Arctic Tern Fun Facts: Their Lifetime Journey Equals 3 Round-Trips to the Moon

The Arctic tern is one of the most magnificent birds in the world. It holds the record for the longest migration of any known animal. So, how can they do that? Let’s uncover interesting facts about these birds and their incredible abilities.

1. They’re the smallest terns

The Arctic tern, one of the most remarkable species in the Arctic, is a slender bird. It belongs to the tern family and stands out as one of the smallest members, with a size of about 11 – 15 inches (28-39 cm) in length and weighing around 3.2-4.2 oz (90-120 g).

With their small heads, short legs, and slim bills, they possess a lightweight nature that allows them to be carried by the wind, minimizing energy expenditure during their long-distance flights. Additionally, they have webbed feet, enabling better swimming ability.

The wings of the arctic tern are their outstanding characteristic. These avian creatures possess elongated, slender wings with sharp, pointed tips. This special feature, coupled with their deeply forked tails and abundant streamer feathers, allows the terns to effortlessly glide through the air, capitalizing on updrafts and air currents, all while conserving energy during their extensive migrations. They have a lighter and smaller wingspan than those of common terns, ranging from 25 to 30 inches (64-76cm).

These terns possess unique appearances. Adult Arctic terns showcase a pale gray plumage both above and below, adorned with a distinctively full black cap that extends down the back of their necks. They also boast a vibrant red beak and legs.

On the other hand, the juveniles sport a darker grey mantle with a white forehead accompanied by a smaller black cap that is limited to the back of their heads and necks. Their tail feathers are shorter and their bill and legs are black, not red. The newborns have either gray or brown plumage.

Although the Arctic terns bear a resemblance to the common tern and roseate tern, they can be identified by their longer tails and wings.

2. Common terns vs Arctic terns

These two birds are very similar. If you don’t look at them carefully, you hardly see the differences between them.

3. They live on 2 poles of Earth

Arctic terns are migratory birds. They embark on extensive voyages between the northern and southern hemispheres, strategically avoiding severe winters and evading predators while capitalizing on diverse food sources in various regions.

Throughout the summer in the northern hemisphere, Arctic Terns establish their nesting sites in various regions spanning from Asia to Europe to North America. Alaska and Iceland serve as two prime breeding grounds that provide plentiful food resources and fewer predators. Alaska is home to the largest breeding population of these birds. Arctic terns can be found breeding in a variety of locations, ranging from treeless areas in the Arctic to open boreal forests and islands along the northeastern Atlantic Coast.

When the winter comes, they migrate to the south to enjoy the southern summer. During this time, these birds gather at the northern boundary of the Antarctic ice.

The species exhibit a preference for coastal habitats situated near bodies of water that offer an abundance of fish and minimal predation risk. This habitat preference remains consistent across all the regions they inhabit.

4. They steal food

Arctic terns have a diverse diet that changes based on their migratory phases and the availability of food resources. When migrating to the Antarctic in winter, this magnificent creature primarily eats fish, with a particular preference for small schooling species such as smelt, cod, and sand eels.

The secondary consumers get the food from the sea surface or dive into the water at a depth of 20 inches with impressive speeds, using their specialized beaks, to capture fish. They emerge and swiftly gulp down their prey, swallowing it headfirst. These terns also consume crabs, krill, and mollusks.

While nesting in the Arctic, these omnivores can also feed on insects and berries. This adaptability enables the Arctic tern to adjust to various environments and seek alternative food sources as necessary.

In times of limited resources, Arctic terns employ a form of kleptoparasitism similar to the Arctic skua. With their fast speed (about 25mph ~ 40 kph), they startle birds such as common terns or auks, following and inducing them to abandon or release their prey. Then, they swiftly seize the opportunity and steal that food.

These birds face various predators such as bigger birds (skuas, petrels, and gulls), cats, and foxes. To defend themselves and their nest, these aggressive birds employ assertive strategies like emitting loud screeches and engaging in dive-bombing maneuvers to discourage intruders.

These defensive tactics are so effective that many other bird species choose nesting locations near Arctic terns. This helps them take advantage of Arctic terns’ protective abilities. Nevertheless, in the event of excessive predation, these terns might choose to completely forsake their nests.

5. They migrate to the end of Earth

Arctic terns are renowned for their remarkable migration and claim the title “Champion of Migration” for the most extensive journey undertaken by any creature on our planet. These petite seabirds embark on an annual voyage from the Arctic Circle to the Antarctic Circle, traversing unbelievable distances of nearly 60,000 miles (~96,561 km) – the longest migration. This distance exceeds twice the Earth’s circumference. Over their lifetimes, they cover an estimated 1.491 million miles (2.4 million km), which is equivalent to undertaking three round-trip flights to the Moon.

During the breeding season from May to July, these birds establish their nests in the Arctic region. Once this period ends (from November to February), they migrate to the Antarctic Circle. There, they enjoy the summer season of the Southern Hemisphere, taking advantage of the plentiful food resources available.

Interestingly, instead of opting for a direct migration route, they embark on a meandering journey spanning across every ocean and continent. They gracefully navigate their way, guided by the sun and favorable weather patterns, occasionally taking detours to discover more abundant feeding grounds or to evade harsh weather conditions. It takes them about 3 months to finish the journey.

As a result of their migration pattern, these birds encounter year-round perpetual summer seasons and benefit from the most extensive daylight exposure of any creature on Earth.

Throughout their migration, the terns display fascinating behaviors. Before taking flight, they enter a state of silence known as the “dread.” During their journey, they engage in prolonged gliding, enabling them to rest and even sleep while in mid-flight. Their gliding skills are remarkable, comparable to the hovering ability of hummingbirds.

Thanks to some special characteristics, Arctic terns can take a long migration like that. As mentioned earlier, their lightweight bodies, short legs, and slender wings enable them to effortlessly glide through the skies. They can also use the wind system to maintain remarkable speeds and cover vast distances.

To be able to take a long flight, these terns rely on a high-fat diet and have developed techniques to feed while flying, reducing the need for frequent stops during their extensive global migration.

Like most migratory birds, Arctic terns migrate in a pattern. Big flocks journey from the northern polar areas, crossing over the Atlantic Ocean and tracing the European coastline. As they approach the equator, the congregation divides into two small groups, with one group flying along the South American coastline (known as western terns) while the other half navigates Africa’s coast (referred as the eastern terns). Both groups synchronize their arrival in Antarctica, almost simultaneously.

Intriguingly, the northward migration of Arctic terns does not exhibit a clear separation at the equator, and various groups of these birds follow similar paths when returning to the northern polar region.

The yearly expedition of these terns around the world highlights their remarkable resilience, adaptability, and expertise in undertaking long-distance flights.

6. Behavior

Arctic Terns display strong social behavior, residing in extensive colonies. To communicate with other birds, they use diverse sounds. Their sharp and piercing calls can repel predators and humans who may disrupt their nesting sites.

When these terns arrive in Antarctica during the summer months of the southern hemisphere, they molt. They choose to rest on the ice and shed their old feathers, enabling new and more robust plumage to grow. At this time, their flying ability is limited. However, they are still quite safe in Antarctica, where threats from predators are minimal, food is plentiful, and the climate is mild. Consequently, this extraordinary location serves as an optimal molting site for them.

7. Life cycle

Arctic terns are monogamous birds. They mate for life and faithfully return to their designated colony year after year. To attract potential mates, they engage in a special mating ritual. The female takes the lead in pursuing the male during a captivating “high flight.” They gracefully ascend into the sky and gradually descend together toward the ground.

After that, the male partakes in the enchanting “fish flight,” skillfully snatching fish from the water and soaring through the air, accompanied by resounding screeches. He then lands in front of the female and gives her the captured fish. If the female is satisfied, the two birds will form a breeding pair, showcasing their wings in a display of strutting and posturing.

Both the male and female make nests together in shallow indentations on the ground, often close to water or in rocky and sandy environments. The male keeps feeding his partner and the female lays a clutch of 1 – 3 eggs, with two being the most common.

The pair vigorously protects their nest from intruders. They exhibit different aggressive postures and directly attack their enemies, such as wrestling and fencing with their bills. When humans intrude, they can peck on their heads, dive bombs, and even defecate.

The female will incubate her eggs for about 3 – 4 weeks. These chicks will be fed by both parents, who take turns in this task. In the beginning, the amount of food provided gradually escalates. Around one month later, the young start to learn how to dive to get fish independently.

The birds reach sexual maturity at approximately 3 years old. However, they usually breed 1 time per 3 years. They prioritize their migratory journeys more than reproduction. Arctic terns live quite long, about 20 to 30 years, with the longest recorded lifespan being 34 years. This extended lifespan is similar to that of other tern species like the white and sooty terns.

8. They are endangered

Arctic terns are listed as Least Concerned on the Red List of Threatened Species by the IUCN with about 2 million population. However, they are facing a significant reduction of 20 – 50% in their habitat due to the effects of climate change and associated temperature changes.

With potential habitat loss and disruptions in food availability due to climate change, the terns face challenges in finding prey and maintaining breeding success. The increasing of sea temperatures is leading to the emergence of storms, which in turn disrupt the breeding patterns of Arctic terns.

The detrimental effects on these birds are further exacerbated by various human activities and exploitations taking place along the Alaskan coastline. These activities include hunting, trade, and oil drilling. Additionally, the presence of invasive species, such as the American mink, adds to the negative impacts on the bird populations.

References:

• Nationalgeographic.com
• Polarguidebook.com