Arctic terns are a little smaller than common terns - another difference is that their bills are entirely red (no black tip as the common terns have) and their tails streamers are longer

The rump is white, the underparts are darker and the wing lacks the dark wedge on the outer edge

The males and the females have similar plumage and both have a black mask.

The Arctic terns feet are webbed. The legs are red and very short and the birds have a white head with a red pointed beak.

The bottom of their wings are pale grey or ivory. The young arctic terns have pale red coloured legs - they have full plumage in their third year

• Courtship starts with the female chasing the male and then descending slowly. The male then offers fish to the female and lots of strutting with tails raised and then the birds fly and circle each other
  
  The arctic terns can be really aggressive in defending the nest and their young - will even attach humans. The chicks are quite quick to be moving around the nest site within a few days - although not straying far. The adults brood the chicks for ten days after hatching.
  
  The chicks eat the prey brought by the adult terns for about a month before fledging and learning the art of plunge diving