbance of [[Bird colony|breeding colonies]].

==Taxonomy==
[[Tern|Terns]] are small to medium-sized seabirds closely related to the [[gull]]s, [[Skimmer (bird)|skimmer]]s and [[skua]]s. They are gull-like in appearance, but typically have a lighter build, long pointed wings (which give them a fast, buoyant flight), a deeply forked tail, slender legs,<ref name = BWP764/> and webbed feet.<ref name= wassink>Wassink & Ort (1995) p. 78.</ref> Most species are grey above and white below, and have a black cap which is reduced or flecked with white in the non-breeding season.<ref name = BWP764>Snow & Perrin (1998) p. 764.</ref>

The common tern's closest relatives appear to be the [[Antarctic tern]],<ref name= nisbet/> followed by the [[Eurasia]]n Arctic and [[roseate tern]]s. [[Gene]]tic evidence suggests that the common tern may have diverged from an ancestral stock earlier than its relatives.<ref name=bridge>{{cite journal|last=Bridge |first=Eli S |author2=Jones, Andrew W |author3=Baker, Allan J |year=2005 |title=A phylogenetic framework for the terns (Sternini) inferred from mtDNA sequences: implications for taxonomy and plumage evolution |journal=Molecular Phylogenetics and Evolution |volume=35 |pages=459–469 |url=http://scholar.library.csi.cuny.edu/~fburbrink/Courses/Vertebrate%20systematics%20seminar/Bridge%20et%20al%202005%20.pdf |doi=10.1016/j.ympev.2004.12.010 |pmid=15804415 |issue=2 |bibcode=2005MolPE..35..459B |archive-url=https://web.archive.org/web/20110419093510/http://scholar.library.csi.cuny.edu/~fburbrink/Courses/Vertebrate%20systematics%20seminar/Bridge%20et%20al%202005%20.pdf |archive-date=19 April 2011}}</ref> No [[fossil]]s are known from North America, and those claimed in Europe are of uncertain age and species.<ref name= nisbet/>

The common tern was first described by [[Carl Linnaeus]] in his landmark 1758 [[10th edition of Systema Naturae|10th edition of ''Systema Naturae'']] under its current scientific name, ''Sterna hirundo''.<ref name = Linnaeus>{{cite book | last=Linnaeus | first=Carolus |author-link=Carl Linnaeus | title=Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata. | publisher=Holmiae. (Laurentii Salvii)| year=1758| page= [https://www.biodiversitylibrary.org/item/10277#page/155/mode/1up 137]|language=la}}</ref> "Stearn" was used in [[Old English]], and a similar word was used by the [[Frisians]] for the birds.<ref name=OED>{{OED|Sterna}} Library subscription required.</ref> "Stearn" appears in the poem ''[[The Seafarer (poem)|The Seafarer]]'', written around 1000 A.D.<ref name=OED/> Linnaeus adopted this word for the genus name ''Sterna''. The Latin for [[swallow]] is ''hirundo,'' and refers here to the tern's superficial likeness to that unrelated bird, which has a similar light build and long forked tail.<ref name = hume12>Hume (1993) pp. 12–13.</ref> This resemblance also leads to the informal name "sea swallow",<ref name = rspb>{{cite web |title=Common tern |work=Birdguide |url=http://www.birdlife.org/datazone/speciesfactsheet.php?id=3270 |publisher=[[Royal Society for the Protection of Birds]] (RSPB) |access-date=25 January 2012 |archive-date=15 October 2016 |archive-url=https://web.archive.org/web/20161015233814/http://www.birdlife.org/datazone/speciesfactsheet.php?id=3270 |url-status=live }}</ref> recorded from at least the seventeenth century.<ref name= hume12/> The [[Scots language|Scots]] names ''picktarnie'',<ref>[http://www.dsl.ac.uk/getent4.php?query=pictarnie&sset=1&fset=20&printset=20&searchtype=full&dregion=form&dtext=all SND: Pictarnie] {{webarchive |url=https://web.archive.org/web/20130530115330/http://www.dsl.ac.uk/getent4.php?query=pictarnie&sset=1&fset=20&printset=20&searchtype=full&dregion=form&dtext=all |date=30 May 2013}}</ref> ''tarrock''<ref>[http://www.dsl.ac.uk/getent4.php?query=tarrock&sset=1&fset=20&printset=20&searchtype=full&dregion=form&dtext=all SND: tarrock] {{webarchive |url=https://web.archive.org/web/20130530115326/http://www.dsl.ac.uk/getent4.php?query=tarrock&sset=1&fset=20&printset=20&searchtype=full&dregion=form&dtext=all |date=30 May 2013}}</ref> and their many variants are also believed to be [[Onomatopoeia|onomatopoeic]], derived from the distinctive call.<ref name = hume12/> Because of the difficulty in distinguishing the two species, all the informal common names are shared with the [[Arctic tern]].<ref name=cocker>Cocker & Mabey (2005) pp. 246–247.</ref> There was some uncertainty whether ''Sterna hirundo'' should apply to the common tern or the arctic tern as the species are very similar and both occur in Sweden. In 1913, the Swedish zoologist [[Einar Lönnberg]] concluded that the [[Binomial nomenclature|binomial name]] ''Sterna hirundo'' applied to the common tern.<ref>{{cite journal | last=Lönnberg | first=Einar | author-link=Einar Lönnberg | date=1913 | title=On ''Sterna hirundo'' Linn. and on the name of the Common Tern | journal=Ibis | volume=1 | issue=2 | pages=301–303 | doi=10.1111/j.1474-919X.1913.tb06553.x | url=https://www.biodiversitylibrary.org/page/26514527 | access-date=16 August 2021 | archive-date=16 August 2021 | archive-url=https://web.archive.org/web/20210816133723/https://www.biodiversitylibrary.org/page/26514527 | url-status=live }}</ref>

Four subspecies of the common tern are generally recognized, although ''S.{{nbs}}h.{{nbs}}minussensis'' is sometimes considered an [[Intergradation|intergrade]] between ''S.{{nbs}}h.{{nbs}}hirundo'' and ''S.{{nbs}}h.{{nbs}}longipennis''.<ref name = hume88>Hume (1993) pp. 88–89.</ref><ref>{{cite web |title=''Sterna hirundo'' Linnaeus (1758) |url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=176888 |publisher=Integrated Taxonomic Information System (ITIS) |access-date=23 January 2012 |archive-date=18 October 2011 |archive-url=https://web.archive.org/web/20111018173444/http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=176888 |url-status=live }}</ref>

{| class="wikitable plainrowheaders"
|-
!scope="col" width=15% | Subspecies
!scope="col" width=15% | Image
!scope="col" width=20% | Breeding range
!scope="col" width=50% | Distinctive features
|-
!scope="row"| ''S. h. hirundo'' <br />Linnaeus, 1758
| [[File:2014-05-18 Sterna hirundo, Killingworth Lake, Northumberland 04.jpg|180px]]<br>Northumberland, UK
| Europe, North Africa, Asia east to western [[Siberia]] and [[Kazakhstan]], and North America.<ref name =olsen>Olsen & Larsson (1995) pp. 77–89.</ref>
| Differences between the North American and Eurasian populations are minimal. North American birds have a slightly shorter wing length on average, and the extent of the black tip on the upper mandible tends to be less than in birds from Scandinavia and further east in Eurasia. The proportion of black on the bill is at its minimum in the west of Europe, so British breeders are very similar to North American birds in this respect.<ref name =olsen/>
|-
!scope="row"| ''S. h. tibetana'' <br />[[Howard Saunders|Saunders]], 1876
| [[File:Common Tern, Kathmandu Valley, Nepal 1.jpg|180px]]<br>Kathmandu Valley, Nepal
| [[Himalayas]] to southern Mongolia and China.<ref name =olsen/>
| Like the nominate subspecies, but with a shorter bill and a broader black tip.<ref name=olsen/>
|-
!scope="row"| ''S. h. minussensis'' <br />[[Petr Petrovich Sushkin|Sushkin]], 1925
| [[File:Sterna hirundo, Ob River, Novosibirsk, Russia 1.jpg|180px]]<br>Novosibirsk, Russia
| [[Lake Baikal]] east to [[Outer Mongolia|northern Mongolia]] and southern [[Tibet]].<ref name= brazil/>
| Paler upper body and wings than ''S. h. longipennis'', black-tipped crimson bill.<ref name= brazil>Brazil (2008) p. 220.</ref>
|-
!scope="row"| ''S. h. longipennis''<br /> [[Alexander von Nordmann|Nordmann]], 1835
| [[File:Sterna hirundo longipennis, Tangshan, Hebei, China 01.jpg|180px]]<br>Hebei, China
| Central Siberia to China, also [[Alaska]].<ref name =olsen/>
| Darker grey than the nominate subspecies, with shorter black bill, darker red-brown legs, and longer wings.<ref name=olsen/>
|-
|}

==Description==
[[File:Sterna hirundo in Finland.jpg|thumb|Adult ''S. h. hirundo'' in the harbour of [[Jyväskylä]], Finland]]
[[File:Sterna hirundo -Nantucket National Wildlife Refuge, Massachusetts, USA -head-8.jpg|thumb|Adult ''S. h. hirundo'' in breeding plumage at [[Nantucket National Wildlife Refuge]], Massachusetts]]

The nominate subspecies of the common tern is {{convert|31|-|35|cm|abbr=on}} long, including a {{convert|6|-|9|cm|abbr=on}} fork in the tail, with a {{convert|77|-|98|cm|abbr=on}} wingspan. It weighs {{convert|110|-|141|g|abbr=on}}.<ref name=olsen/> Breeding adults have pale grey upperparts, very pale grey underparts, a black cap, orange-red legs, and a narrow pointed bill that can be mostly red with a black tip, or all black, depending on the subspecies.<ref name=hume21>Hume (1993) pp. 21–29.</ref> The common tern's upper wings are pale grey, but as the summer wears on, the dark feather shafts of the outer [[flight feather]]s become exposed, and a grey wedge appears on the wings. The rump and tail are white, and on a standing bird the long tail extends no further than the folded wingtips, unlike the Arctic and roseate terns in which the tail protrudes beyond the wings. There are no significant differences between the sexes.<ref name=vinicombe/> In non-breeding adults, the forehead and underparts become white, the bill is all black or black with a red base, and the legs are dark red or black.<ref name=vinicombe/> The upper wings have an obvious dark area at the front edge of the wing, the carpal bar. Terns that have not bred successfully may [[Moulting|moult]] into non-breeding adult plumage beginning in June, though late July is more typical, with the moult suspended during migration. There is also some geographical variation; [[California]]n birds are often in non-breeding plumage during migration.<ref name=olsen/>

Juvenile common terns have pale grey upper wings with a dark carpal bar. The crown and [[nape]] are brown, and the forehead is ginger, wearing to white by autumn. The upper parts are ginger with brown and white scaling, and the tail lacks the adult's long outer feathers.<ref name =olsen/> Birds in their first post-juvenile plumage, which normally remain in their wintering areas, resemble the non-breeding adult, but have a duskier crown, dark carpal bar, and often very worn plumage. By their second year, most young terns are either indistinguishable from adults, or show only minor differences such as a darker bill or white forehead.<ref name= harrison/>

The common tern is an agile flyer, capable of rapid turns and swoops, hovering, and vertical take-off. When commuting with fish, it flies close to the surface in a strong head wind, but {{convert|10|-|30|m|abbr=on}} above the water in a following wind. Unless migrating, normally it stays below {{convert|100|m|abbr=on}}, and averages {{convert|30|kph|abbr=on}} in the absence of a tail wind.<ref name= nisbet/> Its average flight speed during the [[nocturnal]] migration flight is {{convert|43|-|54|kph|abbr=on}}<ref name= alerstam>{{cite journal |last=Alerstam |first=T |year=1985 |title=Strategies of migratory flight, illustrated by Arctic and common terns, ''Sterna paradisaea'' and ''Sterna hirundo'' |journal=Contributions to Marine Science |volume=27 |issue=supplement on migration: mechanisms and adaptive significance |pages=580–603}}</ref> at a height of {{convert|1000|-|3000|m|abbr=on}}.<ref name= nisbet/>

===Moult===
[[File:Commonternprimary.jpg|thumb|Detail of primary feather|300px]]

Juveniles moult into adult plumage in its first October; first the head, tail, and body plumage is replaced, mostly by February, then the wing feathers. The [[Flight feather#Primaries|primaries]] are replaced in stages; the innermost feathers moult first, then replacement is suspended during the southern winter (birds of this age staying in their wintering areas) and recommences in the autumn. In May to June of the second year, a similar moult sequence starts, with a pause during primary moult for birds that return north, but not for those that stay in the winter quarters. A major moult to adult breeding plumage occurs in the next February to June, between forty and ninety per cent of feathers being replaced.<ref name=olsen/> Old primary feathers wear away to reveal the blackish barbs beneath. The moult pattern means that the oldest feathers are those nearest the middle of the wing, so as the northern summer progresses, a dark wedge appears on the wing because of this feather ageing process.<ref name=hume21/>

Terns are unusual in the frequency in which they moult their primaries, which are replaced at least twice, occasionally three times in a year. The visible difference in feather age is accentuated in the greater [[ultraviolet]] reflectance of new primaries, and the freshness of the wing feathers is used by females in mate selection.<ref name= bridgeeaton>{{cite journal |last=Bridge |first=Eli S |author2=Eaton, Muir D |year=2005 |title=Does ultraviolet reflectance accentuate a sexually selected signal in terns? |journal=Journal of Avian Biology |volume=36 |issue=1 |pages=18–21 |doi=10.1111/j.0908-8857.2005.03470.x}}</ref> Experienced females favour mates which best show their [[Fitness (biology)|fitness]] through the quality of their wing feathers.<ref name=bridge2004>{{cite journal |last=Bridge |first=Eli S |author2=Nisbet, Ian C T |year=2004 |title=Wing molt and assortative mating in Common Terns: a test of the molt-signaling hypothesis |journal=Condor |volume=106 |issue=2 |pages=336–343 |doi=10.1650/7381|s2cid=84393348 |doi-access=free }}</ref> Rarely, a very early moult at the nesting colony is linked to breeding failure, both the onset of moult and reproductive behaviour being linked to falling levels of the [[hormone]] [[prolactin]].<ref name=BB105>{{cite journal |last=Braasch |first=Alexander |author2=Garciá, Germán O |year=2012 |title=A case of aberrant post-breeding moult coinciding with nest desertion in a female Common Tern |journal=British Birds |volume=105 |pages=154–159}}</ref>

===Similar species===


There are several terns of a similar size and general appearance to the common tern. A traditionally difficult species to separate is the Arctic tern, and until the key characteristics were clarified, distant or flying birds of the two species were often jointly recorded as "commic terns". Although similar in size, the two terns differ in structure and flight. The common tern has a larger head, thicker neck, longer legs, and more triangular and stiffer wings than its relative, and has a more powerful, direct flight.<ref name= BB86/> Arctic terns have greyer underparts than the common variety, which makes its white cheeks more obvious, whereas the rump of the common tern can be greyish in non-breeding plumage, compared to the white of its relative. The common tern develops a dark wedge on the wings as the breeding season progresses, but the wings of the Arctic stay white throughout the northern summer. All the [[flight feather]]s of the Arctic tern are translucent against a bright sky, only the four innermost wing feathers of the common tern share this property.<ref name=BB86/><ref name=vanDuivendijk/> The trailing edge of the outer flight feathers is a thin black line in the Arctic tern, but thicker and less defined in the common.<ref name=vinicombe/> The bill of an adult common tern is orange-red with a black tip, except in black-billed ''S.{{nbs}}h.{{nbs}}longipennis'', and its legs are bright red, while both features are a darker red colour in the Arctic tern, which also lacks the black bill tip.<ref name=BB86>{{cite journal |last=Hume |first=Rob A |year=1993 |title=Common, Arctic and Roseate Terns: an identification review |journal=British Birds |volume=86 |pages=210–217}}</ref>

In the breeding areas, the roseate tern can be distinguished by its pale plumage, long, mainly black bill and very long tail feathers.<ref name=vanDuivendijk>van Duivendijk (2011) pp. 200–202.</ref> The non-breeding plumage of roseate is pale above and white, sometimes pink-tinged, below. It retains the long tail streamers, and has a black bill.<ref name=olsen2>Olsen & Larsson (1995) pp. 69–76.</ref> In flight, the roseate's heavier head and neck, long bill and faster, stiffer wingbeats are also characteristic.<ref name=Blomdahl>Blomdahl et al. (2007) p. 340.</ref> It feeds further out to sea than the common tern.<ref name=olsen2/> In North America, the [[Forster's tern]] in breeding plumage is obviously larger than the common, with relatively short wings, a heavy head and thick bill, and long, strong legs; in all non-breeding plumages, its white head and dark eye patch make the American species unmistakable.<ref name=olsen3>Olsen & Larrson (1995) pp. 103–110.</ref>

In the wintering regions, there are also confusion species, including the Antarctic tern of the southern oceans, the [[South American tern]], the [[Australasia]]n [[white-fronted tern]] and the [[white-cheeked tern]] of the [[Indian Ocean]]. The plumage differences due to "opposite" breeding seasons may aid in identification. The Antarctic tern is more sturdy than the common, with a heavier bill. In breeding condition, its dusky underparts and full black cap outline a white cheek stripe. In non-breeding plumages, it lacks, or has only an indistinct, carpal bar, and young birds show dark bars on the [[Flight feather#Tertials|tertials]], obvious on the closed wing and in flight.<ref name=Enticott196>Enticott & Tipling (2002) p. 196.</ref><ref name=SASOL>Sinclair et al. (2002) p. 212.</ref> The South American tern is larger than the common, with a larger, more curved red bill, and has a smoother, more extensive black cap in non-breeding plumage.<ref name=peru>Schulenberg et al. (2010) p. 154.</ref> Like Antarctic, it lacks a strong carpal bar in non-breeding plumages, and it also shares the distinctive barring of the tertials in young birds.<ref name=Enticott192>Enticott & Tipling (2002) p. 192.</ref> The white-fronted tern has a white forehead in breeding plumage, a heavier bill, and in non-breeding plumage is paler below than the common, with white underwings.<ref name=Simpson/> The white-cheeked tern is smaller, has uniform grey upperparts, and in breeding plumage is darker above with whiter cheeks.<ref name=grimmett>Grimmett et al. (1999) pp. 140–141.</ref>

Juvenile common terns are easily separated from similar-aged birds of related species. They show extensive ginger colouration to the back, and have a pale base to the bill. Young Arctic terns have a grey back and black bill, and juvenile roseate terns have a distinctive scalloped "saddle".<ref name=vinicombe>Vinicombe et al. (1990) pp. 133–138.</ref> [[Hybrid (biology)|Hybrids]] between common and roseate terns have been recorded, particularly from the US, and the intermediate plumage and calls shown by these birds is a potential identification pitfall. Such birds may have more extensive black on the bill, but confirmation of mixed breeding may depend on the exact details of individual flight feathers.<ref name=olsen/>

===Voice===
Common terns have a wide repertoire of calls, which have a lower pitch than the equivalent calls of Arctic terns. The most distinctive sound is the [[Alarm signal|alarm]] ''KEE-yah'', stressed on the first syllable, in contrast to the second-syllable stress of the Arctic tern. The alarm call doubles up as a warning to intruders, although serious threats evoke a ''kyar'', given as a tern takes flight, and quietens the usually noisy colony while its residents assess the danger.<ref name=hume68/> A down-slurred {{not a typo|''keeur''}} is given when an adult is approaching the nest while carrying a fish, and is possibly used for individual recognition (chicks emerge from hiding when they hear their parents giving this call). Another common call is a ''kip'' uttered during social contact. Other vocalizations include a ''kakakakaka'' when attacking intruders, and a staccato ''kek-kek-kek'' from fighting males.<ref name=hume68>Hume (1993) pp. 68–75.</ref>

Parents and chicks can locate one another by call, and [[sibling]]s also recognise each other's vocalisations from about the twelfth day from hatching, which helps to keep the brood together.<ref name= sibling>{{cite journal | last= Burger | first= Joanna | author2= Gochfeld, Michael | author3= Boarman, William I | year= 1988 | title= Experimental evidence for sibling recognition in Common Terns (''Sterna hirundo'') | journal= Auk | volume= 105 | issue= 1 | pages= 142–148 | jstor= 4087337 | url= http://sora.unm.edu/node/24524 | doi= 10.1093/auk/105.1.142 | access-date= 22 February 2013 | archive-date= 21 October 2020 | archive-url= https://web.archive.org/web/20201021191648/https://sora.unm.edu/node/24524 | url-status= live | url-access= subscription }}</ref><ref name = Stevenson/>

==Distribution and habitat==
[[File:Sterna hirundo - Boat Harbour.jpg|thumb|Non-breeding adult in Australia]]
[[File:Sterna hirundo Hailuoto 20160803 02.jpg|thumb|A pair of juveniles in Marjaniemi, [[Hailuoto]], Finland]]

Most populations of the common tern are strongly migratory, wintering south of their temperate and subarctic Northern Hemisphere breeding ranges. First summer birds usually remain in their wintering quarters, although a few return to breeding colonies some time after the arrival of the adults.<ref name=harrison/> In North America, the common tern breeds along the Atlantic coast from [[Labrador]] to [[North Carolina]], and inland throughout much of Canada east of the [[Rocky Mountains]]. In the United States, some breeding populations can also be found in the states bordering the [[Great Lakes]], and locally on the [[Gulf of Mexico|Gulf]] coast.<ref name=cuthbert4/> There are small, only partially migratory, colonies in the [[Caribbean]]; these are in The Bahamas and Cuba,<ref name=raff>Raffaele et al. (2003) p. 292.</ref> and off Venezuela in the [[Los Roques archipelago|Los Roques]] and [[Las Aves archipelago]]s.<ref name=hilty>Hilty (2002) p. 310.</ref>

New World birds winter along both coasts of Central and South America, to Argentina on the east coast and to northern Chile on the west coast.<ref name=harrison>Harrison (1998) pp. 370–374.</ref><ref name=cuthbert4>Cuthbert (2003) p. 4.</ref> Records from South America and the Azores show that some birds may cross the Atlantic in both directions on their migration.<ref name=lima>Lima (2006) p. 132.</ref><ref name=neves>{{cite journal |last=Neves |first=Verónica C |author2=Bremer, R Esteban |author3=Hays, Helen W |year=2002 |title=Recovery in Punta Rasa, Argentina of Common Terns banded in the Azores archipelago, North Atlantic |journal=Waterbirds |volume=25 |issue=4 |pages=459–461 |url=http://www.horta.uac.pt/intradop/images/stories/perspages/veronicaneves/09_Waterbirds2002.pdf |doi=10.1675/1524-4695(2002)025[0459:RIPRAO]2.0.CO;2 |s2cid=86369861 |access-date=17 February 2012 |archive-date=9 August 2017 |archive-url=https://web.archive.org/web/20170809230052/http://www.horta.uac.pt/intradop/images/stories/perspages/veronicaneves/09_Waterbirds2002.pdf |url-status=live }}</ref>

The common tern breeds across most of Europe, with the highest numbers in the north and east of the continent. There are small populations on the north African coast, and in the [[Azores]], [[Canary Islands]] and [[Madeira]]. Most winter off western or southern Africa, birds from the south and west of Europe tending to stay north of the [[equator]] and other European birds moving further south.<ref name= snow779>Snow & Perrin (1998) pp. 779–782.</ref> The breeding range continues across the temperate and [[taiga]] zones of Asia, with scattered outposts on the [[Persian Gulf]] and the coast of Iran.<ref name=hume39>Hume (1993) pp. 39–41.</ref> Small populations breed on islands off Sri Lanka,<ref name=hoffmann>{{cite journal |author=Hoffmann, Thilo W |year=1990 |title=Breeding of the Common Tern ''Sterna hirundo'' in Sri Lanka |journal=Journal of the Bombay Natural History Society |volume=87 |issue=1 |pages=68–72 |url=https://biodiversitylibrary.org/page/48806758 |access-date=27 December 2017 |archive-date=26 October 2020 |archive-url=https://web.archive.org/web/20201026105813/https://www.biodiversitylibrary.org/page/48806758 |url-status=live }}</ref><ref name=hoffmann2>{{cite journal |author=Hoffmann, Thilo W |year=1992 |title=Confirmation of the breeding of the Common Tern ''Sterna hirundo'' Linn. in Sri Lanka |journal=Journal of the Bombay Natural History Society |volume=89 |issue=2 |pages=251–252 |url=https://biodiversitylibrary.org/page/48732715 |access-date=27 December 2017 |archive-date=3 July 2022 |archive-url=https://web.archive.org/web/20220703024047/https://www.biodiversitylibrary.org/page/48732715 |url-status=live }}</ref> and in the [[Ladakh]] region of the Tibetan plateau.<ref name=ras>Rasmussen & Anderton (2005) pp. 194–195.</ref> Western Asian birds winter in the northern [[Indian Ocean]],<ref name=harrison/><ref>{{Cite journal|last=Khan|first=Asif N.|date=1 April 2015|title=Record of Common Tern ''Sterna hirundo'' from Andaman & Nicobar Islands, India|journal=Journal of the Bombay Natural History Society |volume=112|issue=1|page=30|doi=10.17087/jbnhs/2015/v112i1/92329|doi-access=free}}</ref> and ''S.{{nbs}}h.{{nbs}}tibetana'' appears to be common off [[East Africa]] during the Northern Hemisphere winter.<ref name=Zimmerman>Zimmerman et al. (2010) p. 354.</ref> Birds from further north and east in Asia, such as ''S.{{nbs}}h.{{nbs}}longipennis'', move through Japan, Thailand and the western [[Pacific Ocean|Pacific]] as far as southern Australia.<ref name=harrison/> There are small and erratic colonies in [[West Africa]], in Nigeria and Guinea-Bissau, unusual in that they are within what is mainly a wintering area.<ref name=hume39/> Only a few common terns have been recorded in New Zealand,<ref name=Robertson>Robertson & Heather (2005) p. 126.</ref> and this species' status in [[Polynesia]] is unclear.<ref name=watling170>Watling (2003) pp. 204–205.</ref> A bird [[Bird ringing|ringed]] at the nest in Sweden was found dead on [[Stewart Island]], New Zealand, five months later, having flown an estimated 25,000{{nbs}}km (15,000{{nbs}}mi).<ref name=newton>Newton (2010) pp. 150–151.</ref>

As long-distance migrants, common terns sometimes occur well outside their normal range. Stray birds have been found inland in Africa (Zambia and Malawi), and on the Maldives and Comoros islands;<ref name=BirdLife2>{{cite web |title=BirdLife International Species factsheet: ''Sterna hirundo'', additional information |publisher=BirdLife International |url=http://www.birdlife.org/datazone/speciesfactsheet.php?id=3270&m=1 |access-date=26 January 2012 |archive-date=4 September 2011 |archive-url=https://web.archive.org/web/20110904192654/http://www.birdlife.org/datazone/speciesfactsheet.php?id=3270&m=1 }}</ref> the nominate subspecies has reached Australia,<ref name=Simpson>Simpson & Day (2010) p. 110.</ref> the Andes, and the interior of South America.<ref name=peru/><ref name=Costanzo>{{cite journal |last=DiCostanzo |first=Joseph |year=1978 |title=Occurrences of the Common Tern in the interior of South America |journal=Bird-Banding |volume=49 |issue=3 |pages=248–251 |doi=10.2307/4512366|jstor=4512366}}</ref> Asian ''S.{{nbs}}h.{{nbs}}longipennis'' has recent records from western Europe.<ref name=BW>{{cite journal |last=Darby |first=Chris |year=2011 |title=Eastern Common Terns in Suffolk and Belgium |journal=Birding World |volume=24 |issue=12 |pages=511–512}}</ref>

The common tern breeds over a wider range of habitats than any of its relatives, nesting from the [[taiga]] of Asia to tropical shores,<ref name=hume30>Hume (1993) pp. 30–37.</ref> and at altitudes up to {{convert|2000|m|abbr=on}} in Armenia, and {{convert|4800|m|abbr=on}} in Asia.<ref name=snow779/> It avoids areas which are frequently exposed to excessive rain or wind, and also icy waters, so it does not breed as far north as the Arctic tern. The common tern breeds close to freshwater or the sea on almost any open flat habitat, including sand or [[shingle beach]]es, firm dune areas, [[salt marsh]], or, most commonly, islands. Flat grassland or [[heath]], or even large flat rocks may be suitable in an island environment.<ref name=hume30/> In mixed colonies, common terns will tolerate somewhat longer ground vegetation than Arctic terns, but avoid the even taller growth acceptable to roseate terns; the relevant factor here is the different leg lengths of the three species.<ref name=Fisher/> Common terns adapt readily to artificial floating rafts, and may even nest on flat factory roofs.<ref name=hume30/> Unusual nest sites include hay bales, a stump {{convert|0.6|m|ft|0|abbr=on}} above the water, and floating logs or vegetation. There is a record of a common tern taking over a [[spotted sandpiper]] nest and laying its eggs with those of the [[wader]].<ref name=ontario/> Outside the breeding season, all that is needed in terms of habitat is access to fishing areas, and somewhere to land. In addition to natural beaches and rocks, boats, buoys and piers are often used both as perches and as night-time roosts.<ref name=hume30/>

==Behaviour==
===Territory===
The common tern breeds in colonies which do not normally exceed two thousand [[Breeding pair|pair]]s,<ref name= snow779/> but may occasionally number more than twenty thousand pairs.<ref name= wolf>de Wolf, P. "BioIndicators and the Quality of the Wadden Sea" in Best & Haeck (1984) p. 362.</ref> Colonies inland tend to be smaller than on the coast. Common terns often nest alongside other coastal species, such as Arctic,<ref name=rob>{{cite journal |last=Robinson |first=James A |author2=Chivers, Lorraine S |author3=Hamer, Keith C |year=2001 |title=A comparison of Arctic Tern ''Sterna paradisaea'' and Common Tern ''S. hirundo'' nest-site characteristics on Coquet Island, north-east England |journal=Atlantic Seabirds |volume=3 |issue=2 |pages=49–58 |url=http://www.seabirdgroup.org.uk/journals/as_3_2.pdf |archive-url=https://web.archive.org/web/20140527212407/http://www.seabirdgroup.org.uk/journals/as_3_2.pdf |archive-date=27 May 2014}}</ref> roseate and [[Sandwich tern]]s, [[black-headed gull]]s,<ref name=ramos>{{cite journal |last=Ramos |first=Jaime A |author2=Adrian J |year=1995 |title=Nest-site selection by Roseate Terns and Common Terns in the Azores |journal=Auk |volume=112 |issue=3 |pages=580–589 |url=http://sora.unm.edu/sites/default/files/journals/auk/v112n03/p0580-p0589.pdf |access-date=22 February 2013 |archive-date=28 May 2014 |archive-url=https://web.archive.org/web/20140528005645/http://sora.unm.edu/sites/default/files/journals/auk/v112n03/p0580-p0589.pdf |url-status=live }}</ref><ref name=fuchs>{{cite journal |last=Fuchs |first=Eduard |year=1977 |title=Predation and anti-predator behaviour in a mixed colony of terns ''Sterna'' sp. and Black-Headed Gulls ''Larus ridibundus'' with special reference to the Sandwich Tern ''Sterna sandvicensis'' |journal=Ornis Scandinavica |volume=8 |issue=1 |pages=17–32 |doi=10.2307/3675984|jstor=3675984}}</ref> and [[black skimmer]]s.<ref name=erwin>{{cite journal |last=Erwin |first=Michael R |year=1977 |title=Black Skimmer breeding ecology and behavior |journal=Auk |volume=94 |pages=709–717 |url=http://sora.unm.edu/sites/default/files/journals/auk/v094n04/p0709-p0717.pdf |doi=10.2307/4085267 |issue=4 |jstor=4085267 |access-date=22 February 2013 |archive-date=27 May 2014 |archive-url=https://web.archive.org/web/20140527214231/http://sora.unm.edu/sites/default/files/journals/auk/v094n04/p0709-p0717.pdf |url-status=live }}</ref> Especially in the early part of the breeding season, for no known reason, most or all of the terns will fly in silence low and fast out to sea. This phenomenon is called a "dread".<ref name= snow779/>

On their return to the breeding sites, the terns may loiter for a few days before settling into a territory,<ref name=hume86/> and the actual start of nesting may be linked to a high availability of fish.<ref name=safina>{{cite journal |last=Safina |first=Carl |author2=Burger, Joanna |year=1988 |title=Prey dynamics and the breeding phenology of Common Terns (''Sterna hirundo'') |journal=Auk |volume=105 |issue=4 |pages=720–726 |url=http://sora.unm.edu/sites/default/files/journals/auk/v105n04/p0720-p0726.pdf |doi=10.1093/auk/105.4.720 |access-date=22 February 2013 |archive-date=18 July 2015 |archive-url=https://web.archive.org/web/20150718134823/http://sora.unm.edu/sites/default/files/journals/auk/v105n04/p0720-p0726.pdf |url-status=live }}</ref> Terns defend only a small area, with distances between nests sometimes being as little as {{convert|50|cm|abbr=on}}, although {{convert|150|-|350|cm|abbr=on}} is more typical. As with many birds, the same site is re-used year after year, with a record of one pair returning for 17 successive breeding seasons. Around ninety per cent of experienced birds reuse their former territory, so young birds must nest on the periphery, find a bereaved mate, or move to another colony.<ref name=hume86>Hume (1993) pp. 86–90.</ref> A male selects a nesting territory a few days after his arrival in the spring, and is joined by his previous partner unless she is more than five days late, in which case the pair may separate.<ref name=solis>{{cite journal |last=Gonzalez-Solis |first= J |author2=Becker, P H |author3=Wendeln, H |s2cid= 24145857 |year=1999 |title=Divorce and asynchronous arrival in Common Terns (''Sterna hirundo'') |journal=Animal Behaviour |volume=58 |issue=5 |pages=1123–1129 |doi=10.1006/anbe.1999.1235 |pmid=10564616}}</ref>

Inbreeding among close ''S. hirundo'' relatives appears to be avoided passively by immigration and dispersal rather than by [[kin recognition|kin discrimination]] and [[mate choice]].<ref>Sonja C. Ludwig, Peter H. Becker (2011) Immigration prevents inbreeding in a growing colony of a long-lived and philopatric seabird. Ibis. volume 154, Issue 1, pgs. 74–84. https://doi.org/10.1111/j.1474-919X.2011.01199.x</ref>

The defence of the territory is mainly by the male, who repels intruders of either sex. He gives an alarm call, opens his wings, raises his tail and bows his head to show the black cap. If the intruder persists, the male stops calling and fights by bill grappling until the intruder submits by raising its head to expose the throat. Aerial trespassers are simply attacked, sometimes following a joint upward spiralling flight.<ref name=hume86/> Despite the aggression shown to adults, wandering chicks are usually tolerated, whereas in a gull colony they would be attacked and killed. The nest is defended until the chicks have fledged, and all the adults in the colony will collectively repel potential predators.<ref name=hume79/>

===Breeding===
[[File:Common tern (Sterna hirundo) fledgling Danube delta.jpg|thumb|Fledgling, Danube delta, Romania]]
Pairs are established or confirmed through aerial [[courtship display]]s in which a male and a female fly in wide circles up to {{convert|200|m|abbr=on}} or more, calling all the while, before the two birds descend together in zigzag glides. If the male is carrying a fish, he may attract the attention of other males too. On the ground, the male courts the female by circling her with his tail and neck raised, head pointing down, and wings partially open. If she responds, they may both adopt a posture with the head pointed skywards. The male may tease a female with the fish, not parting with his offering until she has displayed to him sufficiently.<ref name=hume91>Hume (1993) pp. 91–99.</ref> Once courtship is complete, the male makes a shallow depression in the sand, and the female scratches in the same place. Several trials may take place until the pair settle on a site for the actual nest.<ref name=hume91/> The eggs may be laid on bare sand, gravel or soil, but a lining of debris or vegetation is often added if available,<ref name=snow779/> or the nest may be rimmed with seaweed, stones or shells. The saucer-shaped scrape is typically {{convert|4|cm|abbr=on}} deep and {{convert|10|cm|abbr=on}} across, but may extend to as much as {{convert|24|cm|abbr=on}} wide including the surrounding decorative material.<ref name=hume100>Hume (1993) pp. 100–111.</ref> Breeding success in areas prone to flooding has been enhanced by the provision of artificial mats made from [[Zostera|eelgrass]], which encourage the terns to nest in higher, less vulnerable areas, since many prefer the mats to bare sand.<ref name=Palestis>{{cite journal |last=Palestis |first=Brian G |year=2009 |title=Use of artificial eelgrass mats by saltmarsh-nesting Common Terns (''Sterna hirundo'') |journal=In Vivo |volume=30 |issue=3 |pages=11–16 |url=http://aquaticcommons.org/4729/1/eelgrass_mats.pdf |access-date=8 February 2012 |archive-date=27 May 2014 |archive-url=https://web.archive.org/web/20140527215847/http://aquaticcommons.org/4729/1/eelgrass_mats.pdf |url-status=live }}</ref> The common tern tends to use more nest material than roseate or Arctic terns, although roseate often nests in areas with more growing vegetation.<ref name= Lloyd>Lloyd et al. (2010) p. 207.</ref><ref name= Bent>Bent (1921) p. 252.</ref>

Terns are expert at locating their nests in a large colony. Studies show that terns can find and excavate their eggs when they are buried, even if the nest material is removed and the sand smoothed over. They will find a nest placed {{convert|5|m|abbr=on}} from its original site, or even further if it is moved in several stages. Eggs are accepted if reshaped with [[plasticine]] or coloured yellow (but not red or blue). This ability to locate the eggs is an adaptation to life in an unstable, wind-blown and tidal environment.<ref name= Fisher/>

The peak time for egg production is early May, with some birds, particularly first-time breeders, laying later in the month or in June.<ref name=ontario/><ref name=hume100/> The [[Clutch (eggs)|clutch]] size is normally three eggs; larger clutches probably result from two females laying in the same nest. Egg size averages {{convert|41|x|31|mm|abbr=on}}, although each successive egg in a clutch is slightly smaller than the first laid.<ref name=hume100/> The average egg weight is {{convert|20.2|g|abbr=on}}, of which five per cent is shell.<ref name=bto>{{cite web |title=Common Tern ''Sterna hirundo'' (Linnaeus, 1758) |work=BirdFacts |date=16 July 2010 |url=http://blx1.bto.org/birdfacts/results/bob6150.htm |publisher=British Trust for Ornithology (BTO) |access-date=9 February 2012 |archive-date=18 January 2012 |archive-url=https://web.archive.org/web/20120118042434/http://blx1.bto.org/birdfacts/results/bob6150.htm |url-status=live }}</ref> The egg weight depends on how well-fed the female is, as well as on its position in the clutch. The eggs are cream, [[Buff (colour)|buff]], or pale brown, marked with streaks, spots or blotches of black, brown or grey which help to camouflage them.<ref name=hume100/> Incubation is by both sexes, although more often by the female, and lasts 21–22 days,<ref name=bto/> extending to 25{{nbs}}days if there are frequent disturbances at the colony which cause the adults to leave the eggs unattended;<ref name=hume100/> nocturnal predation may lead to incubation taking up to 34{{nbs}}days.<ref name=ontario/> On hot days the incubating parent may fly to water to wet its belly feathers before returning to the eggs, thus affording the eggs some cooling.<ref name=nisbet/> Except when the colony suffers disaster, ninety per cent of the eggs hatch.<ref name=hume112/> The [[precocial]] [[down feather|downy]] chick is yellowish with black or brown markings,<ref name=hume100/> and like the eggs, is similar to the equivalent stage of the Arctic tern.<ref name=pearson121>Hume & Pearson (1993) pp. 121–124.</ref> The chicks [[fledge]] in 22–28 days,<ref name=bto/> usually 25–26.<ref name=snow779/> Fledged juveniles are fed at the nest for about five days, and then accompany the adults on fishing expeditions. The young birds may receive supplementary feeds from the parents until the end of the breeding season, and beyond. Common terns have been recorded feeding their offspring on migration and in the wintering grounds, at least until the adults move further south in about December.<ref name=nisbet/><ref name=hume120>Hume (1993) pp. 120–123.</ref>

Like many terns, this species is very defensive of its nest and young, and will harass humans, dogs, [[muskrat]]s and most [[Diurnality|diurnal]] birds, but unlike the more aggressive Arctic tern, it rarely hits the intruder, usually swerving off at the last moment. Adults can discriminate between individual humans, attacking familiar people more intensely than strangers.<ref name= Burger>{{cite journal |last=Burger |first=Joanna |author2=Shealer, D A |author3=Gochfeld, Michael |year=1993 |title=Defensive aggression in terns: discrimination and response to individual researchers |journal=Aggressive Behavior |volume=19 |issue=4 |pages=303–311 |doi=10.1002/1098-2337(1993)19:4<303::AID-AB2480190406>3.0.CO;2-P}}</ref> Nocturnal predators do not elicit similar attacks;<ref name= hunter>{{cite journal |last=Hunter |first=Rodger A |author2=Morris, Ralph D |year=1976 |title=Nocturnal predation by a Black-Crowned Night Heron at a Common Tern colony |journal=Auk |url=http://sora.unm.edu/node/22862 |volume=93 |issue=3 |pages=629–633 |jstor=4084965 |access-date=22 February 2013 |archive-date=28 May 2014 |archive-url=https://web.archive.org/web/20140528012956/https://sora.unm.edu/node/22862 |url-status=live }}</ref> colonies can be wiped out by rats, and adults desert the colony for up to eight hours when [[great horned owl]]s are present.<ref name= nisbet3>{{cite journal |last=Nisbet |first=Ian C T |author2=Welton, M |year=1984 |title=Seasonal variations in breeding success of Common Terns: consequences of predation |journal=Condor |volume=86 |issue=1 |pages=53–60 |url=http://sora.unm.edu/node/103417 |jstor=1367345 |doi=10.2307/1367345 |access-date=22 February 2013 |archive-date=28 May 2014 |archive-url=https://web.archive.org/web/20140528020412/https://sora.unm.edu/node/103417 |url-status=live |url-access=subscription }}</ref>

Common terns usually breed once a year. Second clutches are possible if the first is lost. Rarely, a second clutch may be laid and incubated while some chicks from the first clutch are still being fed.<ref name= hays>{{cite journal |last=Hays |first=H |year=1984 |title=Common Terns raise young from successive broods |journal=Auk |volume=101 |issue=2 |pages=274–280 |url=http://sora.unm.edu/sites/default/files/journals/auk/v101n02/p0274-p0280.pdf |doi=10.1093/auk/101.2.274 |access-date=22 February 2013 |archive-date=18 July 2015 |archive-url=https://web.archive.org/web/20150718134846/http://sora.unm.edu/sites/default/files/journals/auk/v101n02/p0274-p0280.pdf |url-status=live }}</ref> The first breeding attempt is usually at four years of age, sometimes at three years. The average number of young per pair surviving to fledging can vary from zero in the event of the colony being flooded to over 2.5 in a good year. In North America, productivity was between 1.0 and 2.0 on islands, but less than 1.0 at coastal and inland sites. Birds become more successful at raising chicks with age. This continues throughout their breeding lives, but the biggest increase is in the first five years.<ref name=nisbet/><ref name="pearson121"/> The maximum documented lifespan in the wild is 23{{nbs}}years in North America<ref name=nisbet2>{{cite journal |last=Nisbet |first=Ian C T |author2=Cam, Emmanuelle |year=2002 |title=Test for age-specificity in survival of the Common Tern |journal=Journal of Applied Statistics |volume=29 |issue=1–4 |pages=65–83 |doi=10.1080/02664760120108467|bibcode=2002JApSt..29...65N |s2cid=62816201 }}</ref><ref name=austin2>{{cite journal |last=Austin |first=Oliver L Sr |year=1953 |title=A Common Tern at least 23 years old |journal=Bird-Banding |volume=24 |issue=1 |page=20 |url=http://sora.unm.edu/sites/default/files/journals/jfo/v024n01/p0020-p0020.pdf |access-date=22 February 2013 |archive-date=1 March 2014 |archive-url=https://web.archive.org/web/20140301131214/http://sora.unm.edu/sites/default/files/journals/jfo/v024n01/p0020-p0020.pdf |url-status=live }}</ref> and 33{{nbs}}years in Europe,<ref name=agebi>{{cite web |title=Longevity records for Britain & Ireland in 2010 |work=Online ringing report |url=http://blx1.bto.org/ring/countyrec/results2010/longevity.htm |publisher=British Trust for Ornithology (BTO) |archive-url=https://web.archive.org/web/20120228140407/http://blx1.bto.org/ring/countyrec/results2010/longevity.htm |archive-date=28 February 2012|access-date=11 February 2012}}</ref><ref name=ageeu>{{cite web |title=European Longevity Records |work=Longevity |url=http://www.euring.org/data_and_codes/longevity-voous.htm |publisher=Euring |access-date=11 February 2012 |archive-date=11 May 2015 |archive-url=https://web.archive.org/web/20150511193839/http://www.euring.org/data_and_codes/longevity-voous.htm |url-status=live }}</ref> but twelve years is a more typical lifespan.<ref name=bto/>

<gallery widths="200px" heights="165px">
File:Common Terns nesting.jpg|Nest site, [[Elliston, Newfoundland and Labrador]]
File:Batalla de golondrinas de mar (Sterna hirundo).jpg|Nest in the [[Ebro Delta]], Tarragona, Catalonia, Spain
File:Sterna hirundo MWNH 0472.JPG|Egg, Collection [[Museum Wiesbaden]]
File:Sterna hirundo -nest with three eggs-8.jpg|Three eggs in a nest on [[Great Gull Island]]
File:CommonTern-Chick.jpg|A chick on an island off the coast of Maine
File:Sterna hirundo -hovering to protect nest-8.jpg|Hovering and screaming to deter intruders on [[Great Gull Island]]
File:Sterna hirundo -Massachusetts, USA -juvenile-8.jpg|This autumn juvenile in Massachusetts has a white forehead, having lost the ginger colouration characteristic of younger birds.
</gallery>

===Food and feeding===
[[File:Sterna hirundo -West Bromwich, England -flying-8.jpg|thumb|Flying over a pond in England. The head and bill point down during a search for fish.]]

Like all ''Sterna'' terns, the common tern feeds by plunge-diving for fish, from a height of {{convert|1|-|6|m|ft|abbr=on}}, either in the sea or in freshwater lakes and large rivers. The bird may submerge for a second or so, but to no more than {{convert|50|cm|abbr=on}} below the surface.<ref name=hume55>Hume (1993) pp. 55–67.</ref> When seeking fish, this tern flies head-down and with its bill held vertically.<ref name=Fisher>Fisher & Lockley (1989) pp. 252–260.</ref> It may circle or hover before diving, and then plunges directly into the water, whereas the Arctic tern favours a "stepped-hover" technique,<ref>Beaman et al. (1998) p. 440.</ref> and the roseate tern dives at speed from a greater height, and submerges for longer.<ref name=BB80>{{cite journal |last=Kirkham |first=Ian R |author2=Nisbet, Ian C T |year=1987 |title=Feeding techniques and field identification of Arctic, Common and Roseate Terns |journal=British Birds |volume=80 |issue=2 |pages=41–47}}</ref> The common tern typically forages up to {{convert|5|-|10|km|mi|abbr=on}} away from the breeding colony, sometimes as far as {{convert|15|km|abbr=on}}.<ref name = BirdLife>{{cite web | title = BirdLife International Species factsheet: ''Sterna hirundo'' | publisher = BirdLife International | url = http://www.birdlife.org/datazone/speciesfactsheet.php?id=3270 | access-date = 23 January 2012 | archive-date = 15 October 2016 | archive-url = https://web.archive.org/web/20161015233814/http://www.birdlife.org/datazone/speciesfactsheet.php?id=3270 | url-status = live }}</ref> It will follow schools of fish, and its west African migration route is affected by the location of huge shoals of [[sardine]]s off the coast of Ghana;<ref name=hume55/> it will also track groups of [[predatory fish]] or [[dolphin]]s, waiting for their prey to be driven to the sea's surface.<ref name = BirdLife/><ref name=bugoni>{{cite journal |last=Bugoni |first=Leandro |author2=Vooren, Carolus Maria |year=2004 |title=Feeding ecology of the Common Tern ''Sterna hirundo'' in a wintering area in southern Brazil |journal=Ibis |volume=146 |issue=3 |pages=438–453 |doi=10.1111/j.1474-919X.2004.00277.x}}</ref> Terns often feed in flocks, especially if food is plentiful, and the fishing success rate in a flock is typically about one-third higher than for individuals.<ref name=hume55/>

Terns have red oil droplets in the [[cone cell]]s of the [[retina]]s of their eyes. This improves contrast and sharpens distance [[Bird vision|vision]], especially in hazy conditions.<ref name=Sinclair>Sinclair (1985) pp. 93–95.</ref> Birds that have to see through an air/water interface, such as terns and gulls, have more strongly coloured [[carotenoid]] [[pigment]]s in the cone oil drops than other avian species.<ref name=Varela>Varela, F J; Palacios, A G; Goldsmith T M (1993) "Vision, Brain, and Behavior in Birds" in Zeigler & Bischof (1993) pp. 77–94.</ref> The improved eyesight helps terns to locate shoals of fish, although it is uncertain whether they are sighting the [[phytoplankton]] on which the fish feed, or observing other terns diving for food.<ref name=Lythgoe>Lythgoe (1979) pp. 180–183.</ref> Tern's eyes are not particularly [[ultraviolet]] sensitive, an adaptation more suited to terrestrial feeders like the gulls.<ref name=Hastad>{{cite journal |last=Håstad |first=Olle |author2=Ernstdotter, Emma |author3=Ödeen, Anders |title=Ultraviolet vision and foraging in dip and plunge diving birds |journal=Biology Letters |volume=1 |issue=3 |pages=306–309 |year=2005 |pmid=17148194 |doi=10.1098/rsbl.2005.0320 |pmc=1617148}}</ref>
[[File:Sterna hirundo -Nantucket National Wildlife Refuge, Massachusetts, USA -adult and juvenile-8.jpg|thumb|An adult bringing a [[sand eel]] to a juvenile at [[Nantucket National Wildlife Refuge]]]]

The common tern preferentially hunts fish {{convert|5|-|15|cm|in|abbr=on}} long.<ref name=ontario>Sandilands (2005) pp. 157–160.</ref><ref name=hume55/> The species caught depend on what is available, but if there is a choice, terns feeding several chicks will take larger prey than those with smaller broods.<ref name= Stephens>Stephens et al. (2007) p. 295.</ref> The proportion of fish fed to chicks may be as high as ninety-five per cent in some areas, but [[invertebrate]] prey may form a significant part of the diet elsewhere. This may include [[Annelid|worm]]s, [[leech]]es, [[Mollusca|mollusc]]s such as small [[squid]], and [[crustacean]]s ([[prawn]]s, [[shrimp]] and [[Hippoidea|mole crabs]]). In freshwater areas, large [[insect]]s may be caught, such as [[beetle]]s, [[cockchafer]]s and [[moth]]s. Adult insects may be caught in the air, and [[larva]]e picked from the ground or from the water surface. Prey is caught in the bill and either swallowed head-first, or carried back to the chicks. Occasionally, two or more small fish may be carried simultaneously.<ref name=hume55/> When adults take food back to the nest, they recognise their young by call, rather than visual identification.<ref name=Stevenson>{{cite journal |last=Stevenson |first=J G |author2=Hutchison, R E |author3=Hutchison, J B |author4=Bertram B C R |author5= Thorpe, W H |year=1970 |title=Individual recognition by auditory cues in the Common Tern (''Sterna hirundo'') |journal=Nature |volume=226 |issue=5245 |pages=562–563 |doi=10.1038/226562a0 |pmid=16057385|bibcode=1970Natur.226..562S|s2cid=4181980 }}</ref>

The common tern may attempt to steal fish from Arctic terns,<ref name=hopkins>{{cite journal |last=Hopkins |first=C D |author2=Wiley, R H |year=1972 |title=Food parasitism and competition in two terns |journal=Auk |volume=89 |pages=583–594 |url=http://sora.unm.edu/sites/default/files/journals/auk/v089n03/p0583-p0594.pdf |access-date=22 February 2013 |archive-date=21 April 2014 |archive-url=https://web.archive.org/web/20140421102806/http://sora.unm.edu/sites/default/files/journals/auk/v089n03/p0583-p0594.pdf |url-status=live }}</ref> but might itself be harassed by [[kleptoparasitism|kleptoparasitic]] skuas,<ref name=belisle>{{cite journal |last=Bélisle |first=M |year=1998 |title=Foraging group size: models and a test with jaegers kleptoparasitizing terns |journal=Ecology |volume=79 |issue=6 |pages=1922–1938 |url=http://spectrum.library.concordia.ca/6255/1/MM18374.pdf |doi=10.2307/176699 |jstor=176699 |bibcode=1998Ecol...79.1922B |access-date=16 March 2012 |archive-date=21 April 2014 |archive-url=https://web.archive.org/web/20140421050645/http://spectrum.library.concordia.ca/6255/1/MM18374.pdf |url-status=live }}</ref> [[laughing gull]]s,<ref name=hatch>{{cite journal |last=Hatch |first=J J |year=1975 |title=Piracy by laughing gulls ''Larus atricilla'': an example of the selfish group |journal=Ibis |volume=117 |issue=3 |pages=357–365 |doi=10.1111/j.1474-919X.1975.tb04222.x}}</ref> roseate terns,<ref name=dunn>{{cite journal |last=Dunn |first=E K |year=1973 |title=Robbing behavior of Roseate Terns |journal=Auk |url=http://sora.unm.edu/node/22405 |volume=90 |pages=641–651 |jstor=4084163 |doi=10.2307/4084163 |issue=3 |access-date=22 February 2013 |archive-date=21 April 2014 |archive-url=https://web.archive.org/web/20140421151548/https://sora.unm.edu/node/22405 |url-status=live |doi-access=free |url-access=subscription }}</ref> or by other common terns while bringing fish back to its nest.<ref name=hopkins/> In one study, two males whose mates had died spent much time stealing food from neighbouring broods.<ref name=wilson>{{cite journal |last=Nisbet |first=Ian C T |author2=Wilson, Karen J |author3=Broad, William A |year=1978 |title=Common Terns raise young after death of their mates |journal=The Condor |url=http://sora.unm.edu/node/102828 |volume=80 |issue=1 |pages=106–109 |doi=10.2307/1367802 |jstor=1367802 |access-date=22 February 2013 |archive-date=21 April 2014 |archive-url=https://web.archive.org/web/20140421132515/https://sora.unm.edu/node/102828 |url-status=live |url-access=subscription }}</ref>

Terns normally drink in flight, usually taking seawater in preference to freshwater, if both are available.<ref name=nisbet/> Chicks do not drink before fledging, reabsorbing water, and, like adults, excreting excess salt in a concentrated solution from a specialised nasal gland.<ref name= hughes>{{cite journal |last=Hughes |first=M R |year=1968 |title=Renal and extrarenal sodium excretion in the Common Tern ''Sterna hirundo'' |journal=Physiological Zoology |volume=41 |issue=2 |pages=210–219 |jstor=30155452|doi=10.1086/physzool.41.2.30155452|s2cid=87163637 }}</ref><ref name=Karleskint>Karleskint (2009) p. 317.</ref> Fish bones and the hard [[exoskeleton]]s of crustaceans or insects are regurgitated as [[pellet (ornithology)|pellets]]. Adults fly off the nest to [[Defecation|defecate]], and even small chicks walk a short distance from the scrape to deposit their [[Feces|faeces]]. Adults attacking animals (including humans) will often defecate as they dive, often successfully fouling the intruder.<ref name=nisbet/>

==Predators and parasites==
Rats will take tern eggs, and may even store large numbers in [[Hoarding (animal behavior)|caches]],<ref name=austin1>{{cite journal |last=Austin |first=O L |year=1948 |title=Predation by the common rat (''Rattus norvegicus'') in the Cape Cod colonies of nesting terns |journal=Bird-Banding |volume=19 |issue=2 |pages=60–65 |doi=10.2307/4510014|jstor=4510014}}</ref> and the [[American mink]] is an important predator of hatched chicks, both in North America, and in [[Scotland]] where it has been [[Introduced species|introduce]]d.<ref name=hume112>Hume (1993) pp. 112–119.</ref> The [[red fox]] can also be a local problem.<ref name= jncc/> Because common terns nest on islands, the most common predators are normally other birds rather than mammals. The [[ruddy turnstone]] will take eggs from unattended nests,<ref name=parkes>{{cite journal |last=Parkes |first=K C |author2=Poole, A |author3=Lapham, H |year=1971 |title=The Ruddy Turnstone as an egg predator |journal=Wilson Bulletin |volume=83 |pages=306–307 |url=http://sora.unm.edu/sites/default/files/journals/wilson/v083n03/p0306-p0308.pdf |access-date=22 February 2013 |archive-date=27 May 2014 |archive-url=https://web.archive.org/web/20140527212553/http://sora.unm.edu/sites/default/files/journals/wilson/v083n03/p0306-p0308.pdf |url-status=live }}</ref><ref name=fara>{{cite journal |last=Farraway |first=A |author2=Thomas, K |author3=Blokpoel, H |year=1986 |title=Common Tern egg predation by Ruddy Turnstones |journal=Condor |url=http://sora.unm.edu/node/103749 |volume=88 |issue=4 |pages=521–522 |doi=10.2307/1368282 |jstor=1368282 |access-date=22 February 2013 |archive-date=21 October 2020 |archive-url=https://web.archive.org/web/20201021191356/https://sora.unm.edu/node/103749 |url-status=live |url-access=subscription }}</ref> and gulls may take chicks.<ref name=houde>{{cite journal |last=Houde |first=P |year=1977 |title=Gull-tern interactions on Hicks Island |journal=Proceedings of the Linnaean Society of New York |volume=73 |pages=58–64}}</ref><ref name=whittam>{{cite journal |last=Whittam |first=R M |author2=Leonard, M L |year=2000 |title=Characteristics of predators and offspring influence on nest defense by Arctic and Common Terns |journal=Condor |url=http://sora.unm.edu/node/105635 |volume=102 |issue=2 |pages=301–306 |doi=10.1650/0010-5422(2000)102[0301:COPAOI]2.0.CO;2 |s2cid=56440470 |access-date=22 February 2013 |archive-date=21 October 2020 |archive-url=https://web.archive.org/web/20201021193142/https://sora.unm.edu/node/105635 |url-status=live |url-access=subscription }}</ref> Great horned owls and [[short-eared owl]]s will kill both adults and chicks, and [[black-crowned night heron]]s will also eat small chicks.<ref name=nisbet>{{cite web |author=Nisbet, Ian C |title=Common Tern (''Sterna hirundo'') |url=http://bna.birds.cornell.edu/bna/species/618/articles/introduction |url-access=subscription |publisher=Cornell Lab of Ornithology |access-date=25 January 2012 |archive-date=7 September 2011 |archive-url=https://web.archive.org/web/20110907090302/http://bna.birds.cornell.edu/bna/species/618/articles/introduction}}</ref><ref name=morris>{{cite journal |last=Morris |first=R D |author2=Wiggins, D A |year=1986 |title=Ruddy Turnstones, Great Horned Owls, and egg loss from Common Tern clutches |journal=Wilson Bulletin |volume=98 |pages=101–109 |url=http://sora.unm.edu/sites/default/files/journals/wilson/v098n01/p0101-p0109.pdf |access-date=22 February 2013 |archive-date=18 July 2015 |archive-url=https://web.archive.org/web/20150718135042/http://sora.unm.edu/sites/default/files/journals/wilson/v098n01/p0101-p0109.pdf |url-status=live }}</ref> [[Merlin (bird)|Merlins]] and [[peregrine falcon]]s may attack flying terns; as with other birds, it seems likely that one advantage of flocking behaviour is to confuse fast-flying predators.<ref name=hume79>Hume (1993) pp. 79–85.</ref>

The common tern hosts [[Bird louse|feather lice]], which are quite different from those found in Arctic terns, despite the close relationship of the two birds.<ref name=Rothschild135>Rothschild & Clay (1953 ) p. 135.</ref> It may also be infected by parasitic worms, such as the widespread ''[[Diphyllobothrium]]'' species, the duck parasite ''[[Ligula intestinalis]]'', and ''[[Schistocephalus]]'' species carried initially by fish. [[Cestoda|Tapeworms]] of the family [[Cyclophyllidea]] may also infect this species. The [[mite]] ''[[Reighardia sternae]]'' has been found in common terns from Italy, North America and China.<ref name=Rothschild194>Rothschild & Clay (1953) pp. 194–197.</ref> A study of 75 breeding common terns found that none carried blood parasites.<ref name=Fiorello>{{cite journal |last=Fiorello |first=Christine V |author2=Nisbet, Ian C T |author3=Hatch, Jeremy J |author4=Corsiglia, Carolyn |author5= Pokras, Mark A |year=2009 |title=Hematology and absence of hemoparasites in breeding Common Terns (''Sterna hirundo'') from Cape Cod, Massachusetts |journal=Journal of Zoo and Wildlife Medicine |volume=40 |issue=3 |pages=409–413 |doi=10.1638/2006-0067.1 |pmid=19746853|s2cid=24882069 }}</ref> Colonies have been affected by [[Fowl cholera|avian cholera]] and [[Psittacosis|ornithosis]],<ref name=nisbet/> and it is possible that the common tern may be threatened in the future by outbreaks of [[avian influenza]] to which it is susceptible.<ref name = BirdLife/> In 1961 the common tern was the first wild bird species identified as infected with avian influenza, the [[Influenza A virus subtype H5N3|H5N3]] variant being found in an outbreak of South African birds.<ref name=olsen2006>{{cite journal |last=Olsen |first=Björn |author2=Munster, Vincent J |author3=Wallensten, Anders |author4=Waldenström, Jonas |author5=Osterhaus, D M E |author6= Fouchier, Ron A M |year=2006 |title=Global patterns of influenza A virus in wild birds |journal=Science |volume=312 |issue=5772 |pages=384–388 |doi=10.1126/science.1122438 |pmid=16627734|citeseerx=10.1.1.177.8707 |bibcode=2006Sci...312..384O|s2cid=7795090 }}</ref>

==Status==
[[File:Common Tern96.ogg|thumb|Dark-billed Asian subspecies ''S.{{nbs}}h.{{nbs}}longipennis'' in [[Mooloolaba, Queensland|Mooloolaba]], Australia]]

The common tern is classed as [[least concern]] on the [[IUCN Red List]].<ref name="iucn status 12 November 2021" /> It has a large population of 1.6 to 3.3{{nbs}}million mature individuals and a huge breeding range estimated at {{convert|84300000|km2|abbr=on}}. Breeding numbers have been estimated at a quarter to half a million pairs, the majority breeding in Asia. About 140 thousand pairs breed in Europe.<ref name=Enticott>Enticott (2002) p. 194.</ref> Fewer than eighty thousand pairs breed in North America, with most breeding on the northeast Atlantic coast<ref name=kress>{{cite journal |author=Kress, Stephen W |author2=Weinstein, Evelyn H |author3=Nisbet, Ian C T |author4=Shugart, Gary W |author5=Scharf, William C |author6=Blokpoel, Hans |author7=Smith, Gerald A |author8=Karwowski, Kenneth |author9=Maxwell, George R |author10=Chapdelaine, Gilles |author11=Montevecchi, William A |author12=Lock, Anthony R |author13=Smith, Carol F |author14=Miller, Eileen |author15=Spendelow, Jeffrey A |author16=Gochfeld, Michael |author17=Burger, Joanna |author18=Erwin, R Michael |year=1983 |title=The status of tern populations in northeastern United States and adjacent Canada |journal=Colonial Waterbirds |volume=6 |pages=84–106 |doi=10.2307/1520976|jstor=1520976}}</ref> and a declining population of less than ten thousand pairs breeding in the [[Great Lakes region]].<ref name=cuthbert1>Cuthbert (2003) p. 1.</ref>

In the nineteenth century, the use of tern feathers and wings in the [[Hatmaking|milliner]]y trade was the main cause of large reductions in common tern populations in both Europe and North America, especially on the Atlantic coasts and inland. Sometimes entire stuffed birds were used to make hats. Numbers largely recovered early in the twentieth century mainly due to legislation and the work of [[Conservation movement|conservation]] organizations.<ref name=nisbet/><ref name=jncc>{{cite web |title=Common Tern ''Sterna hirundo'' |work=Latest population trends |url=http://jncc.defra.gov.uk/page-2895 |publisher=Joint Nature Conservation Committee, (JNCC) |access-date=25 January 2012 |archive-date=7 March 2012 |archive-url=https://web.archive.org/web/20120307011220/http://jncc.defra.gov.uk/page-2895 |url-status=live }}</ref> Although some Eurasian populations are stable, numbers in North America have fallen by more than seventy per cent in the last forty years, and there is an overall negative trend in the global estimates for this species.<ref name = BirdLife/>

Threats come from habitat loss through building, pollution or vegetation growth, or disturbance of breeding birds by humans, vehicles, boats or dogs. Local natural flooding may lead to nest losses, and some colonies are vulnerable to predation by rats and large gulls. Gulls also compete with terns for nest sites. Some birds are hunted in the [[Caribbean]] for commercial sale as food.<ref name = BirdLife/> Breeding success may be enhanced by the use of floating nest rafts, manmade islands or other artificial nest sites, and by preventing human disturbance. Overgrown vegetation may be burned to clear the ground, and gulls can be killed or discouraged by deliberate disturbance.<ref name = BirdLife/> Contamination with [[polychlorinated biphenyl]]s (PCBs) resulted in enhanced levels of [[Feminization (biology)|feminisation]] in male embryos, which seemed to disappear prior to fledging, with no effect on colony productivity,<ref name=hart>{{cite journal |last=Hart |first=Constance A |author2=Nisbet, Ian C T |author3=Kennedy, Sean W |author4=Hahn, Mark E |year=2003 |title=Gonadal feminization and halogenated environmental contaminants in Common Terns (''Sterna hirundo''): evidence that ovotestes in male embryos do not persist to the prefledgling stage |journal=Ecotoxicology |volume=12 |issue=1–4 |pages=125–140 |url=http://www.whoi.edu/science/B/people/mhahn/Hart_Ecotox_proofs.pdf |doi=10.1023/A:1022505424074 |pmid=12739862 |bibcode=2003Ecotx..12..125H |s2cid=21308753 |access-date=19 February 2012 |archive-date=21 July 2012 |archive-url=https://web.archive.org/web/20120721023432/http://www.whoi.edu/science/B/people/mhahn/Hart_Ecotox_proofs.pdf |url-status=live }}</ref> but [[dichlorodiphenyldichloroethylene]] (DDE), which results from the breakdown of [[DDT]], led to very low levels of successful breeding in some US locations.<ref name=nisbet/>

The common tern is one of the species to which the [[Agreement on the Conservation of African-Eurasian Migratory Waterbirds]] (AEWA) and the US–Canada [[Migratory Bird Treaty Act of 1918]] apply.<ref name=AEWA>{{cite web|title=Annex 2: Waterbird species to which the Agreement applies |work=Agreement on the conservation of African-Eurasian migratory Waterbirds (AEWA) |url=http://www.unep-aewa.org/documents/agreement_text/eng/pdf/aewa_agreement_text_annex2.pdf |publisher=UNEP/ AEWA Secretariat |access-date=25 January 2012 |archive-url=https://web.archive.org/web/20110728144028/http://www.unep-aewa.org/documents/agreement_text/eng/pdf/aewa_agreement_text_annex2.pdf |archive-date=28 July 2011}}</ref><ref name=1918treaty>{{cite web |title=List of Migratory Birds |work=Birds protected by the Migratory Bird Treaty Act |url=http://www.fws.gov/migratorybirds/RegulationsPolicies/mbta/mbtandx.html |publisher=US Fish and Wildlife Service |access-date=25 January 2012 |archive-date=7 June 2019 |archive-url=https://web.archive.org/web/20190607221124/https://www.fws.gov/migratorybirds/RegulationsPolicies/mbta/mbtandx.html |url-status=live }}</ref> Parties to the AEWA agreement are required to engage in a wide range of conservation strategies described in a detailed action plan. The plan is intended to address key issues such as species and habitat conservation, management of human activities, research, education, and implementation.<ref name=AEWAintro>{{cite web|title=Introduction |work=African-Eurasian Waterbird Agreement |url=http://www.unep-aewa.org/about/introduction.htm |publisher=UNEP/ AEWA Secretariat |access-date=25 January 2012 |archive-url=https://web.archive.org/web/20120211082252/http://www.unep-aewa.org/about/introduction.htm |archive-date=11 February 2012}}</ref> The North American legislation is similar, although there is a greater emphasis on protection.<ref name=law>{{cite web |title=Migratory Bird Treaty Act of 1918 |work=Digest of Federal Resource Laws of Interest to the U. S. Fish and Wildlife Service |url=http://www.fws.gov/laws/lawsdigest/migtrea.html |publisher=U. S. Fish and Wildlife Service |access-date=25 January 2012 |archive-date=14 January 2012 |archive-url=https://web.archive.org/web/20120114090828/http://www.fws.gov/laws/lawsdigest/migtrea.html |url-status=live }}</ref>

==See also==
* [[Lake Bant tern colony]]

== Citations ==
{{Reflist|35em}}

==Cited texts==
* {{cite book | last = Beaman | first = Mark |author2=Madge, Steve|author3=Burn, Hilary|author4=Zetterstrom, Dan | title = The Handbook of Bird Identification: For Europe and the Western Palearctic | year = 1998 | location = London | publisher = Christopher Helm | isbn = 0-7136-3960-1}}
* {{cite book | last = Bent | first = Arthur Cleveland | title = Life Histories of North American Gulls and Terns: Order Longipennes | url = https://archive.org/details/cu31924022523868 | year = 1921 | location = Washington, DC | publisher = Government Printing Office}}
* {{cite book | last = Best | first = E P H|author2=Haeck, J | title =Ecological Indicators for the Assessment of the Quality of Air, Water, Soil and Ecosystems: Symposium Papers ("Environmental Monitoring & Assessment") | year = 1984 | location = Dordrecht | publisher = D Reidel | isbn =90-277-1708-7}}
* {{cite book | last = Blomdahl | first = Anders |author2=Breife, Bertil|author3=Holmstrom, Niklas | title = Flight Identification of European Seabirds | year = 2007| location = London | publisher = Christopher Helm | isbn = 978-0-7136-8616-6}}
* {{cite book | last = Brazil | first = Mark | title = Birds of East Asia | year = 2008 | location = London | publisher = Christopher Helm | isbn = 978-0-7136-7040-0}}
* {{cite book | last1 = Cocker | first1 = Mark | last2= Mabey |first2 = Richard |title = Birds Britannica | year = 2005 | location = London | publisher = Chatto & Windus | isbn = 0-7011-6907-9}}
* {{cite book | last = Cuthbert | first = Francesca J | author2 = Wires, Linda R | author3 = Timmerman, Kristina | title = Status Assessment and Conservation Recommendations for the Common Tern (''Sterna hirundo'') in the Great Lakes Region | year = 2003 | publisher = U S Department of the Interior, Fish and Wildlife Service, Fort Snelling, Minnesota | url = http://www.fws.gov/midwest/eco_serv/soc/birds/pdf/cote-sa03.pdf | archive-url = https://web.archive.org/web/20141127170958/http://www.fws.gov/midwest/eco_serv/soc/birds/pdf/cote-sa03.pdf | archive-date =27 November 2014}}
* {{cite book | last = van Duivendijk | first = Nils | title = Advanced Bird ID Handbook: The Western Palearctic | year =2011 | location = London | publisher = New Holland | isbn =978-1-78009-022-1}}
* {{cite book | last = Enticott | first = Jim |author2=Tipling, David | title = Seabirds of the World | year =2002 | location = London | publisher = New Holland Publishers | isbn = 1-84330-327-2}}
* {{cite book| last = Fisher | first = James |author2=Lockley, R M | title = Sea‑Birds (Collins New Naturalist series) | year = 1989 | publisher = Bloomsbury Books |location = London | isbn =1-870630-88-2}}
* {{cite book | last = Grimmett | first = Richard |author2=Inskipp, Carol|author3=Inskipp, Tim| title = Pocket Guide to Birds of the Indian Subcontinent | publisher = Christopher Helm |year = 2002| location = London | isbn = 0-7136-6304-9}}
* {{cite book| last = Harrison | first = Peter | title = Seabirds | year = 1988 | publisher = Christopher Helm|location = London | isbn = 0-7470-1410-8}}
* {{cite book | last = Hilty | first = Steven L | title = Birds of Venezuela | year =2002 | location = London | publisher = Christopher Helm | isbn =0-7136-6418-5}}
* {{cite book | last = Hume | first = Rob | title = The Common Tern | year = 1993 | location = London | publisher = Hamlyn | isbn = 0-540-01266-1}}
* {{cite book | last = Hume | first = Rob |author2=Pearson, Bruce | title =Seabirds | year =1993 | location = London | publisher = Hamlyn | isbn =0-600-57951-4}}
* {{cite book | last = Karleskint | first =George |author2=Turner, Richard |author3=Small, James | title = Introduction to Marine Biology| year =2009 | location = Florence, Kentucky | publisher = Brooks/Cole | isbn = 978-0-495-56197-2}}
* {{cite book | last = Lima | first = Pedro | title = Aves do litoral norte da Bahia | year = 2006 | location = Bahia | publisher = Atualidades Ornitológicas | language = pt, en | url = http://www.ao.com.br/download/lnbahia.pdf | access-date = 2012-02-17 | archive-date = 2015-09-23 | archive-url = https://web.archive.org/web/20150923172630/http://www.ao.com.br/download/lnbahia.pdf }}
* {{cite book | last = Linnaeus | first = C | author-link = Carl Linnaeus | title = Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata | location = Stockholm |publisher = Laurentii Salvii | year=1758 | language = la}}
* {{cite book | last = Lloyd | first = Clare |author2=Tasker, Mark L|author3=Partridge, Ken | title = The Status of Seabirds in Britain and Ireland | year =2010 | location = London | publisher = Poyser | isbn = 978-1-4081-3800-7}}
* {{cite book| last = Lythgoe | first = J N| title =The Ecology of Vision | year =1979 | publisher =Clarendon Press |location = Oxford | isbn = 0-19-854529-0 }}
* {{cite book| last = Newton | first = Ian | title = Bird Migration | year = 2010 | publisher = Collins |location = London| isbn = 978-0-00-730731-9}}
* {{cite book| last = Olsen | first = Klaus Malling |author2=Larsson, Hans | title = Terns of Europe and North America | year =1995 | publisher = Christopher Helm |location = London| isbn =0-7136-4056-1}}
* {{cite book | last = Raffaele | first = Herbert A |author2=Raffaele, Janis I|author3=Wiley, James|author4=Garrido, Orlando H|author5=Keith, Allan R | title = Field Guide to the Birds of the West Indies | year = 2003 | location = London | publisher = Christopher Helm | isbn = 0-7136-5419-8}}
* {{cite book|author1=Rasmussen, Pamela C |author2=Anderton, John C |year=2005| title=Birds of South Asia. The Ripley Guide. Volume 2 | publisher=Smithsonian Institution and Lynx Edicions | place= Washington DC and Barcelona | isbn = 84-87334-67-9}}
* {{cite book | last = Robertson | first = Hugh |author2=Heather, Barrie | title = The Field Guide to the Birds of New Zealand | year = 2005 | location = Auckland | publisher = Penguin Group (NZ)| isbn =0-14-302040-4}}
* {{cite book |title= Fleas, Flukes and Cuckoos. A Study of Bird Parasites |author= Rothschild, Miriam |author-link= Miriam Rothschild |author2= Clay, Theresa |year= 1953 |publisher= Collins |location= London}}
* {{cite book | last =Sandilands | first = Allan P | title = Birds of Ontario: Habitat Requirements, Limiting Factors, and Status Nonpasserines, Waterfowl Through Cranes: 1 | year =2005 | location = Vancouver | publisher = University of British Columbia Press | isbn =0-7748-1066-1}}
* {{cite book | last = Schulenberg | first = Thomas S |author2=Stotz, Douglas F|author3=Lane, Daniel F|author4=O'Neill, John P|author5=Parker, Theodore A | title = Birds of Peru | year = 2010| location = Princeton, New Jersey | publisher = Princeton University Press | isbn =978-0-691-13023-1}}
* {{cite book | last = Simpson | first = Ken |author2=Day, Nicolas | title = Field Guide to the Birds of Australia | edition = 8th | year = 2010| location = Camberwell, Victoria | publisher = Penguin Books | isbn =978-0-670-07231-6}}
* {{cite book | last = Sinclair | first =Ian |author2=Hockey, Phil |author3=Tarboton, Warwick |title = SASOL Birds of Southern Africa | year = 2002 | publisher = Struik | isbn = 1-86872-721-1 |location = Cape Town}}
* {{cite book| last = Sinclair | first = Sandra | title = How Animals See: Other Visions of Our World | year = 1985| publisher =Croom Helm |location = Beckenham, Kent | isbn =0-7099-3336-3 }}
* {{cite book | editor1-last = Snow | editor1-first = David |editor2-last=Perrins|editor2-first=Christopher M| title = The Birds of the Western Palearctic (BWP) |edition=(2 volume) Concise | publisher = Oxford University Press | year = 1998| location = Oxford | isbn = 0-19-854099-X}}
* {{cite book | last = Stephens | first = David W |author2=Brown, Joel Steven|author3=Ydenberg, Ronald C | title = Foraging: Behavior and Ecology | year =2007 | location = Chicago | publisher = University of Chicago Press | isbn = 978-0-226-77264-6}}
* {{cite book | last = Vinicombe | first = Keith |author2=Tucker, Laurel|author3=Harris, Alan | title = The Macmillan Field Guide to Bird Identification | year = 1990 | location = London | publisher = Macmillan | isbn =0-333-42773-4}}
* {{cite book| last = Wassink | first = Jan L |author2=Ort, Kathleen | title = Birds of the Pacific Northwest Mountains: The Cascade Range, the Olympic Mountains, Vancouver Island, and the Coast Mountains | year =1995 | location = Missoula, Montana | publisher = Mountain Press | isbn =0-87842-308-7}}
* {{cite book | last = Watling | first = Dick | title = A Guide to the Birds of Fiji and Western Polynesia | year = 2003 | location = Suva, Fiji | publisher = Environmental Consultants | isbn =982-9030-04-0}}
* {{cite book | last= Zeigler | first = Harris Philip|author2=Bischof, Hans-Joachim | title = Vision, Brain, and Behavior in Birds: A Comparative Review| year = 1993 |location = Cambridge, Massachusetts| publisher = MIT Press| isbn = 0-262-24036-X}}
* {{cite book | last = Zimmerman | first = Dale A |author2=Pearson, David J|author3=Turner, Donald A | title = Birds of Kenya and Northern Tanzania| year = 2010 | location = London | publisher = Christopher Helm| isbn = 978-0-7136-7550-4}}

==External links==
{{Commons category|Sterna hirundo|common tern}}
{{Wikispecies|Sterna hirundo}}
* Common tern – [http://sabap2.adu.org.za/docs/sabap1/327.pdf Species text in The Atlas of Southern African Birds]
* {{InternetBirdCollection|common-tern-sterna-hirundo|Common tern}}
* [http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Common_Tern.html Common Tern Species Account] – Cornell Lab of Ornithology
* [https://web.archive.org/web/20090507030712/http://www.mbr-pwrc.usgs.gov/id/framlst/i0700id.html Common tern – ''Sterna hirundo''] – USGS Patuxent Bird Identification InfoCenter
* [http://www.madeirabirds.com/common_tern Common Tern Profile] – Madeira Wind Birds
* {{VIREO|common+tern|Common tern}}

{{Portal bar|Animals|Biology|Birds}}
{{Taxonbar |from=Q18875}}
{{Authority control}}

[[Category:Articles containing video clips]]
[[Category:Birds described in 1758]]
[[Category:Birds of the Dominican Republic]]
[[Category:Holarctic birds]]
[[Category:Sterna]]
[[Category:Taxa named by Carl Linnaeus]]