These birds have a toughness that belies their relatively small size. Travelling from the northern hemisphere to the Antarctic and back they perform the longest known regular migration of all birds. The combined round trip can be as much as 40,000km (25,000 miles), a distance that is very close to the circumference of the globe.

Arctic terns nest in colonies on the ground, rocks or shingle beaches. This leaves them open to predation. However, any predator needs to be very wary as they are extremely aggressive in defence of their nests, and will do all that they can to drive any intruders away. When threatened birds from all over the colony will rise and make repeated attacks - swooping aggressively at the head and often striking with their dagger-like bill. There is a real possibility that these attacks will draw blood from any unprotected predator.