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Common Tern | Sterna hirundo
Visdief | Charrán común | Trinta-réis-boreal
The Common Tern is a medium-sized tern with a very large range: it breeds in North America, Europe and Asia and winters as far as southern South America, Africa and Australia. The birds in the guide area come from North America. Along the Pacific coast it is one of the most numerous terns outside the breeding season, often in flocks of tens to hundreds of birds.
Voice
A shrill, descending kreee-ah and a short kik; flocks keep up a constant screeching.
Recording: Lionel FREDERIC — CC BY-NC-SA 4.0 · xeno-canto
Identification
31–37 cm including the tail streamers. In non-breeding plumage, the plumage in which most birds in the guide area are seen, the forehead is white, with a black hindcrown extending onto the nape, a dark bar along the leading edge of the inner wing, a black bill and dark red legs. The upperparts are pale grey, the underparts white. In flight the outer primaries form a dark wedge on the upperwing; from below only the inner primaries are translucent, with a broad, diffuse dark trailing edge. In breeding plumage, sometimes from March, the cap is black, the bill red with a black tip and the underparts tinged pale grey. Juveniles have a brownish-tinged mantle with dark scaling and a dark bar on the forewing. The sexes are alike.
Confusion species
Arctic Tern Sterna paradisaea has shorter legs, a shorter bill, a rounder head and from below translucent primaries with a narrow, sharp black trailing edge. Forster's Tern Sterna forsteri has a well-defined black eye mask and silvery white primaries in non-breeding plumage. South American Tern Sterna hirundinacea is larger, with a heavier red bill. Black Tern Chlidonias niger is smaller and dark grey above, with a short, barely forked tail.
Habitat
Beaches, river mouths, lagoons, salt pans and harbours; it forages over shallow water and at sea close inshore, also in the wake of fishing boats. It plunge-dives from a few metres for small fish. It roosts in groups on beaches and sandbars, often with other terns. Rarely inland, on large rivers and lakes. It does not breed in the guide area.
Where the bird is most at home, classified by the vegetation units of the Andes and the west coast.
Range and movements
In Colombia along the Caribbean and Pacific coasts. In Ecuador and Peru along the whole coast, locally common, especially in northern Peru. A rare visitor to the Galápagos. Inland, including Bolivia and the Amazonian lowlands, only a few records of migrants. Breeds in temperate and northern regions of North America, Europe and Asia; American birds winter from Central America and the Caribbean to Argentina and Chile.
- Resident
- Summer visitor (c. Apr–Sep)
- Winter visitor (c. Oct–Mar)
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
On beaches and at river mouths along the coast of Ecuador and northern Peru, mainly from October to April; check flocks for odd birds, such as Arctic Terns with shorter legs. Immature birds also stay through the northern summer.
Conservation status
Least Concern. Locally declined through the loss and disturbance of breeding sites; in the wintering range birds are sometimes caught in fishing nets.
Scientific name
Sterna hirundo | Linnaeus, 1758
Linnaeus described the species in 1758 and placed it straight away in the genus where it still stands. He introduced the genus Sterna in that same work. The genus name comes from Old English stearn, a word for a tern; the Frisians had a similar word. The species name is Latin hirundo, 'swallow', for the forked tail. The specimen the first description was based on came from Sweden.