Includes bibliography. / A study of the ecology of the Southern African Kestrel was made in two areas of differing topography in the Eastern Cape Province (32 °S) of South Africa. The main objectives of the study were to describe foraging parameters (behaviour-time budgets, hunting success and diet) and breeding parameters (clutch size, hatching and fledging success, nestling, fledging and post-fledging periods) of the Southern African Kestrel. These parameters were compared to those from studies made on the European Kestrel (Falco tinnunculus tinnunculus) in western Europe (53 °N) in an environment which fluctuates relatively more than the South African study sites. Predictions concerning foraging and breeding ecology made by life-history theory in stable and fluctuating environments prompted the erection of the following hypotheses which were examined in this study. 1. Common Kestrels (Falco tinnunculus) in relatively stable environments have a more consistent but lower foraging yield than those breeding in fluctuating environments. 2. Common Kestrels in relatively stable environments have lower reproductive rates (longer incubation, nestling and post-fledgling dependence periods, later age at first breeding and longer life-span) than those in fluctuating environments. Southern African Kestrels spent different proportions of time of the two main hunting methods used, perch- and hover-hunting, than the European Kestrel. Perch-hunting was the predominant hunting method used by the Southern African Kestrel compared to hover-hunting in the European Kestrel. Southern African Kestrels had a higher prey-capture success for both hunting techniques. However, daily food intake was lower in Southern African Kestrels because a high proportion of the diet consisted of small invertebrates. Average clutch size was smaller in the Southern African Kestrel than that of the European Kestrel and Southern African Kestrels fledged on average fewer young. However, incubation, nestling and post-fledging periods were within the range recorded for the European Kestrel. The hypothesis that Common Kestrels in relatively stable environments have lower foraging yields is supported by this study. Although results from this study suggest that food yields are more consistent in stable environments, it was unable to evaluate this adequately. The hypothesis that reproductive rates are lower in relatively stable environments is partly supported in this study, but more data are required for parameters such as incubation and nestling periods to confirm such trends.