The noun has 2 meanings:
Meaning #1:
any new participant in some activity
Synonyms: newcomer, fledgling, starter, neophyte, freshman, entrant
Meaning #2:
young bird that has just fledged or become capable of flying
Synonym: fledgling
The adjective fledgeling has one meaning:
Meaning #1:
of a young bird just having acquired its flight feathers
Synonym: fledgling
