Subspecies of the Least Tern in Mexico

Abstract

Debate about the validity of the subspecies of the Least Tern (Sterna antillarum) has been contentious and confusing, and a recent paper by Garcia and Ceballos describing Least Terns nesting in Jalisco, Mexico, has further confused the issue. Although their article makes a valuable contribution in documenting nesting of the Least Tern in Jalisco, their taxonomic treatment is misleading. Not only did they extend the known breeding range of S. a browni, the California Least Tern, hundreds of kilometers to the south of its described range, they called the subspecific status of S. a. browni "well-defined," yet called S. a. mexicana and S. a. staebleri, the only two subspecies known to breed in mainland Mexico, "uncertain" (presumably with regard to taxonomy). We strongly question their taxonomic assignment of the breeding Least Terns in Jalisco, which seems to be based only on their dismissal of mexicana and staebleri as valid taxa.