stork vs policeman bird

stork and policeman bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
stork	Yes	No	No	No
policeman bird	Yes	No	No	No

As nouns, policeman bird is a hyponym of stork; that is, policeman bird is a word with a more specific, narrower meaning than stork:

stork: large mostly Old World wading birds typically having white-and-black plumage
policeman bird: large mostly white Australian stork

stork (noun)	policeman bird (noun)
large mostly Old World wading birds typically having white-and-black plumage	large mostly white Australian stork