red birch vs birch tree

red birch and birch tree both are nouns.

Word	Noun	Adjective	Verb	Adverb
red birch	Yes	No	No	No
birch tree	Yes	No	No	No

As nouns, birch tree is a hypernym of red birch; that is, birch tree is a word with a broader meaning than red birch:

red birch: birch of swamps and river bottoms throughout the eastern United States having reddish-brown bark
birch tree: any betulaceous tree or shrub of the genus Betula having a thin peeling bark

Other hypernyms of red birch include birch.

red birch (noun)	birch tree (noun)
birch of swamps and river bottoms throughout the eastern United States having reddish-brown bark	any betulaceous tree or shrub of the genus Betula having a thin peeling bark