Animals and nature

The Arctic tern

Eleven Arctic terns carrying 1.4 g geolocators averaged 70,900 km a year between their breeding grounds and the Southern Ocean in a 2010 study.

19 facts

At a glance

70,900 km

Average yearly round trip of 11 tracked terns in a 2010 study (about 44,000 miles)

81,600 km

Longest annual journey recorded in the 2010 study (50,700 miles)

11 terns

Birds whose tracks were analysed in the 2010 study

1.4 grams

Weight of each geolocator

113 grams

Weight of an Arctic tern (4 ounces)

In a 2010 study of 11 terns tracked from Greenland and Iceland, the birds flew an average of 70,900 km (about 44,000 miles) a year, within a range of 59,500 to 81,600 km, on a round trip to the Southern Ocean and back.
The longest annual journey among the tracked terns was 81,600 km (50,700 miles).
The tracking revealed a previously unknown stopover area in the North Atlantic, used by birds from the Greenland and Iceland breeding populations.
At that stopover the terns spend almost a month at sea, probably feeding on fish and small crustaceans.

The study, led by Carsten Egevang of the Greenland Institute of Natural Resources, was published in the Proceedings of the National Academy of Sciences in 2010.
Researchers fitted geolocators weighing about 1.4 grams each to the legs of 60 terns, and the analysis tracked 11 of the birds.
Each geolocator recorded light intensity, which gave two geographical positions per day.
The tracker was light enough to be attached to a leg band.

Lifespan figures differ: National Geographic's news article says Arctic terns can live 30 years or more, while its species profile gives about 20 years in the wild.
Researchers estimate that a tern living 30 years covers about 2.4 million km (1.5 million miles), the equivalent of three trips to the moon and back.
The Royal Society for the Protection of Birds calls Arctic terns the ultimate distance migrants, flying between the UK and the Antarctic every year.

Arctic terns breed on Arctic and subarctic coasts and tundra in Europe, Asia and North America.
A tern usually first breeds at age 3 or 4 and lays 1 to 3 eggs, which both parents incubate for 20 to 24 days.
Chicks leave the nest 1 to 3 days after hatching and first fly at 21 to 28 days.
After their first flight, young terns stay with their parents for another 1 to 2 months.

An Arctic tern weighs about 113 grams (4 ounces), and Audubon gives a range of 85 to 125 grams.
It measures 35 to 42 cm long, with a wingspan of 76 to 85 cm.
Terns catch fish by hovering and plunging into the water, and they also eat crustaceans and, in summer, many insects.
Audubon lists mollusks, marine worms and earthworms among the foods terns take, and rarely berries.