Old World flycatcher vs oscine

Old World flycatcher and oscine both are nouns.

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

As nouns, oscine is a hypernym of Old World flycatcher; that is, oscine is a word with a broader meaning than Old World flycatcher:

Old World flycatcher: any of a large group of small songbirds that feed on insects taken on the wing
oscine: passerine bird having specialized vocal apparatus

Other hypernyms of Old World flycatcher include oscine bird.

Old World flycatcher (noun)	oscine (noun)
any of a large group of small songbirds that feed on insects taken on the wing	passerine bird having specialized vocal apparatus

Old World flycatcher (adjective)	oscine (adjective)
	of or relating to the songbirds