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.Abstrakt: Potravná ponuka v hniezdnych teritóriách druhov hrá kľúčovú úlohu pre zloženie potravy druhov a ich hniezdny úspech. Sokol kobcovitý (Falco vespertinus) loví prevažne väčšie druhy hmyzu, dopĺňané menšími stavovcami. V hniezdnom období rokov 2014 a 2016 bola na piatich historických hniezdiskách druhu na Slovensku sledovaná jeho potravná ponuka so zameraním na Orthoptera, Mantodea, Rodentia a Eulipotyphla. Na poslednom aktívnom hniezdisku sa študovalo aj zastúpenie týchto skupín v potrave. Celkovo sme zaznamenali 45 druhov Orthoptera (z toho 23 druhov je známych ako potrava sokola kobcovitého), jeden druh Mantodea, 10 druhov Rodentia (z toho 2 druhy sú známe ako potrava sokola kobcovitého) a 5 druhov radu Eulipotyphla. Z hľadiska potravnej ponuky bola v oboch rokoch najvhodnejšia lokalita Tvrdošovce, ktorá kontinuálne vykazovala najvyššie druhové bohatstvo a abundanciu jednotlivých druhov. V medziročnom porovnaní hmyz vykazoval menšiu variabilitu početnosti ako drobné cicavce. V roku 2014 totiž vrcholila gradácia populácie hraboša poľného (Microtus arvalis), ktorá s výnim-kou jednej lokality (Bodza) zaznamenala v roku 2016 prepad po...

Diet composition of syntopically breeding falcon species Falco vespertinus and Falco tinnunculus in south-western Slovakia

“…In our studied nesting locality, the Sysľovské polia SPA, growth in the population of the common vole culminated in summer 2014 (Krištín et al 2017), however this culmination did not manifest itself in the red-footed falcon diet, and we did not even record a single instance of common vole in its diet in that year. By contrast, Bezzel & Hölzinger (1969) recorded an increased representation of common voles in the redfooted falcon diet just in the time of the culminating populations of common vole and field vole (Microtus agrestis).…”

“…However, in 2016 we found a lower proportion of vertebrates in Slovakia as well, and invertebrates thus represented a major part of the diet. It was just the year 2016 that was characterized by a decrease in the number of common voles in the studied locality when compared to 2014 (Krištín et al 2017), and the decrease in common vole availability could thus have been compensated by increased predation of invertebrates. This type of functional response, by which in reaction to a decrease in the number of common voles the Eurasian kestrel is able to switch to hunting insects, has been described by several researchers (Holling 1965, Korpimäki 1985.…”