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Descriotion Least terns (all currently recognized subspecies and populations) are the smallest members of the subfamily Sterninae and family Laridae of the order Charadriiformes, measuring about 21-24 em long with a 51 em wingspread. Sexes are alike, cha~acterized by a black-capped crown, white forehead, grayish back and 'dorsal wing surfaces, snowy white undersurfaces, legs of various o~ange and yellow colors depending on the sex, and a black-tipped bill whqse color also varies depending on sex (Watson 1966, Davis 1968, Boyd and Thompson 1985). Boyd and Thompson (1985) developed the following criteria'to distinguish the sexes in the field based upon their work in Kansas: 1) Females usually have a wing chord less than 171 mm long while males usually have a wing chord greater than 174 mm. 2) A male's feet are brighter, than its mate's feet; the male's are bright orange, while the fe~ale's feet are bright to pale yellow, or rarely grey., 3) A male's bill is larger thah the female's; the female's bill depth at its widest point is 4.5 mm to 5.5 mm, while the male's is 6.0 mm or greater. 4) A male's bill is orange to bright yellow, whereas the female's bill is light or dull yellow, or, straw-colored. Immature birds have darker pl~age than adults, a dark bill, and dark eye stripes on their white foreheads. Jackson (1976) described the developmental stages of least te~n chicks. Further details on plumage development and variation were pr~sented by Massey and Atwood (1978) and Thompson and Slack (1983). Taxonoll\Y The least tern (Sterna antillafum) in North America was described by Lesson in 1847 (Ridgway 1895, Amer~can Ornithologists' Union 1957, 1983). The least tern in interior North 'America was described later as a race (Sterna albifrons athalassos) of the Old World little tern (Sterna albifrons) (Burleigh and Lowery 1.942). Two other described New World races were the eastern or coastal least tern (Sterna albifrons antillarum), and the California least tern (Sterna albi~rons browni). The coastal least tern breeds slong the Atlantic and Gulf coasts and the California least tern breeds along the California coast. As a result of studies on vocal~zations and behavior of this group of terns in the Old and New Worlds, th~ American Ornithologists' Union (1983) now treats the New World least lterns as a distinct species, Sterna anti11arum. Subspecies of New World least terns recognized by the American Ornithologists' Union (1957, 1983) are the interior least tern (now Sterna antillarum athalassos), the eastern or coastal least tern (now Sterna antillarum antillarum), and the California least tern (now Sterna antillarum browni). 2