Common Tern bird is a slender and graceful bird, with a black-tipped orange-red bill and red legs, long wings and a deeply forked tail with extended outer tail-feathers forming long streamers. The cap and nape are black, the upperparts pearly grey.Common Tern bird is very similar to Arctic Tern, but dark-tipped bill and longer legs help distinguish it, as does the subtle wing pattern. It shows a smoky trailing edge to the outer primaries that extends inwards along the middle (fourth-sixth) primary feathers to form a dusky wedge, contrasting with translucent inner primaries. This feature is less obvious in fresher spring plumage.
When breeding, Common Tern bird uses the widest range of habitats - both coastal and inland - of all our terns. Prefers safe nesting sites out of reach of predators, such as inshore islands and islets, lagoons, quiet beaches, shingle and sand spits, dunes and saltmarshes, above the reach of the highest tides. Inland it can be found along slow-flowing rivers, gravel pits, lakes and marshes, nesting on islands and gravel banks and occasionally on manmade 'tern rafts'. Outside the breeding season, Common Tern bird can be found widely as a migrant in coastal and freshwater habitats, spending the winter off the coasts of Africa.
Common Tern bird is vocal and noisy, particularly in the breeding season, it gives a variety of harsh screeching and shrill calls that are lower in pitch than Arctic Tern, such as a short sharp "kit", often repeated in a series of quarrelling notes such as "ik'ik'ik'ik" or "kt'kt'kt'kt'kt". A downwards-inflected monosyllabic or disyllabic call is commonly given, such as "keeee-yaaa" or "eee-arrr", and this is often combined with other calls like "kit-kit-kit keee-yaaa" and "i'i'i'eeeeyah". Longer series of calls are also given, such as "kirri-kirri-kirri-kirri" or"irri'irri'irri'irri", "ea'i'ea'i'ea'i'ea'i", and a harsher, scolding "krrrr'krrr'krrrr'krrr". Juveniles following their parents call with a shrill "keee".