boatswain bird vs tropic bird

boatswain bird and tropic bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
boatswain bird	Yes	No	No	No
tropic bird	Yes	No	No	No

As nouns, boatswain bird and tropic bird are synonyms defined as:

boatswain bird and tropic bird: mostly white web-footed tropical seabird often found far from land

Other synonyms of boatswain bird include tropicbird.

boatswain bird (noun)	tropic bird (noun)
mostly white web-footed tropical seabird often found far from land	mostly white web-footed tropical seabird often found far from land