WatchList Species Account for Gull-billed Tern (Sterna nilotica)

Qualifies for the list as a Declining Yellow List Species

Photo: © Scott Streit

Breeding at scattered localities in Europe, Africa, Asia and Australia, and the Americas, the Gull-billed Tern breeds in North America along the Atlantic and Gulf Coasts, the west coast of Mexico, and two saline sites in southern California—San Diego Bay and the Salton Sea; the latter is one of its few interior colonies. Rather than just depending on fish, it feeds also on insects, crabs, and even the chicks of other terns. It nests in mixed colonies of other terns and Black Skimmers but is almost never abundant at any of these sites. It nests in marshes but more often on sandy beaches or sandy barrier islands. In the Salton Sea it nests on smal islets, usually bare of vegetation.

Determining population trends is difficult, as inventories have been erratic, but the total North American population is low, with estimates at 5,400, exclusive of California. Recreational boating and other human disturbance, including development, are major causes of nest mortality. Limiting human interference would benefit the terns. Some colonies are subject to invasion by Herring and Great Black-backed gulls; culling gulls is a management tool to increase breeding success of the terns at these colonies.