railbird vs rooter

railbird and rooter both are nouns.

Word	Noun	Adjective	Verb	Adverb
railbird	Yes	No	No	No
rooter	Yes	No	No	No

As nouns, rooter is a hypernym of railbird; that is, rooter is a word with a broader meaning than railbird:

railbird: a fan of racing who watches races from the outer rail of the track
rooter: an enthusiastic devotee of sports

Other hypernyms of railbird include fan, sports fan.

railbird (noun)	rooter (noun)
a fan of racing who watches races from the outer rail of the track	an enthusiastic devotee of sports