Sterna Paradisaea (Arctic Tern)

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 roundtrip lengths of about 70,900 km (44,100 mi) for birds nesting in Iceland and Greenland and c. 90,000 km (56,000 mi) for birds nesting in the Netherlands. These are by far the longest migrations known in the animal kingdom. The Arctic tern flies as well as glides through the air. It nests once every one to three years (depending on its mating cycle); once it has finished nesting it takes to the sky for another long southern migration.

Geographic Range

Circumpolar; nests on Northern European islands and peninsulas from Iceland to Northern Russia/Siberia, British Isles, Netherlands, Denmark, Sweden, the Baltic Nations, Northern Alaska, extreme of Northern Canada, Greenland, Newfoundland, and south along Atlantic Coast to Massachussetts; winters in S. Hemisphere in subantarctic and Antarctic waters of Atlantic, Pacific, and Indian Oceans.

Habitat

All terns live along seacoasts and around interior lakes and marshes.

Physical Description

Arctic terns are 14-17''(36-43 cm) long with a wingspread of 29-33''(74-84 cm). They are white with black caps and gray mantles, and a deeply-forked tail. In spring and summer, the entire bill is blood-red. Their legs are so short that the birds appear to be crouched when standing.

Other Physical Features (endothermic, bilateral symmetry)

Justification: (IUCN Red List)

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

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Arctic tern (Sterna paradisaea) feeding its young

Photo location: Jökulsárlón, Iceland

Photo info - 09.08.2008: NIKON D3, 500 mm, ISO 640, f 4, 1/5000 sec, Flash: not used

Tags: arctic tern, Erlend Haarberg, feeding, Iceland, Jökulsárlón, sterna paradisaea, tern