Source : Webster's Revised Unabridged Dictionary (1913)

Sea bird \Sea" bird`\ (Zo["o]l.)
   Any swimming bird frequenting the sea; a sea fowl.

Source : WordNet®

sea bird
     n : a bird that frequents coastal waters and the open ocean:
         gulls; pelicans; gannets; cormorants; albatrosses;
         petrels; etc. [syn: {seabird}, {seafowl}]