nestling vs youngster

nestling and youngster both are nouns.

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

As nouns, nestling and youngster are synonyms defined as:

Other synonyms of nestling include child, fry, kid, minor, nipper, shaver, small fry, tiddler, tike, tyke.

nestling (noun)	youngster (noun)
young bird not yet fledged	a young person of either sex
a young person of either sex