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Large-billed Tern | Phaetusa simplex
Grootsnavelstern | Charrán picudo
The Large-billed Tern is a robust freshwater tern of the large rivers of South America, with a very thick yellow bill and a three-toned wing pattern. In the guide area it is a vagrant. Most records come from Panama, where the species has been reported repeatedly since the 1980s, sometimes with birds staying for weeks.
Voice
Loud, harsh, somewhat gull-like calls, lower than those of smaller terns; often given in flight.
Recording: JAYRSON ARAUJO DE OLIVEIRA — CC BY-NC-SA 4.0 · shortened to the first 60 s, mono · xeno-canto
Identification
37–39 cm, with a short, slightly forked tail. The bill is long, very thick and bright yellow. Cap and ear coverts are black, the forehead speckled white outside the breeding season. Back, inner wing coverts and tail are grey, the underparts white. In flight the wing pattern stands out: black primaries, a broad white triangle across the secondaries and greater coverts, and a grey forewing. The legs are yellowish. The sexes are alike. Juveniles have brown-scaled upperparts, a browner cap and a duller bill.
Confusion species
Sabine's Gull Xema sabini has a similar three-toned wing pattern, but is smaller, with a small black bill with a yellow tip and a deeply forked tail; it lives almost only at sea. Gull-billed Tern Gelochelidon nilotica has a short black bill and uniformly pale wings. Royal Tern Thalasseus maximus has an orange bill, a short crest and pale grey wings without a white triangle.
Habitat
In the guide area mainly freshwater lakes, rivers, marshes and rice fields in the lowlands, as well as coastal lagoons and river mouths. In its breeding range large rivers with sandbars, lakes and estuaries. It fishes by dropping into the water from a searching flight.
Where the bird is most at home, classified by the vegetation units of Mexico and Central America.
Range and movements
In Panama more than ten records since the 1980s, mainly in the provinces of Colón and Panamá, with further birds in Darién and Herrera; one of the sites is the La Jagua marsh. In Nicaragua a few birds in 2012 and 2013 on the Río San Juan and in the department of Granada on Lake Nicaragua. Outside the guide area the species breeds across most of South America east of the Andes, south to northern Argentina; as a vagrant also in the Caribbean, Bermuda and the United States.
How and when to look
Freshwater lakes and marshes in the lowlands of Panama are where a Large-billed Tern is most likely, often among other terns. In flight the black, white and grey wing pattern shows from afar; perched, the heavy yellow bill stands out.
Conservation status
Not threatened globally. The species is widespread along South American rivers; dams and changing water levels can affect breeding sites on sandbars. In the guide area a vagrant with no breeding records.
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. Phaetusa comes from Greek mythology: Phaethusa was a daughter of Helios and sister of Phaethon. simplex is Latin for 'simple, plain', after the plain plumage. The specimen the first description was based on came from Cayenne, French Guiana.