Most of us get one summer a year and have to wait out the cold months in between. One small seabird skips that wait entirely. Every year, the Arctic tern trades the Arctic summer for the Antarctic summer and then flies right back.
Here's how it works. Arctic terns breed in the far north during the northern summer, in places like Greenland, Iceland, northern Europe, and North America as far south as Massachusetts. When summer ends there, they fly all the way to the coast of Antarctica, arriving for the southern summer. About six months later, they head north again. The result is two summers a year, and more daylight than any other creature on Earth.
The Longest Commute in Nature
The shortest distance between the tern's northern nesting grounds and Antarctica is about 12,000 miles. But the birds rarely take the shortest route. They follow a winding course that lets them ride the prevailing winds.
That's why scientists were surprised when they first strapped tiny tracking devices to the birds. A 2010 study of eleven terns that bred in Greenland or Iceland found they covered about 44,000 miles on average in a single year. Earlier research had seriously underestimated how far the birds really go, because it assumed they flew in straight lines.
These are by far the longest migrations known in the animal kingdom. And the record keeps growing.
One Bird Named G82
In a study that ran from 2015 to 2017, researchers tagged Arctic terns on the Farne Islands off the coast of northern England. One bird, known by its tag name G82, set a new global migration record. In just 10 months, from the end of one breeding season to the start of the next, it flew about 60,000 miles.
G82 didn't just go down the Atlantic and back. It crossed the Indian Ocean, traveled about halfway across the South Pacific, and then returned west along the Antarctic coast before heading north through the Atlantic. That's more than twice the distance around the Earth.
Even young birds get going fast. A chick ringed on the Farne Islands in the summer of 1982 turned up in Melbourne, Australia, that October, just three months after it learned to fly. That trip was more than 14,000 miles.
A Lifetime of Miles
Arctic terns are long-lived for their size. Many reach 15 to 30 years of age. Based on the tracking studies, researchers estimate that a tern living about 30 years could travel some 1.5 million miles in its lifetime. That's like flying from Earth to the Moon and back more than three times.
What makes it even more remarkable is the bird's size. An Arctic tern weighs only about 3 to 4.5 ounces and measures 13 to 14 inches from beak to tail. It has long, narrow wings, a deeply forked tail, and a blood-red beak and feet during breeding season.
Small, but Fearless
Don't let the delicate look fool you. The Arctic tern is one of the most aggressive terns, fiercely defending its nest and chicks. It will dive at people and large predators, usually striking the top or back of the head. It's too small to cause serious injury to a person, but it can draw blood.
That boldness pays off. Arctic terns can drive away many birds of prey, foxes, cats, and even polar bears that wander too close to their colonies.
So the next time winter rolls around and you're scraping ice off the windshield, spare a thought for the Arctic tern. Somewhere far to the south, a small bird is enjoying its second summer of the year, and it flew a very long way to get there.
