Of the nearly 10,000 species of birds, about 19% (1,850 species) are considered to be migratory. While there are a few species that traverse long distances, the 13-15 inch, 3.5 ounce Arctic Tern takes the prize for the longest migration. Just how far do they fly? Try an astounding 44,000 miles (71,000 km) annually on average.
Thanks to recent technological advancements, specifically tiny 1.4 gram geolocators, scientists are now better able to determine exactly where these birds migrate and how long they travel for. Before these devices, it was estimated that the Arctic Tern only traveled roughly half of the distance they really do, but now we know that of the tagged birds, the shortest migration was an astounding 36,900 miles (60,000 km) while the longest was 50,700 miles (81,000 km). For perspective, the circumference of the Earth is 24,901 miles (40,075 km).
This migration is completed annually at every life stage. Given that the Arctic Tern can live as many as 35 years, a single Arctic tern can potentially travel about 1.5 million miles (2.4 million km) in their lifetime. That is equal to 3 trips to the Moon and back!
During its migration, the Arctic Tern completes a roundtrip from Greenland, traversing the Weddell Sea and even flying along the shores of Antarctica. The birds take a break at sea over the North Atlantic Ocean while they fuel up on food (being a seabird, they eat mainly fish and marine invertebrates).
Once this break is completed, the birds head down the coast of northwest Africa, around the Cape Verde Islands, then off the west coast of Africa towards Senegal.
At this point in their travels, something very odd occurs. Rather than following the same path, only around half of the migrating birds will continue the path along the coast of Africa. The remaining birds actually cross the Atlantic Ocean and go down the coast of South America. The reason behind this isn’t fully understood; but whatever the case, both sets of birds complete their trips successfully.
The return trip also has an interesting twist. Rather than traveling straight back along the path they came, the Terns instead travel in a twisted ‘S’ shaped pattern through the Atlantic Ocean. Though this route adds many miles to their trip, it has a purpose. The birds are taking advantage of the global wind system. So although they’re taking a meandering path, they actually use less energy thanks to the wind currents.
Bonus Facts:
- Before researchers realized how far the Arctic Tern actually travels, the Sooty Shearwater was the record-holder. The longest distance traveled by this seabird was roughly 40,000 miles, covering nearly 300 miles per day. These birds travel in a circular route from the Falkland Islands to the Arctic Ocean. The Sooty Shearwater’s cousin, the Short-tailed Shearwater, is also a globetrotter. The Short-tailed Shearwater travels about 27,000 miles during its migration.
- The record-holder for migratory songbirds goes to the miniscule Northern Wheatear. Though he might be miniscule in size, weighing only 1/2 to 1.2 ounces, this bird completes a migration of epic proportions, with an annual migration of nearly 18,000 miles. Their migration goes from northern and central Asia and throughout Europe, Greenland, and sometimes even Canada. The Northern Wheatear winters over in Sub-Saharan Africa. Though many birds travel through different climates, this species travels over everything from open tundra to desert.
- You may have noticed that most migratory birds stop in various locations during their travels. There is one species that completes its entire migration in one journey! This title goes the Bar-Tailed Godwit, a wader similar to a sandpiper. The Bar-Tailed Godwit flies over 7,145 miles in only 9 days, from Alaska to New Zealand. During this entire time, these birds don’t stop for food, water, or even to rest their wings. Scientists are still baffled as to how this phenomenon is even possible.
- Though the Arctic Tern can live upwards of 35 years, they are not sexually mature until they are around 3 or 4 years old. They complete their migration to their breeding ground nonetheless.
- Scientists have discovered that nearly all Arctic Terns will return to the same area and even colony in which they themselves were hatched. The female will produce anywhere from one to three small olive or tan colored blotched eggs during the breeding season. The dark blotching on the eggs aids in camouflaging them from predators as the Tern’s nest is usually within gravel and grasses. The chicks have gray or tan down. Though their eyes are open when they hatch, they are unable to walk for a while. Chicks stay with parents for about 3 months before becoming independent. Both male and female Terns share parental responsibilities, including incubation and feeding.
