Old World flycatcher vs flycatcher

Old World flycatcher and flycatcher both are nouns.

Word	Noun	Adjective	Verb	Adverb
Old World flycatcher	Yes	No	No	No
flycatcher	Yes	No	No	No

As nouns, Old World flycatcher and flycatcher are synonyms defined as:

Old World flycatcher and flycatcher: any of a large group of small songbirds that feed on insects taken on the wing

Other synonyms of Old World flycatcher include true flycatcher.

Old World flycatcher (noun)	flycatcher (noun)
any of a large group of small songbirds that feed on insects taken on the wing	any of a large group of small songbirds that feed on insects taken on the wing
	large American birds that characteristically catch insects on the wing