The Arctic tern sees two summers a year and more daylight than any animal.
Each year the Arctic tern flies from its northern breeding grounds to the edge of Antarctica and back, chasing summer at both ends of the planet. Tracking shows its winding route can exceed 70,000 kilometres a year. One bird from England logged 96,000 kilometres in ten months, the longest migration known.
The Arctic tern is a slender grey-and-white seabird weighing only about 100 grams, with a blood-red bill and a black cap. It breeds around the Arctic and subarctic coasts of Europe, Asia and North America. When the northern summer ends, it heads south to spend the southern summer at sea near the Antarctic ice. The shortest distance between the two is about 19,000 kilometres, and by making the trip it enjoys two summers a year and more daylight than any other creature.
For a long time the true distance was underestimated, because researchers assumed the birds flew fairly direct routes. A 2010 study fitted tiny tracking devices to terns breeding in Greenland and Iceland and found they averaged 70,900 kilometres a year, one reaching 81,600. Rather than flying straight, the birds take meandering courses that make use of prevailing winds. Birds from the Netherlands, tracked in 2013, averaged about 48,700 kilometres, following the coasts of Europe and Africa on the way south.
Then, in a 2015–2017 study on the Farne Islands off Northumberland, a tern tagged 'G82' covered 96,000 kilometres in the ten months between breeding seasons. It flew the length of the Atlantic, across the Indian Ocean and halfway across the South Pacific before returning along the Antarctic coast, more than twice the Earth's circumference. Terns can live around 30 years, so one bird might fly some 2.4 million kilometres in a lifetime, the equivalent of more than three return trips to the Moon.
At the nest they are anything but delicate. Pairs mate for life and usually return to the same colony each year, and parents dive at intruders, people included, striking the head hard enough to draw blood. The global population is estimated at over two million and the species is listed as of least concern, although numbers have fallen in parts of its range. In Iceland it was regionally uplisted to vulnerable in 2018 after a crash in the sand eels it feeds on.
Source: Wikipedia — Arctic tern · Text summarised from Wikipedia (CC BY-SA 4.0)
