The Gull-billed Tern (Gelochelidon nilotica) is a medium-sized tern that breeds in small, scattered, often ephemeral colonies, typically in habitat devoid of vegetation near marine waters or saline lakes. In North America, the species breeds along the Atlantic coast south of New York, the Gulf of Mexico, and the Pacific coast of California and Mexico. Its distribution has contracted from known historic range along the Atlantic Coast, but has expanded along the Pacific Coast. Range changes in Mexico are unknown due to fragmentary knowledge of historical colony locations, but some range contraction may have occurred.