Lesser Black-backed Gull

How to find it

Treat any sighting as a bonus rather than a target. Costa Rica is not known for gull watching, and the regular gulls are Laughing Gull, migrant Franklin's Gulls and various terns. Scan sandy shorelines, wetlands and marshes, since that is where the species feeds. Check gull groups for a dark-backed bird, then look at the legs: bright yellow points to an adult Lesser Black-backed Gull. If the bird is young, remember its legs are pinkish to yellowish and compare the tertials. Because a rare gull can vanish within days, fresh local reports matter more than any fixed plan.

How to recognise it

Adults have a dark slate-grey to black back and wings, a white head and underparts, and a yellow bill with a red spot near the tip. The legs are yellow, and that is the most useful mark of all: Herring and Great Black-backed Gulls have pink legs.

Young birds are scaly blackish-brown above and take four years to reach adult plumage. Their darker, unbarred inner flight feathers (tertials) help separate them from young Herring Gulls. A Costa Rican paper notes that at that young age the legs are pinkish to yellowish, a point to check when sorting similar young gulls.

Be careful with birds that look adult. Some gulls thought to be adults turned out to be third-summer birds. Look for brownish tones in the wing coverts, most visible when the wing is spread.

What it sounds like

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

Behaviour and diet

This is a sociable, opportunistic gull. It eats almost anything: fish, marine invertebrates, eggs and chicks, small mammals and scraps, and it often visits garbage dumps and reservoirs to feed and rest.

In Florida, Lesser Black-backed Gulls stopped on a beach in the afternoon while flying between a landfill and a night roost. They paid little attention to people, so binoculars were rarely needed. That comes from elsewhere in its range, not from Costa Rica.

Where it lives

Lesser Black-backed Gulls are tied to shorelines. They use sandy areas, wetlands and marshes to feed. In Costa Rica the records come from the coasts: Tortuguero on the Caribbean side and Tárcoles on the Pacific.

More widely, the species breeds on the Atlantic coasts of Europe and winters south to West Africa. It has increased greatly in North America, mostly along the east coast.

When to see it

The first Costa Rican record came in late February at Tortuguero, the day after a petrel was found there on February 25. The Tárcoles gull stayed for more than one day, but a blog post from late November 2023 said it had gone missing, which shows a visitor can leave quickly.

Similar birds

Great Black-backed Gull is the main look-alike. The Lesser is much smaller and slimmer, with yellow legs instead of pinkish ones and smaller white spots at the wing tips. Adults are told from Herring and Great Black-backed Gulls by bright yellow legs. Young birds can be confused with other young Larus gulls, and their pinkish to yellowish legs help rule out look-alikes with other leg colours.

Names and lore in Costa Rica

The Spanish name on the Costa Rican list is Gaviota Sombría, the same name used for the species in Spain and across Spanish-speaking regions.

Status and conservation

The AOCR list marks it accidental (A), and it is rated Least Concern worldwide.