Caspian Tern

How to find it

Start on the Pacific side, at the Gulf of Nicoya. A local birder found a Caspian Tern in the Chomes area, and the estuary and shrimp pond sites there are worth checking. High tide pushes birds into the ponds, so plan around the tide. Puntarenas is good for seawatching migrant terns. Scan every flock of Royal and Sandwich Terns for the one bird that is clearly bigger, with a deeper red bill. Freshwater marsh edges at Palo Verde are also worth a look.

How to recognise it

Start with size and bill. This is the largest tern in the world, and it carries a heavy red-orange bill with a dark tip.

The field marks, in plain terms:

- Cap: black.

- Body: white above and below, with pale gray wings.

- Legs: black on adults.

- In flight: the tail looks only slightly notched compared with other terns, and the undersides of the wingtips are dark.

- Non-breeding season: the black cap stays but shows white streaks on the forehead.

- Young birds: an orange bill and mottled gray and brown upperparts.

What it sounds like

Recording: Trinity Berry, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

It eats almost only fish. It flies with its bill pointed down, hovers when it spots prey, then plunge-dives and usually goes fully under the water.

It is less sociable than most terns and usually feeds alone or in small groups. So expect one bird among other terns rather than a big flock of its own kind. At Palo Verde National Park, one rested with Elegant, Royal and Gull-billed Terns at the edge of a marsh, which makes mixed tern flocks the pattern to scan.

Unlike most terns, it often flies overland on its way to and from wintering areas, which may help explain inland sightings at wetlands.

Where it lives

Worldwide the species uses both fresh and salt water. Typical places are coasts, estuaries, lagoons, marshes, lakes, large rivers and sheltered beaches.

In Costa Rica the records point to the Pacific side: the Gulf of Nicoya, the Tárcoles area on the Central Pacific coast in Puntarenas province, and Palo Verde National Park in Guanacaste, a wetland and dry forest park on the Pacific slope. It can turn up inland on freshwater wetlands as well as on the coast.

When to see it

North American Caspian Terns usually migrate south from August through October and north in April and May. Those dates cover the whole continent, so they only hint at when migrants might pass through Costa Rica.

Similar birds

Royal Tern looks similar but is smaller, with an orange-red bill, a more obvious shaggy crest and a paler underwing. The Caspian Tern is about 20 percent larger than a Royal Tern. In flight it can look like a large gull, but the red pointed bill and the black or blackish cap all year separate it from gulls.

Names and lore in Costa Rica

Costa Rican bird lists give the local Spanish name as Pagaza Mayor, with Piquirrojo (also written Piquirojo) as an alternate name that refers to the red bill.

Status and conservation

It is a migrant (M) on the AOCR list and is rated Least Concern globally.

Photography tips

High tide pushes birds into the shrimp ponds around Chomes, which can bring them closer. Look for the single large bird with the deep red bill among Royal and Sandwich Terns.