Bridled Tern

How to find it

Look for it around floating seaweed patches (Sargassum) and other drifting debris at sea, where it forages for fish, squid and other small prey. Boat trips over warm coastal waters give the best chance. From land, seawatching works too. Scan flocks of distant terns carefully with a scope, because it can be missed among them. Look for a darker gray back and a hint of a head pattern.

How to recognise it

Start with size and shape: a medium-sized tern, about 36 cm long, with a dark back and a deeply forked tail. Breeding adults show a black crown and a black line from the bill to the eye. The bill and legs are black.

A pale nape collar and a thin white forehead patch that extends into a short eyebrow stripe help separate it from the Sooty Tern. Outside the breeding season the crown is mostly white with black streaks at the back. Young birds look like non-breeding adults but are paler above, with a scaly look. The Pacific form nelsoni has a darker back than other forms.

What it sounds like

Recording: bitsandbugs, CC0 1.0, source, read 4 Nov 2026.

Behaviour and diet

Birds are usually alone or in small, loose groups. At sea it rarely feeds in big flocks and stays close to floating debris, especially floating sargassum seaweed. It nests in sheltered crevices.

It feeds mostly by flying low, hovering and dipping to pick items off the water surface, and it seldom plunge-dives. It may gather where predatory fish drive small fish to the surface.

Where it lives

In Costa Rica it nests or rests on rocky islands just off the coast. It breeds on islands off the north Pacific coast, and one Costa Rican paper reports nesting among bunchgrass above sea cliffs, with cardón cacti nearby. Possible or known nesting areas include Santa Catalina Island in the southern Gulf of Papagayo and the islands around the Santa Elena Peninsula. The subspecies nelsoni breeds on islets including some in Guanacaste, in the northwest. Off the Caribbean coast it is an occasional visitor, and the nearest nesting colonies are off Belize and Venezuela.

When to see it

It is a breeding resident on the north Pacific islands, mostly from March to April and up to September. At other times it is rare or only occasional there, though a study off the Pacific coast found scattered birds in every season, usually fairly close to shore. Off the Caribbean coast it appears mostly between August and September.

Similar birds

The Sooty Tern is the usual comparison. The Bridled is slimmer and a little paler on the back, with a whitish collar across the hindneck, and in flight it shows more white in the outer tail and under the wingtip. It tends to nest in more scattered colonies and is more likely to be seen close to land.

Status and conservation

The AOCR list marks it as a rare resident and a migrant (RR,M), while globally it is rated Least Concern.

Photography tips

Use a scope on distant tern flocks and look for the darker gray back and a hint of a head pattern. Drifting seaweed patches are where it is most likely to settle or forage.