mollymawk vs oceanic bird

mollymawk and oceanic bird both are nouns.

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

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

mollymawk: large web-footed birds of the Southern Hemisphere having long narrow wings; noted for powerful gliding flight
oceanic bird: bird of the open seas

Other hypernyms of mollymawk include pelagic bird.

mollymawk (noun)	oceanic bird (noun)
large web-footed birds of the Southern Hemisphere having long narrow wings; noted for powerful gliding flight	bird of the open seas