black birch vs Betula nigra

black birch and Betula nigra both are nouns.

Word	Noun	Adjective	Verb	Adverb
black birch	Yes	No	No	No
Betula nigra	Yes	No	No	No

As nouns, black birch and Betula nigra are synonyms defined as:

black birch and Betula nigra: birch of swamps and river bottoms throughout the eastern United States having reddish-brown bark

Other synonyms of black birch include red birch, river birch.

black birch (noun)	Betula nigra (noun)
birch of swamps and river bottoms throughout the eastern United States having reddish-brown bark	birch of swamps and river bottoms throughout the eastern United States having reddish-brown bark
common birch of the eastern United States having spicy brown bark yielding a volatile oil and hard dark wood used for furniture