The Arctic tern is a small seabird that breeds in the Arctic and sub-Arctic regions. Arctic terns are known for their extraordinarily long annual migrations from their Arctic breeding grounds to the Antarctic region. This round-trip journey can cover over 70,000 km each year, making the Arctic tern the bird with the longest migration in the world. Given their extreme migratory habits, Arctic terns do not hibernate. Instead, they migrate huge distances to find abundant food and suitable breeding conditions throughout the year.
Arctic Tern Breeding and Migration
Arctic terns nest in the far north, above the Arctic Circle, during the summer months of May to August. Their breeding grounds extend across northernmost North America, Greenland, northern Europe, and Siberia. On these sites, they lay 1-3 eggs and raise their chicks until they fledge at around 3-4 weeks old.
As soon as the Arctic summer ends, Arctic terns embark on their phenomenally long migration south. They fly down the coasts of North and South America, crossing the equator to reach their main wintering grounds in the Antarctic pack ice zone. Some birds may fly even further, crossing the Antarctic Circle to forage in the Weddell and Ross Seas near Antarctica.
This journey sees Arctic terns traveling along coastal, polar, and pelagic habitats. They rarely stop on land, instead resting and feeding on the wing. Their non-stop migratory flight averages around 500 km per day. By the time they reach Antarctica in November, individual birds will have flown over 20,000 km from their Arctic nest sites.
Come March, the terns begin the long flight back north to their breeding grounds. They follow a similar coastal route up South America and North America to return to the Arctic by May. In total, the round trip between Arctic and Antarctic can cover over 90,000 km!
Why Arctic Terns Migrate
The key reason Arctic terns migrate such enormous distances is to take advantage of the peak breeding and feeding conditions in the far north and far south.
In the Arctic summer, the 24 hours of daylight provide perfect nesting conditions. Arctic terns time their breeding season to coincide with the temporary abundance of fish, marine invertebrates, and aquatic insects to feed themselves and their chicks.
As winter approaches, food becomes scarce in the freezing Arctic waters. So the terns migrate south to ice-free waters in the Antarctic, where summer is just beginning. Here, they can feed on the seasonally plentiful Antarctic krill as well as fish and squid. Spending the winter in the southern polar region allows the terns to take advantage of the austral summer and build up reserves for their journey back north.
The Arctic tern’s migratory strategy enables them to experience endless summer – breeding, feeding, and raising chicks in the far north’s summer, then promptly moving south to enjoy the southern summer too!
Why Arctic Terns Don’t Hibernate
Hibernation is an adaptation used by some animals to survive cold winters with scarce food. By entering a dormant state, hibernating mammals and reptiles can conserve energy and survive on limited winter resources until spring arrives.
Arctic terns, however, are migratory birds that travel enormous distances rather than dealing with the hardships of winter. Here are some key reasons why Arctic terns migrate instead of hibernating:
– Birds cannot store enough energy: Hibernation requires animals to build up immense fat reserves to power them through the winter. Small birds like terns cannot store enough body fat to survive the Arctic winter without feeding.
– Reduced food: Hibernation only works because animals minimize energy use by staying dormant. However, Arctic terns rely on catching live prey, which becomes scarce in winter.
– Unsuitable Arctic conditions: The Arctic has 24-hour darkness in winter, along with extreme cold and frozen waters. These conditions make nesting, breeding, and fishing impossible for terns.
– Migration lets them “escape winter”: Instead of facing the inhospitable Arctic winter, migration allows terns to stay productive by moving somewhere with better conditions.
– Takes advantage of seasonal resources: Migration enables Arctic terns to breed in the northern summer, then winter in Antarctica’s summer, following peak seasonal food availability.
Overall, migration provides major advantages for Arctic terns compared to attempting to overcome the Arctic winter. Their migratory instinct ensures they can keep feeding, breeding, and raising chicks despite the extreme changes between Arctic summer and winter.
Arctic Tern Migration Facts
– Arctic terns hold the record for the longest migration of any bird, flying over 70,000 km annually between Arctic and Antarctic.
– Their pole-to-pole round trip covers up to 90,000 km per year.
– Arctic terns fly an average of 500 km per day on migration.
– Individual birds spend over 99% of their lives in flight or on the ocean.
– Their migration strategy means Arctic terns see more daylight hours than any other species, experiencing two summers per year.
– Adults make the massive Arctic-Antarctic round trip journey every year for up to 30 years.
– Young Arctic terns may take 2-3 years to complete a full migration cycle.
– Arctic terns fly along coastal routes, rarely stopping on land. They rest and feed while flying or floating on the sea surface.
– Arctic terns have the longest life expectancy (up to 34 years) of any seabird.
– Changes to Arctic climate and sea ice extent may impact terns’ breeding habitat and migration routes.
Conclusion
In summary, Arctic terns are champion marathon migrators that complete an annual pole-to-pole round trip of up to 90,000 km. Their extreme migration enables them to evade the harsh Arctic winter and exploit seasonal peaks in food availability in both polar regions. Arctic terns rely on this incredible migration strategy to breed, feed, and raise chicks for over three decades of their life cycle. Unlike some animals, terns are unable to hibernate through the challenging conditions of an Arctic winter. Instead, their amazing migratory instincts bring them ceaseless summer as they move between the northern and southern polar circles every year.