Arctic Tern

## Description

The Arctic tern (Sterna paradisaea ) is a tern in the family Laridae. This bird has a circumpolar breeding distribution covering the Arctic and sub-Arctic regions of Europe, Asia, and North America (as far south as Brittany and Massachusetts). The species is strongly migratory, seeing two summers each year as it migrates along a convoluted route from its northern breeding grounds to the Antarctic coast for the southern summer and back again about six months later. Recent studies have shown average annual round-trip lengths of about 70,900 km (44,100 mi) for birds nesting in Iceland and Greenland and about 48,700 km (30,300 mi) for birds nesting in the Netherlands. These are by far the longest migrations known in the animal kingdom. The Arctic tern nests once every one to three years (depending on its mating cycle).

Arctic terns are medium-sized birds. They have a length of 28–39 cm (11–15 in) and a wingspan of 65–75 cm (26–30 in). They are mainly grey and white plumaged, with a red/orange beak and feet, white forehead, a black nape and crown (streaked white), and white cheeks. The grey mantle is 305 mm (12.0 in), and the scapulae are fringed brown, some tipped white. The upper wing is grey with a white leading edge, and the collar is completely white, as is the rump. The deeply forked tail is whitish, with grey outer webs.

Arctic terns are long-lived birds, with many reaching fifteen to thirty years of age. They eat mainly fish and small marine invertebrates. The species is abundant, with an estimated two million individuals. While the trend in the number of individuals in the species as a whole is not known, exploitation in the past has reduced this bird's numbers in the southern reaches of its ranges.

## Appearance

The Arctic tern is a species of small seabird with short legs and comparably narrow wings. Terns of different ages may have different colors at different seasons. Thus, young terns are mainly brown and gray. The color of adult terns during the breeding season varies from white to gray. The tern has red-colored legs and beak, and a black spot on its forehead and head. Meanwhile, in regular (non-breeding) season, their legs and beak become black and the black spot on its forehead decreases in size.

## Distribution

Habitat of the Arctic tern covers the huge territory, extending from arctic and sub-arctic regions of North America, Europe, and Asia to coastal regions with mild temperatures in summers, reaching as south as Brittany and Massachusetts. Within regions of their habitat, Arctic terns are met anywhere from seacoasts to lakes and swamps. As summer approaches in the Southern Hemisphere, terns migrate right up to the Antarctic Ice.

## Behavior

Terns are very communicative and sociable animals: every year they congregate for nesting in the same place, making up large groups. They fiercely defend the nesting area, building the nests close to each other. These birds see the most sun due to the fact that they migrate from the Arctic summer to Antarctica, thus living in constant summer. Arctic terns are diurnal, meaning that they are active during the day. When they search for food, they fly upward for a while and then hover in the air, looking carefully for prey on the water’s surface. During their long-distance migrations, Arctic terns stop to rest right of the water or on floating logs.

## Diet

Arctic terns are carnivores (piscivores).These birds feed upon small species of fish (sand launaes, sand eels, and capelins) as well as crayfish.

## Reproduction

Arctic terns are monogamous, meaning that they mate once in a lifetime. Migrating there and back, they usually camp in the same places every year. Mating ritual looks as follows: a male performs so-called “fish flight”, carrying caught fish through the air, accompanying the process with screaming sounds (they are able to shout with prey in their mouths), after which it lands and offers the prey to the female. Their nesting areas are rocky or sandy beaches of the far north, where the birds congregate in colonies. Before incubation, Arctic terns excavate hollows in grit or sand. Incubation takes place in summer, from June to July, lasting about 21-22 days. Female typically lays 2-3 eggs. When hatched, the chicks are downy. Neither altricial nor precocial, they begin to move around and explore their surroundings within one to three days after hatching. Usually, they do not stray far from the nest. The chicks are protected and cared by both parents during the first 10 days of their lives. After another 10-15 days they are able to fly. Both males and females of arctic terns start breeding at the age of 3-4 years.

## Population

### Population threats

Threats to Arctic terns’ population are many: rats and hedgehogs, attacking their nests; enlargement of human habitat; disturbance of terns in their home range by entertainment purposes; excessive fishing by humans, led to lack of sand eels, the major source of food for Arctic terns. In addition, changes, now taking place in Arctic and Antarctic ecosystems, will definitely affect Arctic terns.

### Population number

The total population of Arctic tern is officially estimated by IUCN, counting up to 2 million individuals. Thus, in Russia only, 10.000-100.000 breeding pairs and 1.000-10 migrating individuals have been estimated. The population as a whole isn’t endangered, being listed in the IUCN Red List as of Least Concern (LC) with a decreasing population trend.

### Ecological niche

Being sea predators, these birds noticeably control the marine ecosystem in their habitat. They influence the population number of species they feed on. Sometimes they catch and leave the prey, giving opportunity local scavengers to take advantage of it. And finally, Arctic terns serve as the major source of food for many animal species of the area.

## Fun Facts for Kids

Hatching out, chicks of terns usually have 2 colors - brown and gray - while they occasionally have different colors, even coming from one family.

To the date, the oldest Arctic tern ever recorded was found in Maine (USA) and was 34 years old. After being studied, it was released back into the wild.

Due to migratory lifestyle, these birds see two summers a year thus seeing more sunlight than any other animal on the planet.

In addition, the longest migration route on the earth belongs to Arctic terns. For example, those nesting in the Netherlands, pass a huge distance of as long as 90.000 km per year: this is longer than the migration route of any other animal.

An average Arctic tern travels about 2,400,000 km distance during its life. To compare: the distance between the earth and the moon is less than 400.000 km.

There’s a phenomenon, called “dread moment”. It’s when a group of Arctic terns, just before taking flight, grows totally silent for a short time.

In order to save energy during long flights, terns, instead of flapping their wings, use the hang-gliding technique. In fact, they are exceptional gliders, managing even to take a rest or sleep while gliding.

Arctic terns, along with Hummingbirds, are the only species of birds that exercise “free flight” or hover.