Arctic Tern: where and when to see them

The Arctic tern is a slender seabird famous for linking northern breeding grounds with the Southern Ocean through exceptionally long migrations. Its narrow wings, deeply forked tail and buoyant flight suit a life spent following marine productivity. Breeding adults have a black cap and red bill, but identification requires care where related terns occur. Despite its name, the species also breeds in temperate northern regions, including inland freshwater sites.

Size

33-39 cm body length

Weight

90-120 g

Lifespan

Not reliably established

Status

Least Concern

Arctic terns breed in colonies or scattered pairs and defend eggs and chicks with loud calls and repeated aerial attacks on intruders. Both parents incubate and deliver small prey to their young. After breeding, birds disperse along complex oceanic migration routes rather than flying directly between poles. They often hover before taking food from the surface, and communal feeding can develop where small fish or crustaceans concentrate near shore. Courtship involves aerial displays where the male presents a fish to the female, a behavior known as 'fish flights.' They are known for their aggressive defense of nests, often striking the heads of perceived threats, including humans. Post-breeding, they undergo a complete molt before embarking on their epic southward migration.

• Tracked migrations can exceed 70,000 km in a year.
• Its annual travels expose it to unusually long periods of daylight.
• Both parents incubate the eggs and provision chicks.
• Some individuals have survived for more than three decades.

June and July usually offer the strongest overlap of northern colony activity and accessible coastal travel, with May or August useful in some regions. Arrival, nesting and departure vary with latitude and weather. These northern opportunities are separate from its Southern Ocean nonbreeding period. In the Arctic, early summer offers the best chance to observe courtship rituals and early nesting activity. Observing them from ship decks during June and July provides excellent opportunities to witness their aerial foraging and colony life. The timing of their arrival and departure is highly synchronized with the peak availability of their marine prey.

Breeding habitat includes gravel beaches, low islands, rocky shorelines and sparsely vegetated tundra near water. Some pairs nest beside inland lakes and rivers. Outside breeding, Arctic terns range widely over marine waters and spend much of the northern winter in the Southern Ocean. Arctic terns undertake the longest migratory journey of any bird, traveling annually between Arctic breeding grounds and Antarctic nonbreeding areas. They prefer low-lying, often remote islands or coastal areas, making them less frequently seen on mainland shores during breeding. During their nonbreeding season, they are pelagic, spending most of their time far out at sea.

Small fish and marine crustaceans are principal foods, supplemented by insects and other invertebrates, particularly around freshwater breeding sites. Birds capture prey near the water surface. Food delivered to chicks varies locally, and shortages of suitable fish can sharply reduce breeding success. They employ a 'dip-feeding' technique, snatching prey from the water's surface while in flight or hovering. Their diet also includes small invertebrates, especially insects, which are crucial for adults and chicks in freshwater-influenced breeding areas. Local food availability and quality directly impact their reproductive success and chick survival.

Common name

Arctic Tern

Scientific name

Sterna paradisaea

Animal group

Birds

Size

33-39 cm body length

Weight

90-120 g

Lifespan

Not reliably established

Status

Least Concern

Identification

Breeding adults usually have a short all-red bill, very short red legs and longer tail streamers than common terns, though nonbreeding birds are harder to separate. Their translucent primary flight feathers, visible when backlit, are a key identification feature distinguishing them from other terns. In flight, their graceful, buoyant wingbeats and slender profile are characteristic. The long, deeply forked tail streamers extend well beyond the wingtips, especially prominent in breeding adults.