Species and subspecies limits in least terns

In their recent commentary, Patten and Erickson (1996) raised two issues: (1) the specific distinctness of the Least Tern (Sterna antillarum) from the Little Tern (S. albifrons) and (2) the subspecific name(s) to be applied to breeding populations of Least Terns in coastal western Mexico. Here I briefly summarize evidence supporting the separation of Least and Little Terns and make a case for considering all populations of Least Terns on the west coast of the Americas as one subspecies (browni) until and unless field studies indicate otherwise.