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Inca Tern | Larosterna inca
Incastern | Charrán inca
The Inca Tern is a dark grey tern with white moustache plumes from the cold Humboldt Current along the west coast of South America. In the guide area it is a vagrant. There are scattered records from the Pacific coast of Panama and Costa Rica, and in some years, such as 2016 and 2026, several birds appeared at once.
Voice
A short, mewing or grating keek and a nasal cackling, especially from groups.
Recording: Cristian Pinto Fernandez — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
39–42 cm, with a forked tail. The plumage is plain slate-grey, darker on the head, with a narrow white trailing edge to the secondaries. A long white moustache plume curls down below the eye from the base of the bill. Bill and legs are bright red, with a yellow fleshy wattle at the gape. The sexes are alike. Juveniles are browner, with a dark bill, and have no or only a short moustache.
Confusion species
Brown Noddy Anous stolidus is brown with a whitish crown, a black bill, black legs and a wedge-shaped tail, without a white moustache. Black Noddy Anous minutus is blackish-brown with a white cap and a thin black bill. No other tern in the guide area combines dark grey plumage with a red bill and white moustache plumes.
Habitat
Coastal waters and rocky shores, harbours, piers and islets. It fishes by short plunge-dives or by picking prey from the surface in flight, often together with cormorants, pelicans and marine mammals that drive shoals of fish to the surface. In its breeding range it nests in holes and crevices in cliffs, on guano islands and even in harbour structures.
Where the bird is most at home, classified by the vegetation units of Mexico and Central America.
Range and movements
In Panama scattered records along the Pacific coast since 1983, including the provinces of Panamá, Veraguas, Los Santos and Chiriquí; in Costa Rica records in the province of Puntarenas; in 2019 also a report from the department of Escuintla in Guatemala. Most birds were seen from May to September. Outside the guide area the species breeds along the coast of Peru and Chile, and also occurs in Ecuador.
How and when to look
Piers, harbours and rocky shores along the Pacific coast of Panama and Costa Rica are the places to watch for this species, especially in years when Inca Terns appear further north than usual. The dark grey bird with a red bill and white moustache is unmistakable.
Conservation status
Near Threatened. The population fluctuates strongly with the food supply in the Humboldt Current, which collapses in El Niño years. Disturbance and guano extraction on breeding islands, introduced predators and competition with the anchovy fishery are further threats.
Scientific name
Larosterna inca | (Lesson & Garnot, 1827)
Lesson & Garnot described the species in 1827 as Sterna Inca; because it was later moved to another genus, the author and year stand in brackets. The genus Larosterna was introduced in 1852 by Blyth. Larosterna combines the genus names Larus 'gull' and Sterna 'tern': a 'gull-tern'. inca refers to the Inca, after the bird's range along the coast of Peru. The specimen the first description was based on came from Lima, Peru.