Sternula antillarum
Order Charadriiformes
Family Laridae
Subfamily Sterninae
Adult in summer.— Forehead white, enclosed by black lines from the eye to the bill; rest of top of head black; back, wings, and tail light pearl-gray; under parts white; bill bright yellow, tip blackish.
Adult in autumn.— Similar, but head grayish-white; bill dull yellowish.
Immature.— Like fall adult, but back spotted with brownish; bill blackish.
The Least Tern is a summer resident of southern New England and Long Island from May to September; it is local, and nowhere common. It breeds sparingly on the south shore of Martha’s Vineyard, and perhaps at Chatham on Cape Cod. Its cry has been described as a “shrill staccato yip, yip, yip” (Job). Its size distinguishes it from the Common Tern. The light pearl-gray of its back and wings distinguishes it from the occasional Sooty Tern that might occur on the same coast in August or September. The white border that separates the black cap from the bill is an excellent field-mark, but this must not be confused with the whitish forehead of the immature Common and Roseate Terns.
Hoffmann – A Guide to the Birds of New England and Eastern New York (1904)