Arctic Tern

Arctic Tern engage in elegant aerial displays and are adept at hovering and diving to capture their prey, which they consume adeptly. They are social creatures, forming large, noisy colonies where they exhibit remarkable ritualized courtship, including aerial displays and food sharing, which strengthens monogamous pair bonds. Vigilant in defending their territories, they adopt postures ranging from submissive to aggressive to deter intruders, and are known for their aggressive defense tactics against humans and other threats.

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 Eurasia during the northern summer. During the southern summer, it can be found at sea, reaching the northern edge of the Antarctic ice. 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 being 19,000 km (12,000 mi). The long journey ensures that this bird sees two summers per year and more daylight than any other creature on the planet. One example of this bird's remarkable long-distance flying abilities involves an Arctic tern ringed as an unfledged chick on the Farne Islands, Northumberland, UK, in the northern summer of 1982, which reached Melbourne, Australia in October 1982, just three months from fledging – a journey of over 22,000 km (14,000 mi). Another example is that of a chick ringed in Labrador, Canada, on 23 July 1928. It was found in South Africa four months later. A 2010 study using tracking devices attached to the birds showed that the above examples are not unusual for the species. In fact, it turned out, previous research had seriously underestimated the annual distances travelled by the Arctic tern. Eleven birds that bred in Greenland or Iceland covered 70,900 km (44,100 mi) on average in a year, with a maximum of 81,600 km (50,700 mi). 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. The average Arctic tern lives about thirty years, and will, based on the above research, travel some 2.4 million km (1.5 million mi) during its lifetime, the equivalent of a roundtrip from Earth to the Moon over 3 times. A 2013 tracking study of half a dozen Arctic terns breeding in the Netherlands shows average annual migrations of c. 48,700 km (30,300 mi). On their way south, these birds roughly followed the coastlines of Europe and Africa. Having rounded the southern tip of Africa, they then turned east, some flying approximately halfway to Australia before again turning south to eventually reach Wilkes Land in the north-eastern Antarctic. One bird flew several hundred kilometres along the south coast of Australia before turning south for the Antarctic, while one flew along the entire south coast of Australia, passing between Australia and Tasmania. Having reached the Melbourne area, it turned south and flew in an arc to Wilkes Land in the north-east Antarctic, passing the south-western tip of New Zealand's South Island en route. Once back in the Netherlands, this bird had flown c. 91,000 km (57,000 mi) in the course of migrating to and foraging in Antarctica. Arctic terns usually migrate sufficiently far offshore that they are rarely seen from land outside the breeding season.

Arctic terns are considered threatened or a species of concern in certain states. They are also among the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds applies. The species reduced population in New England in the late nineteenth-century because of hunting for the millinery trade. Exploitation continues in western Greenland, where the population of the species has been reduced greatly since 1950. In Iceland, the Arctic tern has been regionally uplisted to Vulnerable as of 2018, due to the crash of sandeel (Ammodytes spp.) stocks. At the southern part of their range, the Arctic tern has been reducing in numbers. Much of this is due to lack of food. However, most of these birds' range is extremely remote, with no apparent trend in the species as a whole. BirdLife International has considered the species to be at lower risk since 1988, believing that there are approximately one million individuals around the world.