puffin vs sea bird

puffin and sea bird both are nouns.

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

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

puffin: any of two genera of northern seabirds having short necks and brightly colored compressed bills
sea bird: a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.

Other hypernyms of puffin include seabird, seafowl.

puffin (noun)	sea bird (noun)
any of two genera of northern seabirds having short necks and brightly colored compressed bills	a bird that frequents coastal waters and the open ocean: gulls, pelicans, gannets, cormorants, albatrosses, petrels, etc.