All species › Waders, gulls and terns › Skimmers, noddies, terns and gulls › Large-billed Tern
Large-billed Tern | Phaetusa simplex
Grootsnavelstern | Charrán picudo | Trinta-réis-grande
The Large-billed Tern is a big, boldly patterned tern of the lowland rivers of South America, with a heavy yellow bill and a striking three-coloured wing pattern. It is the only species in its genus. It breeds on the sandbars that emerge in the rivers at low water.
Voice
Loud, harsh, somewhat goose-like calls such as kirrak and keh-keh, mainly when disturbed on the sandbars.
Recording: Fabrício Grigolin — CC BY-NC-SA 4.0 · xeno-canto
Identification
37–42 cm, a large tern with a very heavy, long yellow bill, a short, slightly forked tail and olive-yellow legs. In breeding plumage a black cap. The back, tail and inner wing coverts are dark grey, the outer primaries black, and between them lies a broad white triangle across the secondaries and greater coverts. The underparts are white. Outside the breeding season the cap is mottled with white on the forehead and crown. The sexes are alike. Juveniles are browner above, with a mottled head.
Confusion species
Black Skimmer Rynchops niger, often on the same sandbars, is black above with a red and black bill whose lower mandible is longer, and lacks the white wing panel. Yellow-billed Tern Sternula superciliaris also has a yellow bill, but is much smaller and pale grey above. Gull-billed Tern Gelochelidon nilotica is pale grey, with a short black bill. In flight the white panel between dark back and black primaries is shown by no other tern in the guide area.
Habitat
Large lowland rivers with sandbars, oxbow lakes, flooded plains and marshes, locally also estuaries and coastal lagoons. Mostly below 500 m. It fishes by diving into the water from flight and eats mainly fish. It breeds in small colonies or single pairs on bare sandbars, often together with Yellow-billed Terns and skimmers; the nest is a scrape in the sand.
Where the bird is most at home, classified by the vegetation units of the Andes and the west coast.
Range and movements
In Colombia in the Orinoco and Amazon basins and in the Magdalena and Cauca valleys, locally to the Caribbean coast. In Ecuador along the large rivers of the Amazonian lowlands, such as the Napo and Aguarico. In Peru along the rivers of the entire Amazonian lowlands. In Bolivia in the lowlands of the north and east, such as the Beni. Absent from the Galápagos and the Pacific coast. Outside the guide area east of the Andes to northern Argentina and Uruguay.
- Resident
- dark = core range, pale = thinly spread
How and when to look
Travel by boat or walk along large Amazonian rivers at low water, for example near Iquitos, Leticia or along the Madre de Dios, and watch for terns patrolling over the sandbars. The white wing panel stands out in flight from far away.
Conservation status
Least Concern. Locally eggs are collected and colonies are disturbed by river traffic, tourism and gold mining; dams can cause sandbars to disappear.
Scientific name
Phaetusa simplex | (Gmelin, 1789)
Gmelin described the species in 1789 as Sterna simplex; because it was later moved to another genus, the author and year stand in brackets. The genus Phaetusa was introduced in 1832 by Wagler. The genus name comes from Greek mythology: Phaethusa was one of the Heliades, daughters of Helios and Clymene and sisters of Phaethon. The species name is Latin simplex, 'simple' or 'plain'. The specimen the first description was based on came from Cayenne, French Guiana.