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Filip Tulis, Imrich Jakab, Roman Slobodník and Michal Hudec

Abstract

During the years 2010-2012, we observed the spatial activity of long-eared owls by the radio telemetry in an agricultural land. The average home range size of tracked long-eared owls for 100 and 95% minimum convex polygon (MCP) was 415.93 and 350 ha, respectively. Between the breeding and the non-breeding season, we did not record significant differences in the size of home ranges. Open land units (meadows and arable lands) belonged to the most abundant land units in the home ranges of tracked owls (mean for 100 and 95% MCP was 24.6 and 24.3%, respectively). Forest edges with their ecotone character also represented the abundant land unit (mean for 100 and 95% MCP was 11.4 and 10.6%, respectively). An amount of built-inhabited areas in home ranges (mean for 100 and 95% MCP was 8.2 and 10.1%, respectively) correlated positively with their size (Spearman rank correlation: for 100% MCP: rs = 0.83, p <0.05; for 95% MCP: rs = 0.91, p <0.05) that indicates long-eared owls to be avoiding built-inhabited areas as an area of the food getting. Two individuals of long-eared owl changed the winter roosts during one non-breeding season, which were at a distance of 650 m from each other.

Open access

Anton Krištín, Filip Tulis, Peter Klimant, Kristián Bacsa and Michal Ambros

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.

Open access

Roman Slobodník, Filip Tulis, Jozef Chavko and Jozef Lengyel

Abstract

The rook is a species inhabiting open agricultural landscape whose non-active nests are also used by other bird species for nesting. It is the decline in rook colonies that has been posited as one of the reasons for decrease in the red-footed falcon (Falco vespertinus) population in Slovakia since the 1970s. During the period from 2012 till 2016, four monitorings of rook colonies were carried out in south-western Slovakia (Diakovce, Nitrianska Osada, Sokolce and Tvrdošovce). In the colony at Tvrdošovce, supporting activity involving provisioning of rooks with nest material was under way from 2014 until 2016. While the colonies at Diakovce and Nitrianska Osada have been showing a slight decrease in the number of nesting rooks, despite larger interannual differences the colony at Sokolce has been showing an upward trend. The size of the colony at Tvrdošovce has been stable since the beginning of the supporting activity. This activity had a statistically significant positive effect on the width of rook nests. In 74 cases in the studied rook colonies we have recorded nesting by three other bird species – Eurasian kestrel (Falco tinnunculus) 43.8%, western jackdaw (Corvus monedula) 39.7% and long-eared owl (Asio otus) 16.4%. In 2015 two female redfooted falcons were observed in the colony at Tvrdošovce.

Open access

Filip Tulis, Roman Slobodník, Vladimír Langraf, Michal Noga, Zuzana Krumpálová, Zbyšek Šustek and Anton Krištín

Abstract

The red-footed falcon and Eurasian falcon represent two syntopical falcon species. While the Eurasian falcon is considered a common and numerous species in Slovakia, the red-footed falcon population has undergone a considerable decline during the past few decades. Nowadays it nests in a single locality in Slovakia, the Sysľovské polia Special Protection Area, which forms the northern and fragmented border of the species distribution area in Europe. By analysing prey remains from 9 nests (from 1998, 2001, 2013, 2014 and 2016), we identified 433 prey items belonging to 35 taxa and 9 orders. Every year, invertebrates made up the major part of the diet spectrum, in which Calosoma auropunctatum, Tettigonia viridissima, Zabrus tenebrioides, Anisoplia aegetum and Rhizotrogus sp. were the most frequent species of prey. Of the vertebrates, Microtus arvalis was the most hunted prey species. By supplementary analysis of 21 photos, we extended our knowledge on the diet by other 6 taxa. The peak of the M. arvalis population growth in 2014 did not manifest itself in the red-footed falcon diet composition. In 1998, 2014 and 2016 we also studied the diet of a syntopical species, the Eurasian kestrel. By analysing prey remains in 22 nests, we identified 1,151 prey items belonging to 37 taxa and 7 orders. In 1998 and 2014 vertebrates predominated, especially the common vole, however in 2016 invertebrates prevailed. This fact could be a reaction to the M. arvalis population peak in 2014 and its decline in 2016. These results suggest that this variability in the foraging behaviour of the Eurasian kestrel, an opportunistic predator, during the hunting of invertebrates increases the diet similarity and overlapping of the food niche of both studied falcon species.