Athene noctua vs bird of night

Athene noctua and bird of night both are nouns.

Word	Noun	Adjective	Verb	Adverb
Athene noctua	Yes	No	No	No
bird of night	Yes	No	No	No

As nouns, bird of night is a hypernym of Athene noctua; that is, bird of night is a word with a broader meaning than Athene noctua:

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

Other hypernyms of Athene noctua include bird of Minerva, hooter, owl.

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