great grey owl vs Strix nebulosa

great grey owl and Strix nebulosa both are nouns.

Word	Noun	Adjective	Verb	Adverb
great grey owl	Yes	No	No	No
Strix nebulosa	Yes	No	No	No

As nouns, great grey owl and Strix nebulosa are synonyms defined as:

great grey owl and Strix nebulosa: large dish-faced owl of northern North America and western Eurasia

Other synonyms of great grey owl include great gray owl.

great grey owl (noun)	Strix nebulosa (noun)
large dish-faced owl of northern North America and western Eurasia	large dish-faced owl of northern North America and western Eurasia