dark-eyed junco vs slate-colored junco

dark-eyed junco and slate-colored junco both are nouns.

Word	Noun	Adjective	Verb	Adverb
dark-eyed junco	Yes	No	No	No
slate-colored junco	Yes	No	No	No

As nouns, dark-eyed junco and slate-colored junco are synonyms defined as:

dark-eyed junco and slate-colored junco: common North American junco having grey plumage and eyes with dark brown irises

Other synonyms of dark-eyed junco include Junco hyemalis.

dark-eyed junco (noun)	slate-colored junco (noun)
common North American junco having grey plumage and eyes with dark brown irises	common North American junco having grey plumage and eyes with dark brown irises