The red kite (Milvus milvus) is a bird of prey that has seen its numbers decrease in a large part of Europe to such an extent that it has been classified "borderline threatened" by the IUCN. Curiously, this is not the case in Belgium where the numbers have been increasing for over 30 years. The aim of this work is to determine the factors responsible for the growth of red kite populations in the eastern cantons of Belgium. It is devoted, on the one hand, to the study of the diet of the kites during the breeding period, through the analysis of the contents of pellets and prey remains found in and around 176 kite nests and, on the other hand, to the study of a potential association between the diet and the reproductive success of the pairs.