ivory-billed woodpecker vs ivorybill

ivory-billed woodpecker and ivorybill both are nouns.

Word	Noun	Adjective	Verb	Adverb
ivory-billed woodpecker	Yes	No	No	No
ivorybill	Yes	No	No	No

As nouns, ivory-billed woodpecker and ivorybill are synonyms defined as:

ivory-billed woodpecker and ivorybill: large black-and-white woodpecker of southern United States and Cuba having an ivory bill; nearly extinct

Other synonyms of ivory-billed woodpecker include Campephilus principalis.

ivory-billed woodpecker (noun)	ivorybill (noun)
large black-and-white woodpecker of southern United States and Cuba having an ivory bill; nearly extinct	large black-and-white woodpecker of southern United States and Cuba having an ivory bill; nearly extinct