gooney bird vs mollymawk

gooney bird and mollymawk both are nouns.

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

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

gooney bird: a variety of albatross with black feet
mollymawk: large web-footed birds of the Southern Hemisphere having long narrow wings; noted for powerful gliding flight

Other hypernyms of gooney bird include albatross.

gooney bird (noun)	mollymawk (noun)
a variety of albatross with black feet	large web-footed birds of the Southern Hemisphere having long narrow wings; noted for powerful gliding flight