REFINED COLORIMETRY VALIDATES ENDANGERED SUBSPECIES OF THE LEAST TERN

In contrast to the results of Thompson et al. (1992), refined colorime try validates three subspecies of Least Tern in North America, Sterna antillarum antillarum (Lesson), S. a. browni Mearns, and S. a. athalas sos Burleigh and Lowery. Four of nine color characters exhibited signi ficant seasonal differences, presumably a result of plumage wear and b leaching. The sexes differed in lightness and hue of dorsum and hind n eck. Males of S. a. athalassos differed significantly from those of bo th S. a. antillarum and S. a. browni in lightness of dorsum, and males of S. a. browni differed significantly from those of S. a. antillarum in lightness of hind neck. Females generally showed patterns concorda nt with males. Because S. a. browni and S. a. athalassos are listed as endangered, the validity of these taxa is important to conservationis ts and managers. Rigorous systematic methodology and scientific collec tions of high quality are indispensable to conservation biology.