Status Review and Conservation Recommendations for the Gull-billed Tern (Gelochelidon nilotica) in North America. Biological Technical Publication

摘要

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. Two subspecies (G. n. aranea and G. n. vanrossemi) occur in North America. The current population of G. n. aranea in the United States is estimated to be approximately 3610 pairs, over 60% of which occur in Texas. The number of birds in Texas appears stable, but the number of individuals has declined in Maryland, Delaware, Virginia, North Carolina, Florida, and possibly Georgia. G. n. vanrossemi has 737 to 808 pairs breeding in western Mexico and southern California.