Following Phillip (1986) and Browning (1992) and described in the Cornell Birds of the World species account (Geupel and Ballard).:

Systematics History
C. f. rufula Ridgway, 1903 [type locality = Nicasio, Marin County, California].

Distribution
Coastal NW California, USA from Oregon border S to San Francisco Bay area.

Identification
Like C. f. phaea, but more rufescent overall with flanks rich tawny brown.