great grey owl vs hooter

great grey owl and hooter both are nouns.

Word	Noun	Adjective	Verb	Adverb
great grey owl	Yes	No	No	No
hooter	Yes	No	No	No

As nouns, hooter is a hypernym of great grey owl; that is, hooter is a word with a broader meaning than great grey owl:

great grey owl: large dish-faced owl of northern North America and western Eurasia
hooter: nocturnal bird of prey with hawk-like beak and claws and large head with front-facing eyes

Other hypernyms of great grey owl include bird of Minerva, bird of night, owl.

great grey owl (noun)	hooter (noun)
large dish-faced owl of northern North America and western Eurasia	nocturnal bird of prey with hawk-like beak and claws and large head with front-facing eyes
	a device on an automobile for making a warning noise
	informal terms for the nose