Owl Prey Research Articles

Grasshoppers do not flee from their alarmed predators but from non-alarmed ones.

Alarm calls produced by basal prey have a well-known informative value. In multi-predator communities, mesopredators, when faced with top predators, may emit alarm calls that could inform basal prey about their lowered predation risk. To test this unexplored possibility, we conducted one field and one mesocosm experiment in which we simulated alarm and non-alarm calls from little owls (Athene noctua) as mesopredators and measured their effects on grasshoppers as prey of little owls but not of top predators. In the field experiment, we found that grasshopper species were significantly more abundant in patches where we simulated either the presence of scared little owls (alarm treatment) or no owls (control treatment) compared to patches where the presence of non-scared little owls (non-alarm treatment) was simulated. In the mesocosm experiment, locusts (Locusta migratoria) moved significantly more to exposed areas when we simulated the presence of scared little owls (alarm treatment) or of a granivorous bird (control treatment), while they moved to sheltered areas when we simulated the presence of non-scared owls (non-alarm treatment). These results show that prey could cue on predators' calls to assess their predation risk and make decisions, revealing unprecedented potential ecological consequences of alarm calls in invertebrate communities.

First data on the short-eared owl (Asio flammeus) prey in Patagonia (Argentina)

First data on the short-eared owl (Asio flammeus) prey in Patagonia (Argentina)

New records of small mammals in the diet of the buff-fronted owl, Aegolius harrisii and the black-and-white owl, Strix nigrolineata, along with a review of mammal prey of owls in Colombia

La dieta de los búhos y lechuzas de Colombia ha sido escasamente estudiada. El consumo de murciélagos y otros pequeños mamíferos ha sido registrado para Aegolius harrisii y Strix nigrolineata en otros países de Centro y Sudamérica; sin embargo, no había información sobre el tema para Colombia. Presentamos nuevas observaciones de la depredación de mamíferos por búhos en Colombia y una breve revisión de registros históricos. Reportamos el intento de consumo de un murciélago del género Platyrrhinus por parte del búho bicolor (Aegolius harrisii) y la presencia de murciélagos (Dermanura y Rhogeessa) y musarañas (Cryptotis) en una egagrópila del búho carinegro (Strix nigrolineata), en los Andes de Colombia. La revisión de la literatura y datos de colecciones biológicas arrojó un total de al menos 30 especies de mamíferos que han sido registradas en la dieta de 8 especies adicionales de búhos en el país. Los roedores son las presas con mayor número de reportes, que incluyen taxa de bosques, áreas urbanas y periurbanas. Esta información puede ser útil para estudios posteriores sobre los posibles efectos de la pérdida del hábitat en el consumo de mamíferos por búhos y su papel como controladores de hospederos de agentes zoonóticos.

Influence of prey availability on habitat selection during the non-breeding period in a resident bird of prey

BackgroundFor resident birds of prey in the temperate zone, the cold non-breeding period can have strong impacts on survival and reproduction with implications for population dynamics. Therefore, the non-breeding period should receive the same attention as other parts of the annual life cycle. Birds of prey in intensively managed agricultural areas are repeatedly confronted with unpredictable, rapid changes in their habitat due to agricultural practices such as mowing, harvesting, and ploughing. Such a dynamic landscape likely affects prey distribution and availability and may even result in changes in habitat selection of the predator throughout the annual cycle.MethodsIn the present study, we (1) quantified barn owl prey availability in different habitats across the annual cycle, (2) quantified the size and location of barn owl breeding and non-breeding home ranges using GPS-data, (3) assessed habitat selection in relation to prey availability during the non-breeding period, and (4) discussed differences in habitat selection during the non-breeding period to habitat selection during the breeding period.ResultsThe patchier prey distribution during the non-breeding period compared to the breeding period led to habitat selection towards grassland during the non-breeding period. The size of barn owl home ranges during breeding and non-breeding were similar, but there was a small shift in home range location which was more pronounced in females than males. The changes in prey availability led to a mainly grassland-oriented habitat selection during the non-breeding period. Further, our results showed the importance of biodiversity promotion areas and undisturbed field margins within the intensively managed agricultural landscape.ConclusionsWe showed that different prey availability in habitat categories can lead to changes in habitat preference between the breeding and the non-breeding period. Given these results we show how important it is to maintain and enhance structural diversity in intensive agricultural landscapes, to effectively protect birds of prey specialised on small mammals.

Distribution of Four Vole Species through the Barn Owl Tyto alba Diet Spectrum: Pattern Responses to Environmental Gradients in Intensive Agroecosystems of Central Greece.

Voles are the most common vertebrate pests in European agriculture. Identifying their distribution and abundance patterns provides valuable information for future management. Barn Owl diet analysis is one of the optimum methods used to record small mammal distribution patterns on large spatial scales. From 2003 to 2005, a total of 10,065 Barn Owl pellets were collected and analyzed from 31 breeding sites in the largest agroecosystem in Greece, the Thessaly plains. A total of 29,061 prey items were identified, offering deep insight into small mammal distribution, specifically voles. Four discrete vole species (Harting's vole Microtus hartingi, East European vole Microtus levis, Thomas's pine vole Microtus thomasi, and Grey dwarf hamster Cricetulus migratorius) comprised 40.5% (11,770 vole prey items) of the total Barn Owl prey intake. The presence and abundance of the voles varied according to underlying environmental gradients, with soil texture and type playing a major role. M. levis showed no significant attachments to gradients, other than a mild increase in Mollisol soils. It was syntopic in all sites with M. hartingi, which was the dominant and most abundant small mammal species, preferring non-arable cultivated land, natural grasslands, set-aside fields, and fallow land. M. thomasi was strictly present in western Thessaly and strongly associated with a sandy-clay soil texture and Alfisol soils. C. migratorius was the least represented vole (162 items), exclusively present in eastern Thessaly and demonstrating a stronger association with cereals, Mollisol soils, and an argillaceous-clay soil texture. This is the first study in Greece at such a large spatial scale, offering insights for pest rodents' distribution in intensive agroecosystems and their response to environmental gradients including soil parameters.

Herpesvirus Infection in a Breeding Population of Two Coexisting Strix Owls.

Simple SummaryAlthough infection with herpesvirus in owls has commonly been described as a highly lethal disease, there is very little information about the presence of herpesvirus and its potential impact in living owls in wild populations. Our study detected herpesvirus in a breeding population of Ural owls, which showed no clinical signs of illness nor productivity deviances (i.e., in clutch and brood size). Herpesvirus was detected in Ural owl adults and chicks, but not in a young tawny owl (despite the fact that they were in same nest and in persistent contact). Furthermore, herpesviruses were also detected in yellow-necked mice as both owls’ main prey. However, comparison of the herpesviruses detected showed that different herpesviruses are present in the owls and mice. The results of this study show that herpesvirus may be present in a Ural owl breeding population without any consequences on health and breeding performance. However, in the case of tawny owls, it seems that they are not susceptible to infection, which could be related to their polymorphism. It seems that small rodents are not a source of herpesvirus infection in owls and that the probable herpesvirus transmission pathway takes place intraspecifically, mostly from adults to young.Birds are a frequent host of a large variety of herpesviruses, and infections in them may go unnoticed or may result in fatal disease. In wild breeding populations of owls, there is very limited information about the presence, impact, and potential transmission of herpesvirus. The herpesvirus partial DNA polymerase gene was detected using polymerase chain reaction in oropharyngeal swabs of 16 out of 170 owls examined that were captured in or near nest boxes. Herpesvirus was detected in Ural owls (Strix uralensis), in both adults and young, but not in tawny owls (Strix aluco). In yellow-necked mice (Apodemus flavicollis), as the main prey of tawny owls and Ural owls in the area, herpesvirus was detected in the organs of 2 out of 40 mice captured at the same locations as the owls. Phylogenetic analysis showed that the herpesvirus sequences detected in the Ural owls differed from the herpesvirus sequences detected in the yellow-necked mice. The results indicate that herpesvirus infection exists in the breeding wild Ural owl population. However, herpesvirus-infected owls did not show any clinical or productivity deviances and, based on a phylogenetic comparison of detected herpesvirus sequences and sequences obtained from Genbank database, it seems that mice and other rodents are not the source of owl infections. The most probable transmission pathway is intraspecific, especially from adults to their chicks, but the origin of herpesvirus in owls remains to be investigated.

Large-scale spatial patterns of small-mammal communities in the Mediterranean region revealed by Barn owl diet

Due to mainly opportunistic hunting behaviour of Barn owl can be its diet composition used for assessing local structure of small-mammal community. We evaluated the structure of small-mammal communities in the Mediterranean region by analysing Barn owl diet using own pellets and literature data (85 localities comprising 182,343 prey individuals). Contrary to widely accepted macroecological theory, we found a latitudinal increase of small-mammal alpha diversity, a less distinct west–east increase and lower diversity on islands. The mean prey weight decreased with increasing latitude, while on islands it decreased with increasing island area. The mean prey weight on islands was further negatively affected by mean land modification by human and positively affected by its range. The diet diversity on islands was not affected either by island area or its distance from the mainland. Its composition largely conformed to the main pattern pronounced over whole the region: an unexpected homogeneity of small-mammal community structure. Despite high beta diversity and large between-sample variation in species composition, Crocidura (+ Suncus etruscus) and murids (Apodemus, Mus, Rattus, in marginal regions partly replaced by gerbillids, Meriones or Microtus) composed more than 90% of owl prey in 92% of samples. Peak abundances of these widespread species are associated with a dynamic mosaic of dense patches of sparse herb vegetation and evergreen sclerophyllous shrublands interspersing areas of human activity, the dominant habitat of the inner Mediterranean and richest food resource for foraging Barn owls. The respective small-mammal species can be looked upon as invasive elements accompanying large scale human colonization of the region since the Neolithic and replacing original island biota. Our study documented that desertification of the Mediterranean played an important role in shaping inverse latitudinal gradient in diversity of small-mammals that contradicts to widely accepted mecroecological theory.

From owl prey to human food: taphonomy of archaeological small mammal remains from the late Holocene wetlands of arid environments in Central Western Argentina

The present study analyses small mammal bone and tooth accumulations recovered in three open-air archaeological sites from northern Mendoza (Argentina) in the central Monte Desert, one of the most arid rangelands of South America. The sites, with radiocarbon dates between ca. 2100 and 400 years BP, are located on the margins of a now-extinct swamp that formed a more widespread wetland environment in the past. In order to recognize the agents responsible for such bone and tooth accumulations, a taphonomic analysis was conducted evaluating relative abundances of skeletal elements, breakage patterns, digestive corrosion, signs of anthropic activity and post-depositional processes. The taphonomic analysis allowed the detection of owls and humans as the agents responsible for small mammal accumulations. On the one hand, the low proportion and degree of digested diagnostic elements, among other taphonomic processes, suggest owl pellet-derived small mammal assemblages. On the other hand, the thermo-altered elements detected, some showing a differential burning pattern, the abundance of large-sized and gregarious small mammals and the identification of cut-marks on a caviid femur shaft are possibly due to human exploitation/consumption of small mammals.

Predation risk in relation to brain size in alternative prey of pygmy owls varies depending on the abundance of main prey.

Large brains in prey may select for adoption of anti-predator behavior that facilitates escape. Prey species with relatively large brains have been shown to be less likely to fall prey to predators. This results in the prediction that individuals that have been captured by predators on average should have smaller brains than sympatric conspecifics. We exploited the fact that Eurasian pygmy owls Glaucidium passerinum hoard small mammals and birds in cavities and nest-boxes for over-winter survival, allowing for comparison of the phenotype of prey with that of live conspecifics. In Northern Europe, main prey of pygmy owls are voles of the genera Myodes and Microtus, while forest birds and shrews are the most important alternative prey. Large fluctuations (amplitude 100-200-fold) in vole populations induce rapid numerical responses of pygmy owls to main prey populations, which in turn results in varying predation pressure on small birds. We found, weighed and measured 153 birds in food-stores of pygmy owls and mist-netted, weighed and measured 333 live birds of 12 species in central-western Finland during two autumns with low (2017) and high (2018) pygmy owl predation risk. In two autumns, individuals with large brains were captured later compared to individuals with small brains, consistent with the hypothesis that such individuals survived for longer. Avian prey of pygmy owls had smaller heads than live birds in autumn 2018 when predation risk by pygmy owls was high. This difference in head size was not significant in 2017 when predation risk by pygmy owls was reduced. Finally, avian survivors were in better body condition than avian prey individuals. These findings are consistent with the hypothesis that pygmy owls differentially prey on birds in poor condition with small brains. These findings are consistent with the hypothesis that predation risk imposed by pygmy owls on small birds in boreal forests varies depending on the abundance of the main prey (voles).

Predation risk in relation to brain size in alternative prey of pygmy owls varies depending on the abundance of main prey

Predation risk in relation to brain size in alternative prey of pygmy owls varies depending on the abundance of main prey

Barn owls as biological control agents: potential risks to non‐target rare and endangered species

AbstractRodent agricultural pests cause significant food loss every year. Attempts at mitigation via chemical pest control may cause secondary poisoning and harm non‐target species. Biological pest control by bolstering barn owl Tyto alba populations through the provision of artificial nest boxes is in use in several countries. The national biological pest control project of Israel began in the early 1980s in the Mediterranean zone and was subsequently expanded to the northwestern Negev desert, including areas adjacent to nature reserves and natural sand dunes, a threatened habitat in Israel. We analyzed prey of barn owls in the northwestern Negev to determine whether owls preyed on non‐target endemic, threatened rodents. A total of 14 632 prey items were collected from 95 nesting boxes between 2013 and 2016. We found that barn owls feed on protected and locally endangered species such as Gerbillus andersoni allenbyi (vulnerable − VU), Gerbillus pyramidum (VU), the endemic Meriones sacramenti (endangered) and Gerbillus gerbillus (critically endangered). These species constitute a significant proportion of barn owl diets (sometimes more than half of the prey items in a single nest box), especially in areas under 5 km from sand dunes, suggesting that bolstering the barn owl population may threaten locally endangered species. It could be hypothesized that agricultural crops serve as a resource for endangered species, allowing their numbers to increase, in which case their conservation status should be reassessed. However, extensive rodent trappings in agricultural fields in the region revealed <1% Gerbillus individuals, while in nearby dunes only gerbils were trapped. Insufficient data are available to assess whether or not M. sacramenti could have become a local pest. Our study highlights the risks that may be associated with the use of barn owls as rodent control agents in areas where natural open landscapes and nature reserves are interspersed with agricultural landscapes.

Site occupancy and reproductive dynamics of California spotted owls in a mixed-ownership landscape

Biodiversity conservation in mixed-ownership landscapes often depends on contributions from privately-owned lands, where natural resource development can alter and produce novel habitat conditions for species of conservation concern. A lack of research on private lands stemming from access issues and concerns over regulatory outcomes, however, often limits evaluation of the impact of land management. The California spotted owl (Strix occidentalis occidentalis), for example, often occurs in mixed-ownership landscapes but research on this species has occurred primarily on public lands. Therefore, we conducted the first large-scale private-public cooperative and comparative analyses of California spotted owls inhabiting mixed-ownership landscapes in the Sierra Nevada, California, USA. We surveyed 151 spotted owl sites from 2013 to 2017 within two study systems: one comprised primarily of public lands (national forests) where the owl population has declined over the last ∼20 years and a set of study areas comprised mostly of private lands on which relatively high estimates of site occupancy were recently reported. Multistate occupancy modeling indicated that the probability of occupancy and successful reproduction by owls depended on site status in the previous year, with both probabilities highest at sites where owls successfully reproduced in the previous year, intermediate at occupied sites where owls had not successfully reproduced, and lowest at previously unoccupied sites. Site occupancy probability was higher at low-elevation sites and lower at sites that contained more open area and younger forest. Successful reproduction by owls was also more likely at low-elevation sites and at sites with more north-facing slope and younger forest with high basal area of hardwoods. Study areas with more private lands tended to occur at lower elevations and have greater amounts of younger forest with high basal area of hardwoods, which may have contributed to higher occupancy and reproductive probabilities than the study area with more public land. Thus, differences in occupancy and reproductive probabilities between study areas appeared to be the result of differences in topographic and vegetation conditions that likely promote populations of key spotted owl prey species. Our results suggest that private lands in mixed-ownership landscapes may contribute to spotted owl conservation by conferring different benefits to owls than public lands and, more broadly, highlight the importance of including private lands in conservation research and planning.

Effectiveness of vole control by owls in apple orchards

Abstract Biological pest control is gaining greater acceptance as an important part of integrated pest management for sustainable agriculture. However, knowledge regarding biological control of rodent pests is limited, and its effectiveness in temperate areas has not been quantified. In traditional Japanese apple orchards, the Ural owl Strix uralensis breeds in tree hollows and preys on the Japanese field vole Microtus montebelli, a native pest species that can harm fruit production. In this study, we hypothesised that the Ural owl, a generalist predator, can act as a biological control agent by reducing vole densities in temperate orchards. To quantify the pest control effects of breeding Ural owls, we first analysed the diet of individual owls nesting in apple tree hollows. Second, we installed nest boxes in orchards to attract breeding owl pairs and collected data on vole population changes around owl nests to compare with control areas. The population changes were analysed using a generalised linear mixed model to assess the effect of breeding owls within their breeding territory. The model considered seasonal fluctuations in vole population size as well as surrounding land‐use. We also examined vole populations around the owl nests in April, and the distance between nests and forested areas, to determine if these variables influenced nest site selection. Voles were the primary prey of Ural owls breeding in orchards and the owls reduced vole populations within their estimated breeding territories by 63% (±SE: 53%–70%) compared with the predicted density without owls. Owls preferred to nest in orchards with higher vole population densities in April. Our findings also indicate that higher occupancy rates are possible by distributing nest boxes based on Ural owl breeding territory size (306 m radius circle in our study). Synthesis and applications. As breeding Ural owls provide significant pest control effects within their breeding territories, the reintroduction of breeding Ural owl pairs within orchards would contribute to rodent pest control. Promoting the reproduction of native raptors in agricultural areas can be an option for developing integrated pest management while simultaneously maintaining regional biodiversity.

Spatial and temporal patterns in the diet of barn owl (Tyto alba) in Cyprus

BackgroundThe barn owl, a nocturnal raptor with cosmopolitan distribution, shows a great adaptability to different environments. Regarding prey, the barn owl is a rather selective species, but if changes in the abundance of the selected prey occur, it becomes an opportunistic predator and easily incorporates other prey in its diet, using a wide range of prey species and foraging habitats. Small rodents are usually the prey mostly used. Compared to the populations of north and eastern Europe, barn owl populations in the Mediterranean area have been the least studied. In Cyprus, where barn owl is a common bird species, there are no studies on its diet and feeding ecology. This study was carried out to contribute to the spatial and temporal patterns barn owl diet in Cyprus also providing information on small mammals’ presence and species composition on the island.MethodsThis study was based on 1407 regurgitated pellet analysis that were collected from 26 sites representing six major habitat types on central and southern Cyprus from summer 2013 to summer 2014. The diet of the barn owl was described in terms of seasonal average biomass and numerical percentages of each prey species and compared by Kruskal–Wallis test. Seasonal prey diversity and evenness indices were also calculated. Principal component analysis (PCA) was performed on the prey biomass proportion data assigned to six major habitat types with regard to elevation, vegetation and human uses.ResultsLow prey diversity was found comprised mainly of rodents (overall means 96.2 and 95.7% by number and biomass, respectively). Mice followed by rats were most important prey whereas insectivores, birds and insects were minor components of the owl’s diet. Evenness and diversity values were relatively similar among seasons. PCA differentiated mainly between lowland areas where mice were more abundant prey and mountainous areas where rats dominated in the diet. Insectivores correlated with birds, prey types characterizing several lowland and highland habitats.ConclusionsThe barn owl prey composition in Cyprus suggests an opportunistic foraging behavior, low prey species diversity with variations in the main rodent prey that could be explained by their distribution, seasonal activity and habitat preferences.

Insights Into the Natural History of the Little Known Maned Rat Lophiomys imhausi through Examination of Owl Pellets and Prey Remains

Maned rat Lophiomys imhausi is a highly unusual, but very little known rodent that is endemic to East Africa. A population from the highlands of central Kenya was studied through analysis of owl pellets and prey remains, including one incidental observation. Over 28 months, 40 individual rats were documented, of which two were juveniles. The mean length of time between discovery of rat remains in any one owl territory was once every 5.3 months, and the maximum number of rats found in any single owl territory over one year was five. Maned rat density was low and was estimated at 1 rat/km2. Their lower altitudinal limit in Kenya is c. 1900 m, and eagle owls and humans are important predators. Maned rats are not uncommon in highly altered habitats and they may require poisonous plants in addition to Acokanthera spp. for anti-predator defense.

Weather-Dependent Variation in the Winter Diet of Urban Roosting Long-Eared Owls Asio Otus in Pécs (Hungary)

Long-eared Owls (Asio otus) usually winter in groups in settlements, hunt at night and rest in evergreen trees during the day. From prey remnants regurgitated as pellets, one can detect species present in their hunting areas and changes in their abundance. Our aim was to reveal how the ratio of small mammal species in Long-eared Owl prey changes during the winter, since weather can influence hunting success and the availability of prey. There were 40–60 Long-eared Owls wintering in the city of Pécs. From November 2014 to mid-March 2015 we collected 6,328 pellets from which 9,087 prey remains were identified. 97.5% of prey consisted of small mammals belonging to 21 species. The diversity of small mammals in the pellets collected in November was significantly lower in comparison with other months. With the increase of precipitation, the relative abundance of the Common Vole (Microtus arvalis) and Common Dormouse (Muscardinus avellanarius) decreased, while that of the Striped Field Mouse (Apodemus agrarius) and Wood Mouse (A. sylvaticus) increased. In the periods when the area was covered by snow, the ratio of the Common Vole as prey continually decreased, probably because it stayed under the snow. Since the availability of the Common Vole declined, the proportions of the Striped Field Mouse and Lesser White-toothed Shrew (Crocidura suaveolens) as alternative prey grew significantly. In low temperature periods, Brown Rats (Rattus norvegicus) and birds are more often preyed upon. Despite the hunting area being predominantly urban, species preferring open grassland habitats were significantly more common. As winter progressed, the role of forest-dwelling species in the diet continuously increased.

Weavers as prey of Barn Owls.

Barn Owls Tyto alba are widespread globally, and feed largely on rodents, but also birds. In Africa, weavers are an important component of avian prey. 44 studies were found that list weavers as prey of Barn Owls, with 11 species of Ploceidae weavers identified to species level, although there are likely many other weaver species that have been taken but not yet identified. Hunting strategies of the Barn Owl are taking weavers at their nests at night (four records), or taking roosting weavers from reedbeds. Barn Owls have been recorded at Red-billed Quelea Quelea quelea colonies, where they presumably pick up recently fledged juveniles.

Insights Into the Natural History of the Little Known Maned Rat Lophiomys imhausi through Examination of Owl Pellets and Prey Remains

Insights Into the Natural History of the Little Known Maned Rat <i>Lophiomys imhausi</i> through Examination of Owl Pellets and Prey Remains

The effect of elevation and habitat cover on nest box occupancy and diet composition of Boreal Owls Aegolius funereus

ABSTRACTCapsule: Diet composition of Boreal Owls Aegolius funereus was not affected by habitat cover, but it changed along the elevational gradient.Aims: To assess the effect of elevation and habitat cover on nest box occupancy and diet composition of a central European population of Boreal Owls.Methods: A Boreal Owl population was studied in the Šumava Mountains, Czech Republic, at elevations from 500 to 1300 m above sea level (asl), during 1984–2005.Results: Boreal Owls occupied more frequently nest boxes above 600 m asl, but they did not clearly prefer any elevational band. Habitat cover did not affect the number of nesting attempts. There was also no relationship between habitat cover and diet composition. However, diet composition significantly changed along the elevational gradient. In particular, the proportion of alternative prey of Boreal Owls, i.e. birds and shrews Sorex sp., rose with increasing elevation. The proportion of voles Myodes and mice Apodemus in the diet decreased with increasing elevation. Among bird prey, the proportion of finches Fringillidae positively correlated with elevation.Conclusions: Central European Boreal Owls did not show a clear preference for any habitat cover or elevational band, but the quality of the owls’ diet significantly decreased with increasing elevation.

Recent and subrecent diet of the barn owl (Tyto alba) in Slovakia

Abstract We completed data on the diet of the barn owl (Tyto alba) predominately from pellets for the period of the last 50 years from Slovakia. We analyzed material from 251 locations and 16 territorial units. The aggregate represents 119,231 pieces of prey from 47 species of mammals (Mammalia, 95.7%) and 58 species of birds (Aves, 3.9%), with a small representation of amphibians, reptiles (Amphibia and Reptilia, 0.2%) and invertebrates (Invertebrata, 0.2%). The obtaining of food among the owls is limited to synanthropic environments and the surrounding agricultural landscape, and the centre of its distribution in the recent period (i.e. the past 50 years: 1965-201 5) has been concentrated mainly on the southern parts of Slovakia. In this environment the common vole (Microtus arvalis, 59.6%) is the primary prey. Additional prey are rodents of the family Muridae: Mus musculus (5.6%), Micromys minutus (2.2%), Apodemus microps (2.2%), A. flavicollis (2.0%), A. sylvaticus (1 .6%) and A. agrarius (1 .5%); insectivores of the family Soricidae: Sorex araneus (6.2%), S. minutus (2.4%), Crocidura leucodon (4.8%) and C. suaveolens (2.8%); and the house sparrow Passer domesticus (2.9%). In the higher situated Turcianska kotlina Basin the species M. arvalis (74.3%) has higher domination, and instead of the white-toothed shrews the water shrews Neomys anomalus (2.8%) and N. fodiens (1 .3%) are more abundantly represented. In 3 localities owls focused on hunting bats; for example, in the church in Ratková the order Chiroptera made up 35.2% of prey. From the subrecent period (i.e. from before more than 50 years ago) we evaluate 4 samples from the territory of Slovakia with 15,601 pieces of prey ofT. alba. Before more than 50 years ago owls were also more abundantly represented at higher elevations in Slovakia, evidence of which is Weisz’s collection of pellets from 1 6 localities in the Ondavská vrchovina Upland in the years 1945 to 1963, but also a registry of data from the 19th and 20th centuries from higher located basins. In 4 samples of food from the subrecent period diversity in the representation of owl prey is higher, accompanied by low domination ofM. arvalis and a more abundant representation of murids from the genera Mus and Apodemus. The oldest sample, dated to the 16th century, is from a church in Žilina-Rudiny