SummaryThe diets of sympatric Barn OwlsTyto albaand Australian KestrelsFalco cenchroideson islands off the coast of Western Australia were studied by pellet analysis. House MiceMus domesticuscomprised the bulk of the diet of the Barn Owl (83% by volume), with other species of small mammals and birds constituting most of the remainder of the diet. In contrast, reptiles and insects were the major prey categories in the diet of the Australian Kestrel (38% and 39%, respectively, by volume), with small mammals and birds constituting 23%. The dietary differences between the two species reflect the diurnal hunting activity of the Australian Kestrel and nocturnal hunting, especially for mice, in the Barn Owl.