Cygnus atratus vs black swan

Cygnus atratus and black swan both are nouns.

Word	Noun	Adjective	Verb	Adverb
Cygnus atratus	Yes	No	No	No
black swan	Yes	No	No	No

As nouns, Cygnus atratus and black swan are synonyms defined as:

Cygnus atratus and black swan: large Australian swan having black plumage and a red bill

Cygnus atratus (noun)	black swan (noun)
large Australian swan having black plumage and a red bill	large Australian swan having black plumage and a red bill