Western Burrowing Owls (Athene cunicularia hypugaea) are capable of laying up to 12 eggs in a single clutch (Haug et al. 1993). If the first nest attempted in a season fails, the female often lays a replacement clutch (Thomsen 1971, Wedgewood 1976). But rearing of a second brood after the fledging of a first brood (double brooding) is uncommon in this species (Millsap and Bear 1990, Gervais and Rosenberg 1999). In 2020, after 23 years of continuous monitoring of Burrowing Owls nesting around the southern periphery of San Francisco Bay at Shoreline Regional Wildlife Area in Mountain View, Santa Clara County, California, we confirmed double brooding for the first time. The Burrowing Owls were being supplementally fed with mice to assess whether such feeding during the breeding season increases their reproductive success; this experiment may have resulted in the double brood. However, this instance of double brooding occurred three years after supplemental feeding commenced.