oceanic bird vs sea bird

oceanic bird and sea bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
oceanic bird	Yes	No	No	No
sea bird	Yes	No	No	No

As nouns, sea bird is a hypernym of oceanic bird; that is, sea bird is a word with a broader meaning than oceanic bird:

oceanic bird: bird of the open seas
sea bird: a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.

Other hypernyms of oceanic bird include seabird, seafowl.

oceanic bird (noun)	sea bird (noun)
bird of the open seas	a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.