Belcher's Gull is distributed along that part of the Pacific coast of South America that is influenced by the Humboldt Current, i.e. between northern Peru and northern Chile though it does disperse to northern Ecuador and central Chile.

It is found on rocky shores and offshore islands where it feeds on fish, shellfish and carrion.

Second year birds (photo 5) have a blackish mantle and a black tip to the bill with duller legs while juveniles (photo 6) have a dark brown hood and breast with pale fringes to the upperparts.