seafowl vs aquatic bird

seafowl and aquatic bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
seafowl	Yes	No	No	No
aquatic bird	Yes	No	No	No

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

seafowl: a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.
aquatic bird: wading and swimming and diving birds of either fresh or salt water

seafowl (noun)	aquatic bird (noun)
a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.	wading and swimming and diving birds of either fresh or salt water