Birch of western United States resembling the paper birch but having brownish bark WordNet 3.0 & Open English WordNet

Betula occidentalis, the water birch or red birch, is a species of birch native to western North America, in Canada from Yukon east to Northwestern Ontario and southwards, and in the United States from eastern Washington east to western North Dakota, and south to eastern California, northern Arizona and northern New Mexico, and southwestern Alaska. Wikipedia

Red birch (Betula occidentalis). Wiktionary