What is "sea tern"

Tern \Tern\ (t[~e]rn), n. [Dan. terne, t[ae]rne; akin to Sw. t["a]rna, Icel. [thorn]erna; cf. NL. sterna.] (Zo["o]l.) Any one of numerous species of long-winged aquatic birds, allied to the gulls, and belonging to Sterna and various allied genera.

Note: Terns differ from gulls chiefly in their graceful form, in their weaker and more slender bills and feet, and their longer and more pointed wings. The tail is usually forked. Most of the species are white with the back and wings pale gray, and often with a dark head. The common European tern ( Sterna hirundo) is found also in Asia and America. Among other American species are the arctic tern ( Sterna paradis[ae]a), the roseate tern ( Sterna Dougalli), the least tern ( Sterna Antillarum), the royal tern ( Sterna maxima), and the sooty tern ( Sterna fuliginosa).

Hooded tern. See Fairy bird, under Fairy.

Marsh tern, any tern of the genus Hydrochelidon. They frequent marshes and rivers and feed largely upon insects.

River tern, any tern belonging to Se["e]na or allied genera which frequent rivers.

Sea tern, any tern of the genus Thalasseus. Terns of this genus have very long, pointed wings, and chiefly frequent seas and the mouths of large rivers.