| Arctic Tern | |
|---|---|
 | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Laridae |
| Genus: | Sterna |
| Species: | Sterna paradisaea |
The Arctic Tern (Sterna paradisaea) is a seabird in the family Laridae. It is known for having the longest migration of any bird.
Description[]
The Arctic tern is a species of small seabird with short legs and comparably narrow wings. A slender, dainty bird with long, pointed wings and a forked tail, the Arctic Tern measures 66-79 cm (26-31 in) in wingspan and 33-39 cm (13-15½ in) in length including the tail streamers, which are 7-11½ cm (2,3-4,5 in) long. Compared to the Common Tern, the Arctic Tern is slightly smaller, with a rounder head, a shorter neck, shorter legs, a shorter bill, and longer tail streamers which extend past the wingtips when perched. The adult in breeding plumage is medium grey above and paler below, with a black cap and nape and uniformly grey wings with a very narrow black line on the trailing edge of the primaries, lacking the dark wedge of the Common Tern. The grey plumage creates a contrast with the white throat and upper cheeks. All flight feathers appear white and translucent from below. The legs are red in colour and very short, and the bill, fine and pointed, is solid blood-red with no black tip. Meanwhile, in regular (non-breeding) season, their legs and beak become black and the black spot on its forehead decreases in size. The juvenile usually lacks the brownish wash of the juvenile Common Tern and has a fainter carpal bar. It has a white forehead, grey primaries and white secondaries, and an initially red-based bill which quickly turns black.
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[]
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.
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[]
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.
Gallery[]
