Food supply (Orthoptera, Mantodea, Rodentia and Eulipotyphla) and food preferences of the red-footed falcon (Falco vespertinus) in Slovakia

Abstract Food supply in the nesting territories of species has a key role to the species diet composition and their breeding success. Red-footed falcon (Falco vespertinus) preys predominantly on larger insect species with a supplementary portion of smaller vertebrates. In the breeding periods 2014 and 2016 their food supply, focusing on Orthoptera, Mantodea, Rodentia and Eulipotyphla, was analysed at five historical nesting sites of the species in Slovakia. Preference for these prey groups in the diet was also studied at the last active nesting site in this country. Overall we recorded 45 Orthoptera species (of which 23 species are known as the food of the red-footed falcon), one species of Mantodea, 10 species of Rodentia (of which 2 species are known as the food of the red-footed falcon) and 5 species of the Eulipotyphla order in the food supply. With regard to the availability of the falcons' preferred food, in both years the most suitable was the Tvrdošovce site, which continuously showed the greatest range and abundance of particular species. In the interannual comparison the insects showed lower variability in abundance than the small mammals. In 2014 the growth of the common vole (Microtus arvalis) population culminated and with the exception of a single site (Bodza) a slump in abundance was recorded in 2016. In comparing the diet composition with the food supply at the last Slovak breeding site Rusovce (Special Protection Area Sysľovské polia), we recorded significant preference for grasshopper Caliptamus italicus (in 2014), common vole (in 2016) and cricket Tettigonia viridissima (in both years) in the falcons' diet. They did not prey on the Apodemus sylvaticus species belonging among the abundant small mammal species in that locality. Conservation measures in the agricultural landscape are discussed in relation to homogeneous red-footed falcon breeding territories.