thickhead vs true flycatcher

thickhead and true flycatcher both are nouns.

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

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

thickhead: Australian and southeastern Asian birds with a melodious whistling call
true flycatcher: any of a large group of small songbirds that feed on insects taken on the wing

Other hypernyms of thickhead include flycatcher, Old World flycatcher.

thickhead (noun)	true flycatcher (noun)
Australian and southeastern Asian birds with a melodious whistling call	any of a large group of small songbirds that feed on insects taken on the wing