horse of the wood vs Tetrao urogallus

horse of the wood and Tetrao urogallus both are nouns.

Word	Noun	Adjective	Verb	Adverb
horse of the wood	Yes	No	No	No
Tetrao urogallus	Yes	No	No	No

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

Other synonyms of horse of the wood include capercaillie, capercailzie.

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