To determine what kind of factors are implied in the decline of long-distance birds, knowledge on feeding ecology in breeding and wintering areas is essential. We present the first study recording the quantity and quality of food eaten by a population of black storks Ciconia nigra in the Africa wintering zone, as well as prey abundance in the field by testing an eventual foraging strategy based on the selection of biotic parameters of fish prey (body size, energy gain, swimming speed and fish armaments). Black storks preferentially selected two fish species of Siluriforms that were not the most abundant species in the field. Storks carried out interspecific selection according to the swimming speed of fish species and intraspecific selection depending on prey size, probably to avoid defensive armaments of the preferred fish prey. Small fishes consumed by the birds constituted 91% of the diet and 45% of the total food energy intake. Small fishes were more frequently caught than large ones, even if the storks sometimes took the opportunity to catch large fishes that provided a high energy gain. Energy assimilation of black storks is almost twofold higher than the estimated daily energy expenditure. This study suggests that the quantity of food would satisfy the energy requirements of the species during the winter in Africa, enable them to store reserves and ensure their survival in the African areas.