true flycatcher vs Old World flycatcher

true flycatcher and Old World flycatcher both are nouns.

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

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

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

Other synonyms of true flycatcher include flycatcher.

true flycatcher (noun)	Old World 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