Strix Aluco Research Articles

The long-term pattern of change in Tawny Owl female characteristics in a local population indicates a rapid shift in body size, but not in body mass

The long-term pattern of change in Tawny Owl female characteristics in a local population indicates a rapid shift in body size, but not in body mass

Space use during the breeding season of three different forest-dwelling owl species in an area of sympatry: a case study of male hunting home-range sizes and overlaps

Abstract Heterospecific interactions amongst sympatric animals can significantly influence their spatiotemporal behaviours. In birds of prey, ecological relationships such as predation risk or competition for space and/or food may induce mutual spatial avoidance, affecting home ranges’ distribution and sizes. However, studies simultaneously monitoring multiple sympatric owls or diurnal raptors are exceptional. Therefore, we studied four sympatric owls to obtain findings on spatial arrangements of nocturnal/hunting home ranges during the breeding season. Individual males from three of the four studied species (Eurasian Pygmy Owl [Glaucidium passerinum], Boreal Owl [Aegolius funereus], and Tawny Owl [Strix aluco]) were radio-tracked in an area co-inhabited by an apex intraguild predator, Eurasian Eagle-Owl (Bubo bubo). The findings revealed a 78% overlap in the hunting ranges of Boreal and Eurasian Pygmy Owls; in contrast, their ranges overlapped only by 25% and 15%, respectively, with that of the Tawny Owl. Further, the Eurasian Eagle-Owl nest site was located within the hunting ranges of both smaller owl males, unlike the Tawny Owl’s home range, which maintained a respectful distance. The Boreal and Eurasian Pygmy Owl males avoided hunting in the Tawny Owl’s home range. In contrast, Tawny Owl male avoided Eurasian Eagle-Owls’ territory, indicating that the subordinate owl species can use the presence of an apex predator to protect themselves from medium-intraguild enemies. Although tentative due to the small sample size, this study offered unique insights into the spatial behaviours of multiple sympatric species. We encourage researchers to implement similar studies, which may provide essential information for conserving threatened species in a rapidly changing environment.

Lifetime Fitness Variation Across the Geographical Range in a Colour Polymorphic Species.

The maintenance of variation (i.e., different phenotypes) for heritable traits that are under selection, despite expectations of selection eroding variation and favouring only the fittest phenotype, represents an evolutionary paradox. Here, we studied variation in life-history traits in five populations of colour polymorphic tawny owls (Strix aluco) across Europe that have been individually studied for 13 years. Tawny owls show heritable plumage colour variation ranging from less pigmented (grey) to more heavily pigmented (brown-red). The breeding life span (BLS), lifetime egg production (LEP), lifetime reproductive success (LRS) and the number of years skipped between breeding attempts (NYS) varied between the study populations, with LEP and LRS varying across colour morphs in a population-specific fashion. Thus, grey tawny owl females have higher lifetime fledgling and egg production than brown-red females in some populations, but vice versa in others. Hence, our findings demonstrate disruptive selection of tawny owl plumage colourations across their European range, which may be one factor maintaining variation in heritable tawny owl colourations.

The Ural Owl as a Keystone Species in Interspecific Interactions Among Avian Predators—A Review

Ural owls are one of the largest owls in Europe, exhibiting known aggressive behaviour toward other raptors. They are known to interact with nearly all sympatric owls and many diurnal raptors. To summarise these interactions, a literature search was undertaken in the Web of Sciences and Scopus databases using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses methodology as well principal books on owl biology. The search revealed 22 relevant publications that (along with the book data) described the Ural owl’s relations with seven owls and six diurnal raptor species. The Ural owl is subordinate only to the largest predators like golden eagles and eagles, although only its chicks are known to be killed. Contrary to that, the Ural owls shape the distribution of numerous other species, mostly by strong competition (e.g., forcing tawny owls to breed in suboptimal habitats) or by predation (killing smaller owls and diurnal raptors). Their occurrence could be also protective for some species like boreal owls thanks to the removal of intermediate predators. The relations of Ural owls with goshawks are interesting, which seem to live in some balance—temporal avoidance of activity with frequent co-occurrence. Thanks to their association with old-growth forests and their impact on other predators in their territories, Ural owls act as keystone species in mountainous and boreal forests in Europe. Considering this ecosystem service, Ural owls should be effectively protected e.g., by designing forest-management-free zones around their nesting sites.

Monitoring of toxic metals(loids) in fifteen raptor bird species of Iran.

The current study was conducted to identify the contamination of 10 toxic metals(loids) (mercury (Hg), lead (Pb), cadmium (Cd), chromium (Cr), zinc (Zn), copper (Cu), selenium (Se), nickel (Ni), arsenic (As) and aluminium (Al)) in the feathers of 15 raptor bird species, which tries to analyze the adverse effects, taxonomic affiliation, spatial distribution, habitat type, and effect of age. During 2020-2022, 476 feathers of 115 birds were collected and the primary feathers of each bird were sampled and an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to analyze the toxic metals(loids). It was found that there is a statistically significant difference between the concentration of metals(loids) and the studied birds (except for As) (p < 0.05). The highest average concentrations of Hg and Al in tawny owl (2.26 and 1184.75 mg/kg dry weight, respectively), Cu in spotted little owl (10.45 mg/kg), and Pb, Cd, Cr, Zn, Se, Ni, and As in pallid scops owl (5.44, 0.19, 3.93, 251.99, 4.84, 5.45, and 0.52 mg/kg, respectively) were observed. According to the threshold level of elements, the status of Pb, Cr, Ni, and Al can be reported as unfavorable. In the current project, there was a statistically significant difference between the concentration of Hg, Cr, and Ni in the studied birds and spatial distribution (p < 0.05). The pollution of birds in Khuzestan province with toxic elements was considerable and in all ten elements investigated, this province is among the first 5 provinces in terms of pollution. In the case of most of the investigated elements, namely Pb, Cd, Cr, Zn, As, and Ni, the highest concentration was related to the habitat of open grasslands (2.10, 0.04, 0.98, 64.66, 0.15, and 1.26 mg/kg, respectively). Regarding most of the studied elements, adult birds had the highest concentration, but elements such as Ni and As showed a reverse trend so that nestling birds had higher concentrations of Ni and As in their feathers. As a conclusion, tawny owl, spotted little owl, and pallid scops owl can be introduced among the important group of raptor birds as distinct indicators of environmental pollution.

Spatial Ecology of a Resident Avian Predator During the Non-Breeding Period in Managed Habitats of Southeastern Europe.

Describing home range and resource selection is crucial for understanding ecological needs and creating conservation programs. Still, our knowledge of spatial and behavioural ecology for most species remains limited. Here, we used satellite transmitters to investigate core and home range sizes, habitat selection, and roost characteristics in seven tawny owl males in Western Serbia during the autumn-winter period 2023. Using minimum convex polygon (MCP) and autocorrelated kernel density estimation (AKDE), we found clear variability in core area and home range sizes. Also, adult and heavier males have smaller core area and home ranges than juvenile and lightweight individuals. The Bhattacharyya coefficient showed minor home range overlap in tagged males. The final model for evaluation of habitat selection suggests that the likelihood of owl occurrence was positively correlated with the share of anthropogenic infrastructure and negatively associated with the increase in the proportion of cultivated land within the home range. However, scores of model performance metrics showed moderate predictive accuracy, implying that other unmeasured variables may dictate species presence. Our study illustrates the ecological plasticity and ability of the tawny owl to adapt to a human-modified environment while providing new information about the spatial ecology of this widespread predator in Europe.

Variation and Acoustic Stability in the Call Duration of Tawny Owl Strix aluco Males

Variation and Acoustic Stability in the Call Duration of Tawny Owl Strix aluco Males

The Multi-Functional Use of Large Tree Cavities by Arboreal Vertebrates in a Temperate Broadleaved Forest of Eastern Europe.

Tree cavities offer protected shelters and resources for arboreal vertebrates worldwide. In general, cavities with larger openings are better accessible for predators and are avoided by smaller species for breeding, but can still be attractive for occasional use. The current study explores the diversity of functional use types and species interactions at the largest available tree cavities (entrance width ≥ 10 cm) in a temperate European forest with a low number of large cavity-breeding species. Year-round camera observations at 9 cavities (range 0.7-3.5 years) revealed 34 visiting species of birds and mammals, including non-cavity-breeding species. The top predator threatening other large-cavity users was European pine marten (Martes martes), which regularly visited each cavity year-round, on average every 0.7 months. Tawny owl (Strix aluco) was the only species successfully breeding in cavities, arguably because of its ability to defend the nests. However, other species visited cavities at an average rate of 1.5 visits per day, making predominantly short visits (less than 30 s) interpreted as exploration, searching for food, or inspecting for the presence of owls (mobbing). Making short visits and time segregation with predators was a behavioural strategy to exploit cavities for most species. These results confirm that, similarly to other keystone structures (large arboreal nests, ground burrows, etc.), large tree cavities attract a significant part of the arboreal vertebrate community and enrich their habitats. To sustain these functions in wooded ecosystems, management should provide a surplus of available cavities and diversity of their characteristics even when the apparent number of breeding species is low.

Antipredator responses of bats during short boreal nights with variable climatic conditions.

The threat of predation can influence the behavior of animals. To minimize the impact of predation, animals rely on antipredatory responses and effectively balance these responses with other activities to maximize survival. Boreal bats are nocturnal animals that must forage within a narrow time frame during short, light summer nights with unpredictable weather. Despite having no specialized predators, boreal bats are still subject to predation. However, whether they express antipredatory responses has not been established. We studied antipredatory responses and responses to climatic conditions in boreal bats in 2 settings: 1) during roost emergence; and 2) during foraging within Tawny Owl territories and at locations with no Tawny Owl sightings. Acoustic data were collected at 23 roosts and 10 foraging grounds. Two controlled predation threats were used-playbacks of Tawny Owl calls and fledgling calls. Fledgling calls were only played during roost emergence. In both experiments, music and no treatment were used as controls. We also incorporated weather variables in the model. According to our results, bats tend to delay their emergence by 16 min when Tawny Owl calls were played outside the roost, but this effect was not noticeable when weather variables were included. There was no difference in exit time when music or fledgling sounds were played. While foraging, bats reduced their activity in Tawny Owl territories when calls of owls or music were played compared to no treatment. These results suggest that bats might display variable antipredatory responses, but weather influences behavior of bats more than predation risk, highlighting the importance of energy-saving strategies at northerly latitudes.

Sex allocation is color morph-specific and associated with fledging condition in a wild bird.

Melanin-based color polymorphism is predicted to evolve and maintain through differential fitness of morphs in different environments, and several empirical studies indicate that life history strategies, physiology, and behavior vary among color morphs. Sex allocation theory predicts that parents should adjust their sex allocation based on differential costs of raising sons and daughters, and therefore, color morphs are expected to modify their brood sex ratio decisions. In color polymorphic tawny owls (Strix aluco), the pheomelanistic brown morph is associated with higher energy requirements, faster growth, and higher parental effort than the gray morph. As hypothesized, we find that brown tawny owl mothers produced more daughters in early broods and more males in late broods, whereas gray mothers did the opposite. At fledging, daughters of early broods and of brown mothers were heavier than those of late broods or gray mothers. Hence, larger and more costly daughters appeared to benefit more than males from being born to brown mothers early in the season. Brown mothers breeding later in the season produced more cheap sons, while gray mothers face fewer challenges under limited resources and favor daughters. These findings suggest that environmental conditions influence brood sex allocation strategies of genetically determined color morphs differently.

Tawny Owls Strix aluco from a southern European population differ in size and degree of reverse sexual dimorphism from northern European counterparts

ABSTRACT Tawny Owls in southern Europe were trapped and measured. Compared to males, the females were larger, heavier, and more greyish in colour, but there was a large biometric overlap. The variable with the highest Storer’s dimorphism index (SDI) was weight, though our population had one of the smallest dimorphisms observed in Europe for weight. It has been proposed that differences in diet could lead to differing behaviour and, in consequence, the observed dimorphism degree (SDI) by natural selection.

Trophic niche segregation in a guild of top predators within the Mediterranean Basin.

Niche theory predicts that closely related and ecologically similar species with overlapping distribution ranges can coexist through resource partitioning that limits interspecific competition. However, studies examining the mechanisms promoting coexistence of top predators at a large geographical scale are still scant. Here, we describe the foraging ecology of 3 sympatric owl species (Northern long-eared owl [Asio otus], Tawny owl [Strix aluco], Eurasian eagle owl [Bubo bubo]) in the Mediterranean Basin. We review 160 studies reporting diet information (212,236 vertebrate preys) and investigate among-species differences in diet metrics (diversity, evenness, prey size, and proportion of mammals) and their variation along geographical and environmental gradients. Moreover, we test whether diet metrics differ in presence or absence of the other predators. All the 3 species mainly rely on small mammals, but they significantly differ in diet metrics. The smallest predator (i.e., long-eared owl) shows a higher level of specialism on small mammals (highest proportion but lowest diversity of mammals in the diet) compared to the larger ones. In addition, mean prey size significantly increases with predator body size (long-eared owl < tawny owl < eagle owl). Finally, interspecific competition results in an increase of diet diversity and evenness in the long-eared owl, and species' diet also varies in response to environmental factors. The 3 species thus segregate along several dietary niche axes over a large spatial scale and according to both morphological characteristics (i.e., body size) and environmental variables. Such dietary niche segregation may adaptively buffer interspecific competition costs, ultimately allowing coexistence.

Genomic basis of melanin-associated phenotypes suggests colour-specific environmental adaptations in tawny owls.

Feathers comprise a series of evolutionary innovations but also harbour colour, a key biological trait known to co-vary with life history or complex traits. Those relationships are particularly true in melanin-based pigmentation species due to known pleiotropic effects of the melanocortin pathway - originating from melanin-associated phenotypes. Here, we explore the molecular basis of melanin colouration and expected co-variation at the molecular level in the melanin-based, colour polymorphic system of the tawny owl (Strix aluco). An extensive body of literature has revealed that grey and brown tawny owl colour morphs differ in a series of life history and behavioural traits. Thus, it is plausible to expect co-variation also at molecular level between colour morphs. To investigate this possibility, we assembled the first draft genome of the species against which we mapped ddRADseq reads from 220 grey and 150 brown morphs - representing 10 years of pedigree data from a population in Southern Finland - and explored genome-wide associations with colour phenotype. Our results revealed putative molecular signatures of cold adaptation strongly associated with the grey phenotype, namely, a non-synonymous substitution in MCHR1, plus 2 substitutions in non-coding regions of FTCD and FAM135A whose genotype combinations obtained a predictive power of up to 100% (predicting grey colour). These suggest a molecular basis of cold environment adaptations predicted to be grey-morph specific. Our results potentially reveal part of the molecular machinery of melanin-associated phenotypes and provide novel insights towards understanding the functional genomics of colour polymorphism in melanin-based pigmented species.

Vocal interaction between Tawny Owl (Strix aluco) and Ural Owl (Strix uralensis) in the Middle Volga

The work studied the co-vocalization of Tawny Owl and Ural Owl. Researched primarily using digital voice recorders. Co-vocalization was revealed only in spring. This is due to the breeding season of birds. The roll call of two species of owls was recorded 2 h 30 min after sunset. Co-vocalization was always observed from 21:00 to 22:00 hours. Duration of co-vocalization of the Tawny Owl and the Ural Owl ranged from several sec to 6 min. During periods of co-vocalization, the Tawny Owl managed to produce twice as many calls as the Ural Owl. The Tawny Owl was the first to start calling, and later the calls of the Ural Owl joined it. The Tawny Owl stopped vocalizing, and the Ural Owl continued to call after it. The calls of each of the two owl species in shared habitats were recorded primarily at different times. More often, the Tawny Owl began vocalization 30 min after the Ural Owl stopped calling. The natural and climatic conditions of the area in which co-vocalization was noted were studied. Co-vocalizations were observed in the temperature range from +3 to +7°C. Joint calls were recorded at wind strength from 4 to 7 m/s, at cloud cover from 40 to 90%, at pressure from 734 to 744 mm Hg.

Small mammals of the Góra Świętej Anny Landscape Park (south-western Poland) in the diet of two owl species.

The knowledge about small mammals of the Góra Świętej Anny Landscape Park is lacking. Here I provide data about diversity of small mammals identified from the pellets of the two owl species: the tawny owl Strix aluco and the barn owl Tyto alba. Pellets derived from 1999–2024. The material was collected at two breeding sites of the barn owl and at 5 sites of regular occurrence of tawny owl. In total, 1549 prey items have been identified: 1433 prey consumed by the barn owl, and 116 prey consumed by the tawny owl. 18 mammal species were identified: 5 species of Soricomorpha, 1 Chiroptera and 12 Rodentia. Rodents were the most important prey group for both owl species. Depending on owl species, the most numerous prey species were Microtus arvalis and Mus musculus for the barn owl, and Apodemus flavicollis together with Clethrionomys glareolus for the tawny owl. The results are the first detail data about diversity of small mammals in the the Góra Świętej Anny Landscape Park and one of the few in whole Opole Voivodeship.

The food of the tawny owl Strix aluco in the Oder Valley in the Opole Voivodeship (south-western Poland).

The aim of this paper was to describe the diet of the tawny owl Strix aluco in the Oder Valley in the Opole Voivodeship, south-western Poland. Tawny owl pellets were collected in the years 1996-2024 from 22 sites, grouped into five distinct localities. In total 19 species of mammals were found: 4 species of Soricomorpha, 1 Chiroptera, 1 Lagomorpha, 12 Rodentia and 1 Carnivora. Among 1103 identified prey items (902 belonged to mammals), 77.1% belonged to Rodents, which played the most important role as a prey at every locality. Microtus arvalis, Apodemus agrarius, A. flavicollis and Clethrionomys glareolus were the most important prey species in the tawny owl`s diet. Crocidura suaveolens, M. arvalis, Mus musculus and A. agrarius were more frequently caught by tawny owl in farmlands, whereas A. flavicollis and C. glareolus were more abundant in forest habitats. High domination of Arvcollidae with Muridae in the diet, together with very low share of soricomorphs and other group of mammals, may indicate a considerable degradation of once natural environment of the Oder Valley within this section, currently dominated with farmland monocultures.

Distribution of the Quill Mite Bubophilus aluconis Parasitising Western Palaearctic Owls Belonging to the Genus Strix.

Background: The paper presents the results of studies on the distribution of the parasitic quill mite species Bubophilus aluconis (Acariformes: Syringophilidae) in the feather quills of the Western Palaearctic owls of the genus Strix, that is, tawny owl S. aluco, collected in Poland and Sweden, the Ural owl S. uralensis, from Poland, Sweden, and Finland, and the great grey owl S. nebulosa, from Sweden and Finland. The two latter species are new hosts for B. aluconis. Methods: Feather samples of the tawny owl, Ural owl, and great grey owl used in this study come from Prof. Marian Cieślak's private collection, which contains feathers of Western Palearctic birds of prey and owls. Each of the 77 tawny owl, 75 Ural owl, and 55 great grey owl specimens are represented either by whole dry wings or a full complement of flight feathers (primaries (P) and secondaries (S)) and tails (rectrices (R)). Particular types of feathers were coded as follows: Ps, Ss, R, primary greater upperwing coverts (PGUppC), secondary greater upperwing coverts (SGUppC), primary greater underwing coverts (PGUndrC), secondary greater underwing coverts (SGUndrC), uppertail coverts (UppTC), and undertail coverts (UndrTC). Results: The prevalence was relatively low for all of the examined birds, that is, 12% for S. uralensis (N = 79), 2.6% for S. aluco (N = 77), and 3.6% for S. nebulosa (N = 55). In total, we examined 37,260 flight feathers and coverts. The mite B. aluconis occupied only the inner S of the tawny owl, secondary greater under and upperwing coverts of the great grey owl, and inner Ss, primary and secondary upperwing coverts, UndrTC, and coverts from the scapulars of the Ural owl. Conclusion: We hypothesise that the absence of these parasites in the examined P, S, and R suggests that these feather types might be unsuitable for the mites due to their thick quill walls, preventing successful feeding.

РЕЗУЛЬТАТИ ОБЛІКІВ СОВ (STRIGIFORMES, STRIGIDAE) У НАЦІОНАЛЬНОМУ ПРИРОДНОМУ ПАРКУ ''ПИРЯТИНСЬКИЙ'' ТА НА ПРИЛЕГЛІЙ ТЕРИТОРІЇ

Background. The paper examines the distribution, number, voice activity of three species of owls from the Strigidae family typical for the National Nature Park "Pyriatynskyi": Tawny Owl (Strix aluco), Long-eared Owl (Asio otus) and Little Owl (Athene noctua) according to the results annual accounts for an eight-year period. Methods. The research was carried out according to the methodology, which included listening to the unprovoked vocalization of owls, and in its absence, the use of vocal provocation of birds in the evening twilight/darkness, followed by the registration of vocal signals or visual observation and counting of absolute numbers. Accounting was carried out in 35 localities during 2017-2024 at the beginning of the nesting period of owls. Results. The most numerous species in the park is the Tawny Owl, the share of individuals among other species was on average 74,9%, the total number is at least 51-53 pairs. Less numerous is the Little Owl, the share is 16%, the number is 19 pairs. The smallest number was recorded for the Long-eared Owl (7,3%), but the number is estimated at 20 pairs; this species is not registered annually. The average effectiveness of the records at the observation points is 67,2% of the places where owls were detected against 32,8% of the points without birds. Most often, owls responded to vocal provocations – 69,9% of cases of meetings with birds. Independent vocalization was noted in 25,6% of encounters. Conclusions. Bird activity is highly dependent on weather conditions: owls were most active in years when the weather was relatively warm and without significant precipitation and wind. In frosty and snowy periods of winter, some owl individuals may die from exhaustion. It was effective to involve volunteers in accounting work.

Rozšíření myšivky horské (Sicista betulina) v Pošumaví na základě rozboru potravy sov (Rodentia: Zapodidae)

Distribution of Sicista betulina in the Šumava Mts. (Bohemian Forest, SW Bohemia, Czech Republic) based on owl diet analysis (Rodentia: Zapodidae). The Šumava Mountains are one of the three areas of a relict occurrence of the northern birch mouse (Sicista betulina) in the Czech Republic. The present study summarises all records of this species obtained there by the analysis of diet of three species of owls, the Tengmalm’s owl (Aegolius funereus), to a lesser extent of the Ural owl (Strix uralensis) and tawny owl (Strix aluco). A total of 355 sample sets from 228 localities was processed, positive findings concern 57 localities where the northern birch mouse was found (322 individuals). The presence of the species was confirmed in an area of approximately 1,400 km2, which corresponds to 13 mapping fields of the KFME, four of which extend into the territories of Germany and Austria (field numbers 7047, 7148, 7249, 7350). More than a third of the localities (37.0%) and nearly two thirds of the individuals (62.4%) come from four mapping fields (7048, 7049, 7148, 7149) covering mainly a peaty alluvial plain of the upper stream of the Vltava river and its surroundings. Data obtained by observation or capturing of the northern birch mouse give a similar picture. Thus, this territory with the high proportion of relict vegetation can be considered as the core area of the current occurrence of the mouse in the Šumava Mts. The altitude range of the northern birch mouse records from owl pellets is 680–1160 m a. s. l. with a mean of 871.7 m a. s. l. Almost a third of the localities (32.0%) lie in the altitudinal range of 700–800 m a. s. l., and more than four fifths of the records (82.7%) fall within the range of 700–1000 m a. s. l. However, these are only indicative values that can be influenced by the size of the individual hunting territories of owls (especially in a landscape with a steep mountainous relief). Our results confirm the previously described zoogeographical profile of the northern birch mouse in the Šumava Mts., i.e., that its distribution is limited only to the south-eastern half of this mountain range and ends roughly in the Kvildské pláně region in the north-west. Records of the northern birch mouse on the Bavarian side of the mountain range are in full agreement with this. It can be assumed that the species occurrence in the whole Bohemian Forest is primarily shaped by its Holocene history. Furthermore, it has been confirmed that the analysis of the diet composition of the Tengmalm’s owl is an effective method of study of the geographical distribution of the northern birch mouse.

Small mammals in the diet of the barn owl Tyto alba and the tawny owl Strix aluco in localities in north-western Poland.

Analysis of food composition of two owl species (Tyto alba and Strix aluco) in 14 study sites in the years 1998–2024 revealed the presence of 22 species of small mammals. Five species of Soricomorpha (Talpa europaea, Sorex araneus, S. minutus, Neomys fodiens and Crocidura suaveolens), four species of Chiroptera (Myotis myotis, M. nattereri, Eptesicus serotinus and Nyctalus noctula), 12 species of Rodentia (Clethrionomys glareolus, Arvicola amphibius, Microtus arvalis, M. subterraneus, M. agrestis, M. oeconomus, Mus musculus, Rattus norvegicus, Apodemus agrarius, A. sylvaticus, A. flavicollis and Micromys minutus) and one species (Mustela nivalis) of the order Carnivora were found. Three species: S. araneus, M. arvalis and M. musculus clearly dominated in the diet of the T. alba. Forest rodents: C. glareolus, A. flavicollis and in one site M. arvalis were most common in the diet of S. aluco. Noteworthy is the great share of M. agrestis in the diet of S. aluco, which is rarely noted in other regions of the country. Distinctly increased share of Chiroptera (3 species) constituting 10.1% of prey items of T. alba was recorded in one site in Przelewice.