Arctic tern

Latin Sterna paradisaea Pont.
Estonian Randtiir

Also knows as: sea swallow, pictarnie, tarrock, tern
Status in Estonia
Breeding and migratory bird.

Description
The Arctic tern is similar to the common tern but with a smaller body, a shorter beak, head and neck, a longer tail, shorter legs and narrower wings. In the summer, an adult bird’s beak is dark red, the throat, breast and belly are a pale grey and long tail feathers hang over the tips of the rectrices when the bird is standing. The top half of the wings is uniformly light grey, and all flight feathers are whitish.

Size
Body length 33–39 cm (incl. tail feathers 7–11.5 cm), wingspan 66–77 cm, body mass 95–125 g.

Similar species
Common tern.

Distribution
It is common on Arctic Ocean beaches and bays, on smaller and bigger islands, in polar zones and on inland lake and river banks. In certain locations, the breeding habitat extends into the temperate zone along the coastline. In Europe, the Arctic tern is common in Northern and Northwestern Europe. The Arctic tern holds the record for the longest absolute migration route; its migration route runs along the coastlines of Europe and Africa and its wintering grounds are located between Africa and Antarctica, reaching south all the way to the drift ice, which is more than 17 thousand kilometres away from their breeding grounds. Estonia is almost at the southern end of its distribution range and in Latvia the species breeds in only a few dozen pairs. In Estonia, the bird mainly inhabits islands.

Population
Estonia has 9000–11,000 breeding pairs.

Occurrence in Estonia
It arrives here in mid-April. It leaves early; autumn flight and migration begins as early as the end of July and lasts through August, with the last individuals spotted in the middle of September.

Diet
The main diet is fish, which it catches by plunge-diving into the water, but it also eats marine invertebrates and flying insects.

Habitat
It primarily breeds in colonies on small islands, although it also inhabits the beach banks of bigger islands and the mainland as well as suitable shingly regions of beach meadows and borders of low-grass meadows with waterholes along the coast.

Nesting
It nests in colonies; nests are built 1–2 metres apart. The nest is usually built in a gravel hollow on the ground and thinly lined. From the end of May to the beginning of June, the female lays 2–3 eggs, which she incubates for 18–23 days. The chicks hatch within 1–4 days; the younger ones are weaker and frequently die from hunger. Both adult birds feed the chicks until they reach around a month old. The chicks can fly at the beginning of July, when they are 21–24 days old.

Conservation status and protection
It belongs to the protected bird species of category III. The same issues that threaten other ground-nesting bird species on the islands apply here: foxes lingering on the islands and other nesting birds stealing from the nest. As a breeding bird on a shingly beach influenced by the sea, their nests are frequently washed away by storms, all the more so since reeds are taking over numerous islands, resulting in fewer breeding areas. Marine pollution, especially poisons stored in fish, also has a significant impact. Arctic terns are also threatened by the increased number of people going to small islands.

Distribution and population in Lääne County
The Arctic tern is a common breeding and migratory bird in Lääne County. Birds breed in large colonies on small islands, with hundreds of nests located close together. A huge breeding colony of Arctic terns may be found in Kakrarahu, near Cape Puise, in Matsalu National Park.
However, Arctic terns can be seen in many places on the coast of Lääne County. Cape Põõsaspea is a great place to observe their migrations, especially in the spring and late summer.