water birch vs Western paper birch

water birch and Western paper birch both are nouns.

Word	Noun	Adjective	Verb	Adverb
water birch	Yes	No	No	No
Western paper birch	Yes	No	No	No

As nouns, water birch and Western paper birch are synonyms defined as:

water birch and Western paper birch: birch of western United States resembling the paper birch but having brownish bark

Other synonyms of water birch include Betula fontinalis, mountain birch, swamp birch, Western birch.

water birch (noun)	Western paper birch (noun)
birch of western United States resembling the paper birch but having brownish bark	birch of western United States resembling the paper birch but having brownish bark