Trophic ecology of the Lesser Kestrel (Falco naumanni Fleischer, 1818) during the breeding season in Azerbaijan

The Lesser Kestrel (Falco naumanni) is an opportunistic predator, its trophic ecology in Azerbaijan has not been previously investigated. This study provides the first quantitative assessment of the diet composition of a breeding colony (comprising 12 pairs) utilizing anthropogenic structures at the Varvara Reservoir, Azerbaijan, between May and July 2020. Prey remains and regurgitated pellets (n = 42) were systematically collected from nests, perches, and communal foraging areas (mean prey items per pellet: 4.64 ± 2.13). Morphological analysis of 195 prey individuals revealed 19 species across four taxonomic classes. Mammals constituted the dominant dietary component (50.3%, n = 98), followed by insects (41.5%, n = 81), reptiles (5.1%, n = 10), and avian species (3.1%, n = 6). The Libyan Jird (Meriones libycus; 11.8% of individuals, 19.4% of biomass), Stein's Wood Mouse (Sylvaemus witherbyi; 10.3%, 16.8%), Social Vole (Microtus socialis; 9.7%, 16.0%), and House Mouse (Mus musculus; 10.3%, 16.8%) were the most frequently consumed mammalian taxa, collectively representing 83.7% of mammalian prey and 42.1% of the total diet. Among insects, orthopterans (Saga pedo, Locusta migratoria) and coleopterans (Melolontha melolonthus, Broscus cephalotes) were the predominant prey, comprising 50.6% of insect remains. Although numerically abundant, insects contributed only 6.5% to the estimated biomass, whereas vertebrates collectively accounted for 93.4% of the total biomass. Dietary niche breadth indicated moderate specialization (Simpson's B = 5.21). Insect consumption significantly increased during the nestling provisioning period (χ² = 43.0, p < 0.001), coinciding with the expected peak in regional insect phenology. These findings demonstrate an atypical vertebrate-dominated diet for this colony compared to most European and Asian populations, where insects typically constitute 70-99% of prey items. This pattern strongly supports the hypothesis that small mammals are locally abundant in this heterogeneous agricultural landscape. The persistent occupancy of the site (2004-2025) suggests that the colony persists under current trophic conditions, although further data on breeding success are required to accurately evaluate population viability. Ultimately, this study underscores the species' remarkable ecological plasticity in anthropogenic habitats.