Does breeding habitat affect the amount of ants in the diet of European bee-eater nestlings?

European bee-eater (Merops apiaster Linnaeus, 1758; Coraciiformes: Meropidae) is known as a bee-predator, but its food spectrum is variable and depends on the current supply. This is the first study focused on the ants (Hymenoptera: Formicidae) as important prey in the diet of the European bee-eater. In 2017, 9,604 insect prey was obtained from pellets gained from two colonies breeding: (1) underground of a grazed sand dune (Radvaň nad Dunajom) and (2) in the sandy wall (Gabcikovo) without pasture, both in southern Slovakia. Five ant taxa were identified, the list of ants in the bee-eater’s diet was expanded by three taxa Lasius sp., Camponotus vagus (Scopoli, 1763) and Liometopum microcephalum (Panzer, 1798). In summary, ants represent the second most abundant family (12.35 %) of total prey. Compared to adults, nestlings (15.04 %) ate significantly more ants than adults (10.97 %). To study the ants’ composition in the diet of bee-eater near to different types of habitats, the pellets of nestlings were chosen because they more accurately reflect the sources of insect during the breeding season. Differences in the feeding of the European bee-eater nestlings between the grazed and the non-grazed locality were confirmed, where Lasius sp. and Tetramorium sp. highly correlated with grazing site. Moreover, nestlings ate significantly more ants in the area, where an open habitat was managed by grazing (6.55 vs. 15.04 %). The presented research indicates the importance of traditional pastures in the country for ants and also for bee-eaters. These ecosystem engineers are likely to find more microhabitats on the pastures, which has also been reflected in the diet of the nestlings breeding on the grazed site.