nestling vs juvenile

nestling and juvenile both are nouns.

Word	Noun	Adjective	Verb	Adverb
nestling	Yes	No	No	No
juvenile	Yes	Yes	No	No

As nouns, juvenile is a hypernym of nestling; that is, juvenile is a word with a broader meaning than nestling:

Other hypernyms of nestling include juvenile person.

nestling (noun)	juvenile (noun)
young bird not yet fledged	a young person, not fully developed
a young person of either sex

nestling (adjective)	juvenile (adjective)
	of or relating to or characteristic of or appropriate for children or young people
	displaying or suggesting a lack of maturity