Annual Migration
~70,000 km
The longest migration of any known animal on Earth
Arctic Tern in Iceland: World's Longest Migration
The holder of the longest migration of any bird on Earth, flying from the Arctic to Antarctica and back every year, a round trip of up to 70,000 km.
Location
Nationwide
Coastal meadows, lake shores, offshore islands
Quick Answer
Arctic terns fly up to 70,000 km a year between Iceland and Antarctica. Where they nest May-August, why they dive-bomb, and how to walk near colonies safely.
The Arctic tern (Sterna paradisaea), known as "kría" in Icelandic, migrates each year from its Arctic breeding grounds to the Antarctic pack ice and back, a round trip of up to 70,000 km and the longest known migration of any animal. Iceland is one of the species' most important breeding grounds, with hundreds of thousands of pairs nesting across the country from May to August. Arctic terns are also notorious for defending their nesting territories, and they dive-bomb any intruder, humans included, who ventures too close.
Sources and page update
Updated: 2026-09-10
Arctic terns aggressively defend nests. Hold an object above your head when walking near nesting areas and stay on marked paths.
For sourcing standards and how to report an error, see the editorial policy.
Breeding Season
May–August
Nests across Iceland on flat, open ground near water
Lifespan
30+ years
Equivalent to 2.4 million km of migration in a lifetime
What to Expect
Population estimate
The old 250,000–500,000-pair estimate dates to around 1990 and was judged too high by Náttúrufræðistofnun. Its species account revises the historical estimate to 150,000–250,000 pairs; this is not a 2026 census.
Best viewing: May-August
Terns are present in Iceland from early May through late August. Peak colony activity is June-July when eggs are incubating and chicks are being fed.
Specific viewing locations
Large colonies at Jökulsárlón, Vík, Lake Mývatn, the Westman Islands, and Grímsey island. In Reykjavík, terns nest in grassy areas and on urban rooftops near Seltjarnarnes.
Dive-bombing defense
Terns attack anything near nests, striking the highest point. Hold a stick, hat, or your hand above your head for protection. Peak aggression is June through mid-July.
70,000 km annual migration
The longest migration of any animal on Earth: Arctic to Antarctic and back. Over a 30+ year lifespan, one tern may travel 2.4 million km (equivalent to three Moon round trips).
Hovering hunters
Watch them hover motionless above the water before plunge-diving to catch small fish near the surface. Forked tails and narrow wings make them agile in the air.
Where to See Them
Arctic terns nest across Iceland wherever suitable flat, open habitat exists near water. Major colonies: Jökulsárlón glacier lagoon (south coast, directly on Route 1, 330 km from Reykjavík); along the coast near Vík (Route 1, 180 km from Reykjavík); Lake Mývatn in the north (Route 1, 100 km east of Akureyri); the Westman Islands (30-minute ferry from Landeyjahöfn); and Grímsey island on the Arctic Circle (3-hour ferry from Dalvík or 25-minute flight from Akureyri). In Reykjavík, terns nest on grassy areas at Seltjarnarnes peninsula (bus route 11) and on urban rooftops. No 4WD required for any viewing location. Nesting areas are usually marked with warning signs; stay on paths.
Best Time to Visit
Arctic terns are present in Iceland from early May through late August. May: Arrival and territory establishment; birds active but not yet aggressively defensive; best month for calm observation. June: Egg incubation and early chick rearing; peak aggressive nest defense begins; colonies are at their noisiest and most active. July: Chicks growing and being fed; dive-bombing at its most intense around nests; photograph from a respectful distance. August: Chicks fledging; defensive behavior subsiding; by late August the entire population begins departing for Antarctica. September-April: No Arctic terns in Iceland; they are in the Southern Hemisphere. For observation with minimal dive-bombing, visit in early May or late August.
Large colonies do not mean a secure population
Náttúrufræðistofnun lists the Arctic tern as Vulnerable in Iceland. Its assessment describes poor breeding since the sand-eel decline that began in 2005, especially in the south and west, while individual colonies have changed differently. A busy colony is therefore a local observation, not evidence of a national recovery. Watch from the marked route and turn back if birds repeatedly dive toward you.
Planning help
Arctic Tern FAQs
Quick answers with safety notes where it matters.
How far do Arctic terns migrate?
Arctic terns complete the longest known migration of any animal, flying roughly 70,000 km per year. They breed in the Arctic (including Iceland) from May to August, then fly south to Antarctica for the southern summer, and back again. Over their 30+ year lifespan, a single tern may travel the equivalent of three round trips to the Moon.
Will Arctic terns really attack people?
Yes. Arctic terns aggressively defend their nests from any perceived threat, including humans. They dive-bomb intruders, striking with their sharp beaks at the highest point, usually the top of your head. Hold a stick, hat, or your hand above your head while walking through nesting areas. They target the highest point and will usually strike that instead of your head.
Where do Arctic terns nest in Iceland?
Arctic terns nest across Iceland in colonies ranging from a few pairs to thousands. They prefer flat, open ground near water: coastal meadows, gravel flats, offshore islands, and lake shores. Large colonies are found at Jökulsárlón, along the south coast, at Lake Mývatn, and on the Westman Islands. Nesting areas are often marked with warning signs.
What do Arctic terns eat?
Arctic terns feed primarily on small fish (sand eels, capelin, sticklebacks) and small crustaceans. They hunt by hovering above the water and plunge-diving to catch prey near the surface. During migration, they also feed on krill and small marine organisms. Their dependence on sand eels makes them sensitive to the same ocean temperature changes affecting puffins.
For more context on Iceland’s people and rural life, explore our Iceland statistics.