Inca Tern

How to find it

Any sighting here would be a stroke of luck, so scan piers, docks and fishing boats with care. The Puntarenas to Paquera ferry is one place where an Inca Tern has been noted among the seabirds, and pelagic species are said to be easier to see from it. Look closely at perched terns for the red bill and white moustache. The Isla de Chira bird landed on a boat during a day of small-scale fishing, which suggests a tern that may approach working boats. Keep in mind that only a few vagrants have reached the country.

How to recognise it

Adults are slate-gray with a long white moustache plume curling down the cheek. The bill and legs are red, with bare yellow skin at the bill base. The wing has a white trailing edge, and the tail is black and forked.

Up close, the bill and feet are a deep coral red, and the long white whisker plumes curl down and flare out from the cheeks.

Young birds look quite different. They are purplish-brown, then brownish-gray, before reaching adult plumage. Their bills and legs start out dark and slowly turn red, so a young bird lacks the bright red bill of an adult.

Behaviour and diet

In its home range the Inca Tern forages near the coast for anchoveta and other small fish. It feeds by plunge-diving from low flight. It joins other seabirds on sandy beaches, so a stray might turn up among other birds on the shore.

At home it is also at ease around ports, perching on boats, docks and buildings. That matches the Costa Rican records, which include a bird on a pier rail and another on a fishing boat.

Where it lives

At home, the Inca Tern lives along the Humboldt Current coast of Peru and Chile. It nests on sea cliffs and guano islands, and also on piers and old barges. It joins other seabirds on sandy beaches.

In Costa Rica it is a stray rather than a resident. The records so far come from the Pacific side: the Guanacaste coast and the Gulf of Nicoya.

When to see it

The two earliest Costa Rican records fall in winter, on 30 December 2013 and 21 January 2014. These are single dated records, not a seasonal pattern.

Similar birds

From a distance the Inca Tern can be mistaken for a Grey Gull, especially a young bird. Check the structure, and on adults look for the bright red bill. Grey Gull is not a Costa Rican bird, so a gray seabird with a red bill here deserves a careful look.

Names and lore in Costa Rica

The Costa Rican Spanish name is Charrán Inca. Elsewhere in Spanish it is also called Gaviotín Inca or Gaviotín monja, the last being the Chilean name, and zarcillo is another name given.

Status and conservation

The Inca Tern is category A on the official Costa Rican list, a casual visitor, while the IUCN rates it Near Threatened across its whole range.

Photography tips

In its home range it is at ease around ports, perching on boats, docks and buildings, and the Costa Rican records fit that: one on a pier rail, one on a fishing boat. Piers, docks and working boats are the places to point a lens. Look for the red bill and white moustache plumes on any perched tern.