Common Tern vs Arctic Tern: How to Tell Them Apart

The Common Tern resembles the Arctic Tern, but some differences include the reddish-orange bill with a black tip, the paler underparts and the proportionally longer red legs. In summer the upperparts are silver-grey, it has a dark cap, and when flying the tips of the underwing feathers are dark and there's a section on the wings that can appear almost transparent. The longest flight feathers grow darker as summer progresses, appearing as a dark wedge shape. Winter plumage is similar, but the forehead whitens leaving a black bar and the bill and legs darken. Juvenile birds are white underneath, they have a partially formed dark cap, the upperparts are scaly-looking and grey, and the back is ginger. The bill is fleshy in colour or yellowish and it has a dark tip which becomes more prominent over the summer.

Breeding grounds are beaches of sand or shingle, or on craggy seashores. Feeding is usually done on inshore waters like lakes and rivers. Prefers warmer sea waters when not breeding.

Has a variety of coarse calls, the most common being 'kreee-yaah'.

A slighter bird than the Common Tern, the Arctic Tern is only seen in summer plumage in the region. The sexes are similar. Underparts are pale, smoky grey, and are lightest on the throat and cheeks, darkening on the belly. The upperparts are grey, the rump white, it has a black cap, long tail streamers, short red legs, and a red bill. When flying, flight feathers can appear opaque, and there's a dark trailing edge; wings look grey from above. Juvenile birds are white underneath, upperparts are scaly and grey, there's a partial black cap, white forehead, and a red base on the black bill. Wings have a dark leading edge and a white trailing one when flying.

Breeding grounds are predominately on the coast or on offshore islands; may also go to rivers where there are rocky islands and stone beaches. When not breeding, lives almost exclusively at sea.

Has a grating 'kee-arr', or a shrill 'krt-krt-krt' that's usually uttered in close proximity to the nest.