vireo vs red-eyed vireo

vireo and red-eyed vireo both are nouns.

Word	Noun	Adjective	Verb	Adverb
vireo	Yes	No	No	No
red-eyed vireo	Yes	No	No	No

As nouns, red-eyed vireo is a hyponym of vireo; that is, red-eyed vireo is a word with a more specific, narrower meaning than vireo:

vireo: any of various small insectivorous American birds chiefly olive-grey in color
red-eyed vireo: of northern North America having red irises and an olive-grey body with white underparts

vireo (noun)	red-eyed vireo (noun)
any of various small insectivorous American birds chiefly olive-grey in color	of northern North America having red irises and an olive-grey body with white underparts