Betula nigra vs red birch

Betula nigra and red birch both are nouns.

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

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

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

Other synonyms of Betula nigra include black birch, river birch.

Betula nigra (noun)	red birch (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