arrival vs early bird

arrival and early bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
arrival	Yes	No	No	No
early bird	Yes	No	No	No

As nouns, early bird is a hyponym of arrival; that is, early bird is a word with a more specific, narrower meaning than arrival:

Other hyponyms of arrival include latecomer, newcomer.

arrival (noun)	early bird (noun)
accomplishment of an objective	a person who gets up very early in the morning
the act of arriving at a certain place	a person who arrives early before others do
someone who arrives (or has arrived)