The Arctic Tern breeds - like the Common Tern (Sterna hirundo) – on most of the islets and islands in the fjord. It often builds its primitive nest so close to the edge of the beach that it is flooded when there is a strong on-shore wind. It frequently breeds in mixed colonies with Common Tern. The Arctic Tern can live even longer than the Common Tern. On the other hand it usually lays only two eggs, while the Common Tern lays three, which keeps the populations in balance.

The oldest specimen on the fjord, and for many years also the oldest in Denmark, was recorded at the age of 26 on Ægholm. It had also been recorded here 10 years earlier, both times breeding. It was ringed as a young bird in 1965 on the southern tip of Amager. They do not usually live so long. The average age of the Arctic Tern breeding in the fjord is a good 8 years, while that of the Common Tern is 7.



The Arctic Tern feeds primarily on small fish like, for example, stickleback, which it dives to catch. The population of breeding Arctic Tern has, unlike the Common Tern’s, increased fairly steadily over the last 25 years. This is probably mainly due to good luck. For one thing the Arctic Tern has not suffered from rat attacks to the same extent as the Common Tern, and for another they start laying eggs about a week earlier, which has saved them several times from destruction by strong winds.

The Arctic Tern does not come to the fjord until May, and they migrate again in August. Their migration (like that of the Common Tern) follows the Atlantic coast of Europe, but they go further south and some of them reach Antarctica. Their migratory flight is exceptionally long (their northernmost breeding grounds are up in the Arctic circle), and in the course of their long lives they cover huge distances – and experience very few hours of darkness!

It can be very difficult to distinguish between The Arctic Tern and the Common Tern in the wild.