The diet of the Australian Kestrel Falco cenchroides was studied from castings and remains of food collected during nesting, from contents of digestive tracts and from castings collected during a plague of mice. Spiders, centipedes and, in particular, insects were taken in large numbers and composed most of the diet by number. Grasshoppers and crickets, followed by beetles and moths in various developmental stages, were the most common and regular insects. Small reptiles, small birds and mice made up the vertebrate component of the diet. Mice became the major prey during a plague.