true flycatcher vs oscine

true flycatcher and oscine both are nouns.

Word	Noun	Adjective	Verb	Adverb
true flycatcher	Yes	No	No	No
oscine	Yes	Yes	No	No

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

true 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 true flycatcher include oscine bird.

true 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

true flycatcher (adjective)	oscine (adjective)
	of or relating to the songbirds