Grinnell and Miller (1944) mapped the breeding range of the Red-breasted Sapsucker (Sphyrapicus ruber) in coastal California as extending south in Mendocino County to just below the Big River on the west and to Mt. Sanhedrin on the east (Figure 1).
The recent discovery of Red-breasted Sapsuckers breeding in coastal Marin County—about 165 km south of this limit (Laymon and Shuford 1980; Shuford 1985)—along with the knowledge of a number of recent unpublished breeding records from northern Sonoma County (B.D. Parmeter, pers. comm.) prompted me to investigate the extent of this apparent range extension.