Editing Arctic tern (section)

== Distribution and migration ==
The Arctic tern has a continuous worldwide circumpolar breeding distribution; there are no recognized [[subspecies]]. It can be found in coastal regions in cooler temperate parts of [[North America]] and [[Palearctic|Eurasia]] during the [[northern hemisphere|northern]] summer. During the [[southern hemisphere|southern]] summer, it can be found at sea, reaching the northern edge of the Antarctic ice.<ref name="RSPB"/>

The Arctic tern is famous for its migration; it flies from its Arctic breeding grounds to the Antarctic and back again each year. The shortest distance between these areas is {{convert|19000|km|abbr=on}}. The long journey ensures that this bird sees two summers per year and more daylight than any other creature on the planet.<ref name="Cramp"/> One example of this bird's remarkable long-distance flying abilities involves an Arctic tern [[bird ringing|ringed]] as an unfledged chick on the [[Farne Islands]], [[Northumberland]], UK, in the northern summer of 1982 that reached [[Melbourne]], Australia in October, just three months after fledging – a journey of more than {{convert|22000|km|abbr=on}}.<ref name="Heavisides et al."/> Another example is that of a chick ringed in [[Labrador]], [[Canada]], on 23 July 1928. It was found in South Africa four months later.<ref name="Birds of Nova Scotia"/>

A 2010 study using tracking devices attached to the birds showed that the above examples are not unusual for the species. In fact, the study showed that previous research had seriously underestimated the annual distances travelled by the Arctic tern. Eleven birds that bred in Greenland or Iceland covered {{convert|70900|km|abbr=on}} on average in a year, with a maximum of {{convert|81600|km|abbr=on}}.<ref>{{cite journal |last1=Egevang |first1=Carsten |last2=Stenhouse |first2=Iain J. |last3=Phillips |first3=Richard A. |last4=Petersen |first4=Aevar |last5=Fox |first5=James W. |last6=Silk |first6=Janet R. D. |year=2010 |title=Tracking of Arctic terns ''Sterna paradisaea'' reveals longest animal migration |journal=Proceedings of the National Academy of Sciences |volume=107 |issue=5 |pages=2078–2081 |doi=10.1073/pnas.0909493107 |doi-access=free |pmid=20080662 |pmc=2836663 |bibcode=2010PNAS..107.2078E }}</ref> The difference from previous estimates is due to the birds taking meandering courses rather than following a straight route as was previously assumed. The birds follow a somewhat convoluted course in order to take advantage of prevailing winds.<ref name="Arctic terns' flying feat"/> The average Arctic tern lives about 30 years and will, based on the above research, travel some {{convert|2.4|e6km|abbr=unit}} during its lifetime, the equivalent of a roundtrip from Earth to the Moon more than three times.<ref>{{cite web|last1=Inman|first1=Mason|title=World's Longest Migration Found--2X Longer Than Thought|url=http://news.nationalgeographic.com/news/2010/01/100111-worlds-longest-migration-arctic-tern-bird/|archive-url=https://web.archive.org/web/20100116190213/http://news.nationalgeographic.com/news/2010/01/100111-worlds-longest-migration-arctic-tern-bird|url-status=dead|archive-date=16 January 2010|publisher=[[National Geographic Society]]|access-date=19 August 2016|date=12 January 2010}}</ref>

A 2013 tracking study of half a dozen Arctic terns breeding in the [[Netherlands]]<ref name="Dutch terns" /> shows average annual migrations of c. {{convert|48700|km|abbr=on}}. On their way south, these birds roughly followed the coastlines of [[Europe]] and [[Africa]].<ref name="BirdGuides"/>

Arctic terns usually migrate sufficiently far offshore that they are rarely seen from land outside the breeding season.<ref name="HBW"/>