ant bird vs antbird

ant bird and antbird both are nouns.

Word	Noun	Adjective	Verb	Adverb
ant bird	Yes	No	No	No
antbird	Yes	No	No	No

As nouns, ant bird and antbird are synonyms defined as:

ant bird and antbird: any of various dull-colored South American birds that feeding on ants some following army ant swarms

ant bird (noun)	antbird (noun)
any of various dull-colored South American birds that feeding on ants some following army ant swarms	any of various dull-colored South American birds that feeding on ants some following army ant swarms