gaviiform seabird vs seabird

gaviiform seabird and seabird both are nouns.

Word	Noun	Adjective	Verb	Adverb
gaviiform seabird	Yes	No	No	No
seabird	Yes	No	No	No

As nouns, seabird is a hypernym of gaviiform seabird; that is, seabird is a word with a broader meaning than gaviiform seabird:

gaviiform seabird: seabirds of the order Gaviiformes
seabird: a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.

Other hypernyms of gaviiform seabird include sea bird, seafowl.

gaviiform seabird (noun)	seabird (noun)
seabirds of the order Gaviiformes	a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.