Twelve races of the Scrub Jay (Aphelocoma coerulescens) occupy a geographic range extending from southern Mexico northward over most of western North America to southern Washington and Idaho. Another race is isolated in central Florida (American Ornithologists’ Union 1957). Good quantitative information on nesting ecology is available only for the Florida race (A. c. coerulescens; Woolfenden 1973, 1975, Stallcup and Woolfenden 1978). Atwood (1978, 1980b) described the breeding biology of the Santa Cruz Island Scrub Jay (A. c. insularis), an insular population, but presented few quantitative data on nesting success. Anecdotal information on nesting by other races can be found in Bent (1946), Hardy (1961), Brown (1963), Stewart et al. (1972) and Verbeek (1973). This paper documents basic reproductive parameters of Scrub Jays (A. c. superciliosa) in the Sacramento Valley of northern California.