Gull-billed Tern

How to find it

Scan mixed tern roosts at estuaries and mudflats, since the bird is usually resting or feeding with other gulls and terns. Check each tern for the thick black bill rather than looking for a different shape. A mudbank like the one at Golfo Dulce is a good place to scan. Do not limit yourself to the shore, because it hunts insects in the air, so watch over open ground and marsh edges too. The Puntarenas lighthouse point, where inner and outer Gulf of Nicoya waters mix, attracts many terns and gulls, and the Puntarenas-Paquera ferry can turn up seabirds. Palo Verde, with its marsh and floodplain, is worth a look as well.

How to recognise it

The key mark noted on a Costa Rican checklist is a thick black bill.

The bill is short, thick and all black, about half the length of the head, which gives the bird a gull-like look.

Breeding birds have a black cap.

Nonbreeding birds lose the cap and show a black patch behind the eye.

The bird sits with a rounded head and long legs on a sturdy body.

The wings are broad and rounder than those of a Sandwich Tern, a bird it matches in size and shape.

What it sounds like

Recording: Yves Bas, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

Unlike most terns, it rarely plunge-dives. Across its range it picks small fish off the water surface and often catches insects such as grasshoppers and dragonflies in flight. Its diet is broad and does not depend on fish: it takes insects, small crabs and other prey from the ground, the air or bushes.

It flies with slow, shallow, regular wingbeats on a straighter path than other terns, and it swoops to snatch prey from the water or from vegetation.

In Costa Rica it is usually found resting or feeding with other gulls and terns, for example on a mudbank at Golfo Dulce.

Where it lives

Costa Rican records come from several landscapes. Palo Verde National Park, in the northern Pacific lowlands of Guanacaste, is floodplain, marsh and tropical dry forest. Tortuguero lies on the Caribbean slope, Lake Arenal is inland, and Chomes and Golfo Dulce are on the Pacific side, the latter on the southern Pacific coast.

At Golfo Dulce the bird used river estuary mudflats and sandy areas.

On its wintering grounds across its range the species uses mudflats and sandbars by coastal lagoons, and it comes inland when flooded fields offer food.

When to see it

Older work (Stiles and Smith, 1980), cited in Birds of the World, says the species is present all year along the Pacific coasts of Costa Rica and Panama. Summering birds in nonbreeding plumage outnumber wintering ones.

Similar birds

The Sandwich Tern is close in size and shape, but the Gull-billed Tern has a short, thick, gull-like bill, broad wings, long legs and a sturdy body. Young Sandwich Terns have short bills and are often mistaken for it. In winter plumage the dark eye patch looks like that of a Forster's Tern, a species also on the Costa Rican list, and again the thick black bill tells them apart.

Names and lore in Costa Rica

The official Costa Rican Spanish name is Charrán Piquinegro, the name used for Costa Rica and Nicaragua. Other Spanish names listed for the species include Pagaza Piconegra, Gaviotín Pico Grueso, Gaviotín Pico Negro and Charrán Piquigordo.

Status and conservation

The official Costa Rican bird list gives Gull-billed Tern the status M, a migrant that is not a resident breeder in the country.

Photography tips

It flies with slow, shallow, regular wingbeats on a straighter path than other terns. It hunts insects in the air or swoops to snatch prey from the water surface or from vegetation, so watch over open ground and marsh edges as well as the shore.