"Sterna (T.) cantiaca. Sandwich Tern. Ducal Tern. Bill black, the tip 1/2 to 3/4 an inch bright yellow, sharply defined against the black; "inside of mouth deep blue." Feet dull black. Pileum and occipital crest glossy black, with a tinge of green; the color extending just below the eyes, but leaving a space along the side of the mandible white to the extremity of the feathers. Mandible exceedingly light pearly-blue, fading on the rump and upper tail-coverts into pure white; but the rectrices themselves have a slight shade of pearly-bluish. Primaries colored as in maxima. On the inner web of the first the black space is broad and deep in color; when about 1& 1/2 inches from the apex of the quill it quite suddenly grows wider, so as to exclude the white portion from the tip altogether. The second, third, and fourth primaries have the same general pattern, but he white runs up further on the central portion than on the edge of the web, so that toward its end it receives a narrow edging of blackish. The other primaries have no blackish, but are simply pearl-blue, with broad white margins along the whole length of heir inner webs. The outer primaries are all heavily silvered when the quills are new.
aerial diving birds, aquatic feeding birds, birds, Ducal Tern, migratory birds, North American birds, ornithology, Sandwich Tern, seabirds, Sterna (T.) cantiaca, Sterna sandvicesis, Thalasseus sandvicensis
Elliot Coues Key to North American Birds (Boston, MA: Estes and Lauriat, 1884)