<p>Understanding the dietary ecology of migratory raptors is critical in trophic ecology, especially under accelerating environmental change that alters prey availability. This study investigates the feeding ecology of Eleonora’s Falcon (<i>Falco eleonorae</i>) using stable isotope analysis of carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) in feathers collected from 19 individuals and associated prey remains in nests. The isotopic data revealed significant variation in adults, particularly elevated δ¹⁵N values in basal feather segments, indicating a dietary shift toward higher trophic-level prey, mainly migratory passerines, during post-breeding migration. Quantitative analysis showed that passerines constituted 83.8% of the falcons’ diet in this period, with the Common Whitethroat (<i>Curruca</i> <i>communis</i>), Common Nightingale (<i>Luscinia</i> <i>megarhynchos</i>), and Common Hoopoe (<i>Upupa</i> <i>epops</i>) being the most frequently consumed species, while insects accounted for only 16.2%. Isotopic differences among prey highlighted higher δ¹⁵N and δ³⁴S values in passerines compared to insects. These results suggest that Eleonora’s Falcon heavily depends on migratory passerines during chick-rearing, underscoring the species’ vulnerability to fluctuations in prey availability caused by environmental changes. The study enhances the understanding of the trophic ecology of Eleonora’s Falcon and calls for further research on the dynamics of migratory prey populations to inform conservation efforts.</p>