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Black Tern | Chlidonias niger
Zwarte stern | Fumarel común
The Black Tern breeds in freshwater marshes in North America and Eurasia, but spends the rest of the year largely at sea. North American birds, of the subspecies surinamensis, migrate through the guide area in large numbers, both over land and along the coast. Many winter in the productive waters off the Pacific coast of Costa Rica, Panama and northwestern South America.
Voice
Rarely heard on migration; a short, sharp kik or kyek, and in flocks sometimes a nasal chatter.
Recording: Ricardo Hevia — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
22–26 cm, small, with a short, shallowly notched tail and a thin black bill. In breeding plumage the head and underparts are sooty black, with white undertail coverts, and the back, wings and tail dark slate-grey; the underwing is pale grey. In non-breeding plumage the forehead and underparts are white, with a black hindcrown and ear patch forming a cap, and a characteristic dark patch on the side of the breast. Juveniles resemble non-breeding adults, with brown-scaled upperparts. Moulting birds are blotched black and white. The legs are dark red.
Confusion species
Larger terns such as Common Tern Sterna hirundo and Forster's Tern Sterna forsteri are paler grey, have a deeper tail fork and lack the dark breast patch. Least Tern Sternula antillarum is even smaller, with a yellow bill in summer and pale grey upperparts. The Black Tern does not dive, but picks its prey from the water surface in a buoyant, swallow-like flight.
Habitat
On migration coastal waters, open sea, lagoons, lakes, reservoirs and marshes, also far inland. In winter mainly at sea off the coast, often in large flocks over shoals of fish, roosting on beaches, sandbars and floating debris. It picks insects and small fish from the surface.
Where the bird is most at home, classified by the vegetation units of Mexico and Central America.
Range and movements
On migration throughout the guide area, along both coasts and over inland waters, with the largest numbers on the Pacific side. Winters mainly off the Pacific coast of Costa Rica and Panama, with the Gulf of Panama as an important area; scarce in Mexico in winter. Outside the guide area the species breeds in Canada and the northern United States, and in Europe and Asia; American birds winter south to Peru and along the north coast of South America.
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
On migration and in winter, flocks at sea are best seen from headlands and from ferries and coastal boats in the Gulf of Panama and the Gulf of Nicoya. Over inland lakes and marshes the birds appear mainly in May and in late summer.
Conservation status
Not threatened. The North American breeding population has declined sharply since the 1960s through the loss of marshes, but the species is still numerous.
Scientific name
Chlidonias niger | (Linnaeus, 1758)
Linnaeus described the species in 1758 as Sterna nigra; because it was later moved to another genus, the author and year stand in brackets. The genus Chlidonias was introduced in 1822 by Rafinesque. Chlidonias is from Ancient Greek khelidonios 'swallow-like', from khelidon 'swallow'. niger is Latin for 'shining black'. The specimen the first description was based on came from near Uppsala, Sweden.