horse of the wood vs capercaillie

horse of the wood and capercaillie both are nouns.

Word	Noun	Adjective	Verb	Adverb
horse of the wood	Yes	No	No	No
capercaillie	Yes	No	No	No

As nouns, horse of the wood and capercaillie are synonyms defined as:

Other synonyms of horse of the wood include capercailzie, Tetrao urogallus.

horse of the wood (noun)	capercaillie (noun)
large black Old World grouse	large black Old World grouse