The study of the diet of extreme specialist species can help to understand the selective pressures that modulate the trophic strategies of raptors. This article provides insight into the trophic strategy of a little-known top predator and allows for a better understanding of the selective pressures that shape its diet. We studied the diet of European honey-buzzards, a raptor specialized in the consumption of social wasp brood. The ratio of predator to prey biomasses is one of the highest among raptors. We studied some factors that affect the energy demand of pairs which influence the diet composition and the daily rate of prey delivery to the nest. We explore hypotheses about the role of native and exotic vespids in the diet and the influence of the number and age of nestlings on diet composition, daily rate of prey delivery, and size of combs delivered. We installed trail cameras in 24 honey-buzzards nests in north-western Spain in 2018-2021. We estimated the proportion and daily rate of delivery of native common-wasps (Vespula vulgaris), invasive Asian-hornets (Vespa velutina), reptiles, and birds and the honey-buzzard´s preferences for vespid species. We performed LMMs, GLMMs, and MLRMs to analyse relationships between response variables and predictors. We identified 4611 prey. Honey-buzzards mainly consumed vespids (82% of prey). Common-wasps and Asian- hornets were almost the only two vespids consumed. The invasive hornet was the second most important prey consumed, but common-wasps were preferred. Vespids were more important as the age and number of nestlings increased. Our results suggest that the honey-buzzard´s diet is the adaptive result of the conflict between being a median-sized insect-eating migratory nidicolous raptor and collecting enough morsels for the growth of its nestlings, supporting the prey size and ingestion rate hypothesis. We discuss implications of our findings for the management of the invasive wasp