Optimal foraging in Bam Owls? Rodent frequencies in diet and fauna by Orlando A. Schwartz and Vernon C. Bleich. Bull. Southern California Acad. Sci., 84(l):41-45, 1985. We determined the frequencies of prey in the diet of Bam Owls by identifying mammal crania contained in pellets, and we determined the frequencies of prey items in the fauna by live and snap trapping. Data from two sites in Southern California showed approximately equal portions of prey in the diet and in the fauna. Such agreement may be expected when the predator perceives a low quality habitat, or it might be due to efficient predation methods that eliminate some of the constraints that face foraging predators.