owl vs bird of night

owl and bird of night both are nouns.

Word	Noun	Adjective	Verb	Adverb
owl	Yes	No	No	No
bird of night	Yes	No	No	No

As nouns, owl and bird of night are synonyms defined as:

owl and bird of night: nocturnal bird of prey with hawk-like beak and claws and large head with front-facing eyes

Other synonyms of owl include bird of Minerva, hooter.

owl (noun)	bird of night (noun)
nocturnal bird of prey with hawk-like beak and claws and large head with front-facing eyes	nocturnal bird of prey with hawk-like beak and claws and large head with front-facing eyes