dark-eyed junco vs junco

dark-eyed junco and junco both are nouns.

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

As nouns, junco is a hypernym of dark-eyed junco; that is, junco is a word with a broader meaning than dark-eyed junco:

dark-eyed junco: common North American junco having grey plumage and eyes with dark brown irises
junco: small North American finch seen chiefly in winter

Other hypernyms of dark-eyed junco include snowbird.

dark-eyed junco (noun)	junco (noun)
common North American junco having grey plumage and eyes with dark brown irises	small North American finch seen chiefly in winter