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We investigated the composition of small mammals at nine locations in the southwestern suburban zone of Warsaw (central Poland) through the analysis of the pellets of the Tawny owl Strix aluco. In total, we recorded 611 individuals of 15 species of small mammal communities in the diet. Rodents constituted the most numerous mammalian order. Among the most abundant prey we recorded were Myodes glareolus (63 individuals = 10.3% of all mammals), Apodemus agrarius (56 individuals = 9.2%) (173), Apodemus flavicollis (54 individuals = 8.8%), Mus musculus (48 individuals = 7.9%) and Microtus arvalis (44 individuals = 7.2%). We recorded also some species rarely captured by the tawny owl: Nyctalus noctula and Mustela nivalis. Species composition of small mammals of the study area resembled city parks, with several species typical for anthropogenic landscape.

Studies on the contribution of the yellow-necked mouse Apodemus flavicollis and of other vertebrates to the diet of the tawny owl Strix aluco were carried out in Warsaw (central Poland) in the years 1983–2018. The frequency of the yellow-necked mouse in owl pellets increased at the break of the 20th and 21st centuries, particularly in some woodlands in the peri-urban area of the agglomeration. In the second half of the first decade of the twenty-first century, this mouse species colonised a park in the city centre. The yellow-necked mouse may become an important competitor for the synurbic population of the striped field mouse Apodemus agrarius.

Tawny Owls Strix aluco used a wide variety of tree holes for roosting, but only a minority were used for nesting, which comprised those holes at greater heights in larger trees and with a flat base...

This study investigated the home range and habitat characteristics in tawny owls (Strix aluco), a grade II endangered wildlife species from South Korea. We tracked a breeding pair in Gyeongbuk during their brooding period using an attached radio transmitter through a satellite tracking system (WT-300: GPS-Mobile phone based Telemetry). The subjects had consecutively reproduced in a same nest for two years (2016–2017). The female's location data (six coordinates) were collected in 2016, whereas the male's (12 coordinates) were collected in 2017. Kernel density estimates were used to determine the pair's core habitats; the male had a greater movement range (2,133,971 m2) at 95% kernel density estimate than the female (19,572 m2). The male's core habitat was mostly mixed forest (50.6%), followed by coniferous forest (13.4%), nonirrigated land (10.9%), natural grassland (10.1%), and inland bodies of water (8.2%). The female's core habitat was dominated by mixed forest (36.8%), followed by non-natural barren land (21.7%), nonirrigated land (14.4%), residential areas (10%), and transportation areas (7.9%). This study is the first to track a breeding tawny owl pair on the Korean peninsula through direct satellite. Our results provide fundamental data as a case study regarding home range behavior of an owl breeding pair for developing conservation and management plan.

Strong numerical and functional responses of owls to voles in cyclic environments are well known. However, there is insufficient knowledge from the boreonemoral region in particular, with depleted populations of small mammals. In this study, we describe the dynamics of the small mammal population in Latvia from 1991 to 2016 and link them to owl population characteristics. We used food niche breadth, number of fledglings, and population trends to lay out the numerical response of six owl species to dampened small mammal population cycles. We found temporarily increasing food niche breadth in tawny and Ural owls. There were no other responses in the tawny owl, whereas the breeding performance of three forest specialist species—pygmy, Tengmalm’s, and Ural owls—corresponded to the vole crash years in Fennoscandia. Moreover, the populations of forest specialist owls decreased, and the change in the Ural owl population can be attributed to the depletion of small mammal populations. We found evidence of a carry-over effect in the eagle owl arising from a strong correlation of declining breeding performance with the small mammal abundance indices in the previous autumn. We conclude that dampening of the small mammal population cycles is an important covariate of the likely effects of habitat destruction that needs to be investigated further, with stronger responses in more specialized (to prey or habitat) species.

Most diurnal birds have cone-dominated retinae and tetrachromatic colour vision based on ultra-violet/violet-sensitive UV/V cones expressing short wavelength-sensitive opsin 1 (SWS1), S cones expressing short wavelength-sensitive opsin 2 (SWS2), M cones expressing medium wavelength-sensitive opsin (RH2) and L cones expressing long wavelength-sensitive opsin (LWS). Double cones (D) express LWS but do not contribute to colour vision. Each cone is equipped with an oil droplet, transparent in UV/V cones, but pigmented by carotenoids: galloxanthin in S, zeaxanthin in M, astaxanthin in L and a mixture in D cones. Owls (Strigiformes) are crepuscular or nocturnal birds with rod-dominated retinae and optical adaptations for high sensitivity. For eight species, the absence of functional SWS1 opsin has recently been documented, functional RH2 opsin was absent in three of these. Here we confirm the absence of SWS1 transcripts for the Long-eared owl (Asio otus) and demonstrate its absence for the Short-eared owl (Asio flammeus), Tawny owl (Strix aluco) and Boreal owl (Aegolius funereus). All four species had transcripts of RH2, albeit with low expression. All four species express all enzymes needed to produce galloxanthin, but lack CYP2J19 expression required to produce astaxanthin from dietary precursors. We also present ocular media transmittance of the Eurasian eagle owl (Bubo bubo) and Short-eared owl and predict spectral sensitivities of all photoreceptors of the Tawny owl. We conclude that owls, despite lacking UV/V cones, can detect UV light. This increases the sensitivity of their rod vision allowing them, for instance, to see UV-reflecting feathers as brighter signals at night.

Vocal individuality has been used as a monitoring tool, and two criteria are a prerequisite: high variation among individuals and low variation within individuals, and vocal consistency within and across seasons. We examined individual variation in the territorial hoot calls of the tawny owl (Strix aluco) to discriminate between males and to assess a possible conservation technique that would allow for monitoring individuals within a study area. The territorial calls were recorded from five males in the Naejang Mountain National Park in South Korea during the breeding season in 2015 and 2016 and analyzed both quantitatively and qualitatively to determine the amount of variation within and between individuals. Our results showed that the territorial calls were specific to individuals within a population and that the acoustic distances between males living in the same territory during the two years were the smallest for the four nesting sites. Our results suggest that territorial calls of the tawny owls are individually identifiable over two years and that this acoustic technique can be useful for monitoring individual site fidelity.

The aim of this study was to identify possible predisposing anatomical factors associated with humeral fractures in birds of prey through comparison of specific anatomical features in different raptor species. An anatomical study of bone features in birds of prey was performed on 3 male subjects from 5 different species. The selected species included in this investigation were 3 diurnal species (the common buzzard [Buteo buteo], the peregrine falcon [Falco peregrinus], and the European honey-buzzard [Pernis apivorus]) and 2 nocturnal species (the barn owl [Tyto alba] and the tawny owl [Strix aluco]). Humeral bone samples were tomographically analyzed with a micro–macro-focus computed tomographic machine. Specific humeral anatomical points were selected (foramen pneumaticum and tuberculum dorsale for the proximal humerus; corpus humeri for the diaphyseal humerus; and above the condylus dorsalis for the distal humerus) to measure foramen pneumaticum diameter (in millimeters), cortical thickness (in millimeters), and trabeculae number and sizes (in millimeters). Apparent density, measured with the Hounsfield unit, was used to assess the degree of bone resistance. Statistical analysis was performed with a Spearman's correlation, and significance was set at P < .05. The differences among the observed bone volumes were highly significant (P = .00). Trabeculae number and the humeral anatomical point measurements showed differences in all 5 avian species investigated. However, those differences were not significant, except at the condylus dorsalis; in which, a significant interspecies difference (P = .002) was recorded. Trabecular size, cortical thickness, bone density, and diameter of the foramen pneumaticum were all different in all raptor species; however, these variations were not significant. The study confirms the existence of humeral bone volume differences between diurnal and nocturnal species. Furthermore, the data suggest that the humeri of peregrine falcons and European honey-buzzards may be stronger than the humeri of common buzzards, tawny owls, and barn owls.

This paper reports the rediscovery of the type specimens (holotype and paratype) of Strix aluco volhyniaeDunajewski, 1948, a junior synonym of Strix aluco aluco Linnaeus, 1758. Previously thought to have been destroyed during the Second World War, the types were found in the collection of the Museum and Institute of Zoology of the Polish Academy of Sciences. Additionally, this paper provides support for the availability of the name Strix aluco volhyniae, which was initially proposed as a new race.

Telomere erosion has been proposed to be tightly associated with senescence, environmental stressors and life history trade-offs. How telomere dynamics vary across life stages and especially in relation to (heritable) phenotypic traits is still unclear. The tawny owl Strix aluco display a highly heritable melanin-based colour polymorphism, a grey and a brown morph, linked to several fitness traits including morph-specific telomere dynamics. As adults, brown tawny owls have shorter relative telomere length (RTL) and exhibit faster telomere shortening rate than grey owls. Here we test if these morph-specific telomere dynamics emerge already during growth, or if they are induced only in adult life through differential physiological costs associated with the life history of the morphs. We analysed RTL from 287 tawny owl offspring and 81 first breeding adults to evaluate at what life stage morph-specific patterns emerge. We found no differences in RTL between the two morphs during the nestling period nor at the first breeding attempt. Sex, brood size or size rank in the nest did not affect offspring RTL. Among first-breeders, females had shorter telomeres than males suggesting a sampling-time dependent difference in reproductive costs between sexes, due to the prominent sex roles in tawny owls in the early nestling period. The probability to return to breed after the first breeding attempt was not affected by RTL, sex or colour morph. The lack of morph-specific difference in RTL among nestlings and first breeders suggests that previously observed morph-specific differences in RTL dynamics in adults emerge at the onset of the breeding career and is likely due to different physiological profiles and life-history strategies adopted by adults. We conclude that different telomere dynamics and senescence patterns among highly heritable phenotypes (colour morphs) are likely to be a result of differential costs of reproduction and self-maintenance. (Less)

espanolLa comunidad de micromamiferos (ordenes Rodentia y Eulipotyphla) fue evaluada en una sola localidad cercana a la costa catalana, en relacion con los cambios antropicos en el uso del suelo. La baja detectabilidad de algunas especies nos condujo a evaluar el conjunto de micromamiferos analizando egagropilas de lechuza comun (Tyto alba) extraidas del mismo punto de anidacion durante un periodo de treinta anos. Los objetivos fueron: 1) describir las variaciones paisajisticas, 2) documentar cambios en la comunidad de micromamiferos y 3) relacionar estos cambios con los paisajisticos. La riqueza en especies no parecio variar con los cambios en el uso del suelo, sin embargo, cuando estas se separaron en gremios (abierto, forestal y antropico), se pudieron observar diferencias significativas. El gremio abierto disminuyo en un 6%, mientras los gremios forestal y antropico se incrementaron un 5% y un 2% respectivamente. El abandono de terreno cultivable, la expansion de areas forestales y el incremento en urbanizacion se vieron vinculados a estos cambios en los gremios, mientras que las especies, de forma individual, mostraron cambios relacionados con los climaticos. La perdida de habitat abierto adecuado para este ave se vio reflejada en la sustitucion de la lechuza por el carabo comun (Strix aluco), ocupando su lugar de anidacion. Por lo tanto, el seguimiento de la lechuza comun resulta ser una herramienta util para analizar respuestas al entorno en la comunidad de micromamiferos, posibilitando planes de conservacion mas viables y especificos para ambos. EnglishThe small mammal community (Orders Rodentia and Eulipotyphla) was evaluated in one single locality in coastal Catalonia in relation to human-induced changes in land use. Low detectability of some species drove us to assess the small mammal assemblages analysing barn owl (Tyto alba) pellets sampled in the same nesting site for a period of thirty years. The objectives were to 1) describe variations in landscape use, 2) document small mammal community changes and 3) relate these changes to those in land use. Species richness did not seem to vary with changes in land use, however, when species were separated into guilds (open, forest and synanthropic), significant differences could be observed. The open guild decreased by 6%, while the forest and synanthropic guild increased by 5% and 2% respectively. Abandonment of arable land, expansion of forested areas and an increase in urbanisation were closely linked to these guild changes, while some individual species showed variations which paralleled climatic changes. Loss of adequate open habitat for this raptor was highlighted by a species substitution, with the tawny owl (Strix aluco) occupying the nesting site previously used by the barn owl during the last years of the study. Barn owl diet monitoring therefore proves to be a useful tool to analyse small mammal community responses to changes in the environment, allowing for more specific and viable conservation plans for both small mammals and barn owls.

Over a two-year period (2013–2015), we trapped and radio-tracked 20 Tawny Owls at two study sites in northern Spain. We obtained 4257 radio-tracking locations, 328 of which were associated with voc...

The aim of this study was to describe how the diet of tawny owl changed along an urbanisation gradient. The research was conducted from 2003 to 2011 in central Poland. Pellets were collected in the following zones: the center of Warsaw, capital city of Poland (inhabited by approximately 2 million people), its outskirts and rural areas beyond the city. To investigate the differences in the percentages of the main groups of prey between the three zones, a redundancy analysis (RDA) method was implemented using CANOCO software. Sparrows, rats, pine voles and striped field mice were most connected to the city center, whereas voles (all species pooled together), northern birch mice, hazel dormice and insects were more commonly found among prey items collected in rural areas. As the outskirts were transitional areas where different habitats typical for both rural areas (such as forest complexes) and urban areas (such as parks or built-up areas) were present, no prey group was strongly connected to this landscape. Mammals were dominant in the diet in winter in all habitat types. Their share ranged from 52% (in the city center) to approximately 90% in the outskirts and rural areas. Birds, amphibians, reptiles and insects were more frequent in summer. Overall, the study confirmed high plasticity of the species as an opportunistic predator and its ability to adapt to long-term changes in its main prey in most urbanized areas.

To use vocalizations properly for the estimation of owl population size, it is important to identify how environmental factors affect owl calling behaviour. Here, we analyse how intrinsic and extrinsic factors modify the vocal activity of Tawny Owls Strix aluco in two areas of northern Spain. From March 2013 to May 2015, we radiotracked 20 Tawny Owls and also undertook a systematic survey in which we collected data on spontaneous vocal activity (hoot/call) of the tagged owls, plus their mates and neighbours (36 untagged owls). After 223 nights in Valle de Mena and 224 in Duranguesado we obtained a total of 8791 records of vocal activity. The annual proportion of surveys on which an owl called was 6.3% and did not differ between the study areas. Vocal activity of Tawny Owls varied with sex, annual cycle stage and weather. Male owls were significantly more vocal than females year‐round, and vocal activity peaked during the incubation and post‐breeding periods. Wind and rain adversely affected vocal activity of both sexes throughout the year. Tagged owls were detected more often than untagged owls, which we interpret as an observer effect because the systematic survey ensured that short distances to tagged owls increased the probability of detecting vocal activity. In fact, 2.8% of variation in vocal activity was due to detectability differences between tagged and untagged owls. We conclude that if fieldwork is carried out during the optimum period of the year for vocal detection (i.e. incubation, which in our case was around mid‐April), and under good weather conditions (dry and calm nights), censuses based on spontaneous vocal activity would detect only approximately 12% of the true Tawny Owl population.

Loss of favorable habitats for species due to temperature increase is one of the main concerns of climate change on the ecosystem, and endangered species might be much more sensitive to such unfavorable changes. This study aimed to analyze the impact of future climate change on endangered wild animals in South Korea by investigating thermal sensitivity and vulnerability to temperature increase. We determined thermal sensitivity by testing normality in species distribution according to temperature. Then, we defined the vulnerability when the future temperature range of South Korea completely deviate from the current temperature range of species distribution. We identified 13 species with higher thermal sensitivity. Based on IPCC future scenarios RCP 4.5 and RCP 8.5, the number of species vulnerable to future warming doubled from 3 under RCP4.5 to 7 under the RCP8.5 scenario. The species anticipated to be at risk under RCP 8.5 are flying squirrel (Pteromys volans aluco), ural owl (Pteromys volans aluco), black woodpecker (Dryocopus martius), tawny owl (Strix aluco), watercock (Gallicrex cinerea), schrenckʹs bittern (Ixobrychus eurhythmus), and fairy pitta (Pitta nympha). The other 10 species showing very narrow temperature ranges even without normal distributions and out of the future temperature range may also need to be treated as vulnerable species, considering the inevitable observation scarcity of such endangered species.

OBJECTIVE To determine endothelial cell density (ECD) and morphology and morphometry of corneal endothelial cells in the tawny owl (Strix aluco), as well as to report the effects of aging on these parameters. ANIMAL STUDY AND PROCEDURES Twenty tawny owls were included in the study and classified into 2 groups according to their age: fledglings ( 1 year old). Central corneal endothelium was studied by means of noncontact specular microscopy (Specular Microscope SP-2000P; Topcon, Tokyo, Japan), and results for ECD (cells/mm2 ), mean cell area ((MCA (μm2 )), polymegathism (CV), and pleomorphism (% hexagonal cells) were obtained. Results are described by median, interquartile range (25th, 75th percentiles), and absolute range for ECD, MCA, pleomorphism, and polymegathism. In addition, inferential analyses by Mann-Whitney U test were also performed. A two-tailed Type I error of 5% was established. RESULTS Results in fledglings were as follows: ECD = 2864 cells/mm2 , MCA = 348 μm2 , % hexagonal cells = 72.75%, and CV = 21. Results in adults were as follows: ECD = 2602 cells/mm2 , MCA = 384 μm2 , % hexagonal cells = 78.83%, and CV = 16. No significant differences in ECD and MCA were seen between the groups (P > .05), although there were significant differences in % hexagonal cells and CV (P

During the years 2008–2014, we studied diet composition, the number of breeding pairs, and reproductive output of tawny owls in Central Europe (Czech Republic) in relation to availability of main prey in the field. We also performed a meta-analysis on diet composition of tawny owl in Europe that confirmed the important role of Apodemus mice in tawny owl diet in Central Europe. In concordance, Apodemus mice were the main prey of tawny owl in our study area (38.7%), and Microtus/Myodes voles (15.4%), birds (12.1%) and others (33.8%) were alternative prey. We found a positive relationship between the proportion of Apodemus mice in the diet and their abundance in the field (beta = 0.23, P = 0.001). Availability of main prey (Apodemus mice, Microtus/Myodes voles or Sorex shrews) in the field was not correlated with the number of breeding pairs. Proportion of birds in diet (expressed by scores from multivariate analysis), which was inversely related to proportion of Apodemus mice, was positively correlated with laying date (beta = 0.66, P = 0.012) and negatively correlated with clutch size (beta = − 0.45, P = 0.004) and brood size (beta = − 0.16, P = 0.076). We also found negative relationships between laying date and clutch size (beta = − 0.13, P = 0.014) and brood size (beta = − 0.07, P = 0.057). Our results support the idea that diet and breeding ecology of owls in Central Europe is mainly driven by the availability of Apodemus mice that are suitable prey due to their similar habitat requirements and nocturnal activity.

In this study, we determined the concentrations of As, Cd and Pb in the shaft of all primary flight feathers from ten tawny owl (Strix aluco) specimens, with the aim of selecting which shaft of the corresponding primary feather should be used in biomonitoring surveys to enable inter-individual comparisons of the levels of these metals. The birds had died between 2006 and 2013 and their bodies were stored in the various Wildlife Recovery Centres in Galicia (NW Spain). The analyses revealed a high degree of inter-shaft variability, mainly in the concentrations of As and Cd. However, it was possible to identify the most representative samples in each case: for As, the shaft of primary flight feather number 5 (S5) (which represented 11% of the total As excreted in all of the primary flight feathers); for Cd, the shaft of primary flight feather number 2 (S2) (11% of the total excreted); and for Pb, the shaft of primary flight feather number 8 (S8) (14% of the total excreted). However, the difficulties associated with the analytical determination of these pollutants in the shaft should be taken into account when this technique is applied in biomonitoring studies.

An increasing urbanization of habitats in which birds live influences their populations by modifying behaviour, dietary composition, causes of mortality and variables related to breeding. This study aimed to compare breeding periods and productivity among tawny owls, Strix aluco, inhabiting either an urban or an extra-urban area. Studies were conducted in parallel in two locations: central zone of Warsaw – the Polish capital – and the Rogow Forest – ca 70 km west of Warsaw. Number of fledglings and the beginning of the breeding period was assessed by direct observations and listening to calls of juveniles within tawny owl territories. Birds in the urban area were found to start breeding significantly earlier (from 5th February) than those in the extra-urban area (from 17th March). However, the two populations proved to be similarly productive, with 3.2 or 3.4 young per nest on average. The phenomenon of early breeding in city dwelling birds was confirmed in other tawny owl populations as well as other bird species. It can be potentially driven by factors such as higher temperature, artificial light and rich and stable food base.

Paleoenvironmental reconstructions based on micromammalian assemblages are a commonly used tool in paleoecology and zooarcheology. However, predator prey preferences may bias these assemblages to an unknown degree, thus leading to unreliable paleoenvironmental reconstructions. While attempts at taxonomically identifying micromammal predators through taphonomy has been conducted in the past, none has satisfactorily differentiated between owl taxa. Here we introduce the novel postcranial fracture index and revised versions of digestion indices for obtaining higher taxonomic resolution in taphonomic signatures. We taphonomically analyzed bone assemblages created by owls both in controlled feeding experiments and in the wild. We used blind experiment methodology involving multiple experimenters (each analyzing different bones) to test known and novel indices for reproducible taphonomic signatures within five species of owls (Tyto alba, Asio otus, Athene noctua, Bubo bubo and Strix aluco), Falco tinnunculus and Vulpes vulpes for comparison. We found that experimenter identity has a profound impact on the digestion indices. Nonetheless, the breakage indices and our novel fracture index found significant differences and subjective differences between owl species. Mandible breakage differentiated between Tyto alba and the other, more destructive owls. Postcranial breakage distinguished Strix aluco from the other owls. The postcranial fracture index differentiated between all species except between Athene noctua and Bubo bubo. We recommend a combination of taphonomic indices as a reliable tool for inferring owl species identity of micromammal assemblages.

Species distributional data from atlas projects collected by volunteers and professionals play an essential role in ecology and biodiversity conservation. Atlas data primarily allow evaluating longitudinal and latitudinal gradients in species distribution. However, the effects of additional factors such as elevation and associated climatic conditions and landscape structure are rarely assessed. We used the original data from the Atlas of birds breeding in the Czech Republic in terms of the presence and absence (0/1) of breeding occurrence of seven owl species in 604 mapping quadrates (each quadrate 12.0 × 11.1 km in size) to assess the effect of elevation (reaching from 100 to 1100 m a.s.l.) and temperature on the distributional patterns of the owls. Using a multivariate spatial analysis with latitude and longitude as space predictors and landscape structure as covariates, we found that elevation and temperature significantly affected owl distribution; the model explained 94.8% of the variability (p = 0.002). Only the boreal owl (Aegolius funereus) showed a clear preference for the highest elevation, and simultaneously, boreal and pygmy (Glaucidium passerinum) owls preferred the coldest environments. Eagle owl (Bubo bubo) and tawny owl (Strix aluco) most often occupied low and middle elevation of moderate temperatures. Barn owl (Tyto alba) and long-eared owl (Asio otus) inhabited the warmest areas in low elevations. Finally, little owl (Athene noctua) most often occurred in the lowest elevations of intermediate temperatures. We have documented that the elevation and associated climate conditions can work as an effective predictor to assess distributional preferences of owl species based on atlas data. The findings can be helpful when the management of owls' habitats is considered and implemented. For example, the results of our case study suggest that the boreal owl can be susceptible to global warming and intensive logging at high elevations.

The aim of the study was to describe the species diversity of small mammals in the western part of the Skierniewice Forest District (Central Poland) using tawny owl (Strix aluco) pellets. The landscape itself is a field and forest mosaic with small forest complexes. Four forest complexes with an area between 70 and 750 ha and surrounded by arable lands as well as loosely scattered buildings were chosen to carry out our work in. Owl pellets were collected in the years 2014–2016 and examined for small mammal remains employing standard protocols.Altogether, we identified 963 items belonging to 17 different mammalian prey species. The most numerous was the yellow-necked mouse,Apodemus flavicollis, which accounted for 33.5% of all identified items. As the second most important group, voles (Microtusspp.) accounted for 12.8% of all identified mammals. Unfortunately, we were unable to find species considered rare in central Poland, i.e. hazel dormouse,Muscardinus avellanarius, European water vole,Arvicola amphibiusand field vole,Microtus agrestis.In overall, the species composition of small mammal assemblages in the studied area was similar to adjacent regions.

Capsule: Tawny Owls Strix aluco occupying nest boxes preferred habitats which were positively associated with the probability of nesting success.Aims: We aimed to determine whether or not: (1) Tawny Owls showed habitat preferences when occupying nest boxes; (2) nesting performance was related to the habitats around occupied nest boxes and (3) habitat availability had changed around available and occupied nest boxes between 1995–2004 and 2005–14.Methods: Tawny Owls were studied using nest boxes erected in a commercial forest. During nest boxes checks (724 cases), data on occupancy and nesting performance (88 cases) were recorded, and habitat within a 0.4 km radius around nest boxes was analysed.Results: Tawny Owls had preferences for clearings within forests, mature forests and grasslands but avoided young forests. We found a positive relationship between nesting success and abundance of clearings within the forest, and a negative relationship between nesting success and abundance of young forests....

Censusing nocturnal species such as the Tawny Owl (Strix aluco) living in a dense population can lead to an overestimate if individual signatures are not available. A technique that separates the individualistic call of the Tawny Owl could be a useful tool for an exhaustive census. Six Tawny Owl males were followed for nine months; 654 vocalizations were analysed. Three methods – Spectrographic Cross Correlation (SPCC), Acoustic Space (AS) and Visual Spectrogram Comparison (VSC) – were tested to assess their ability to classify the typical male call. For SPCC, 10 randomly selected hoots for each male were compared: the distributions of correlation coefficients differed in only 26.7% of the cases when intra and inter individual variability are compared. For AS, all the spectrograms were measured through 13 parameters and intra and inter individual distances were compared: the interval containing 95.4% of intra-individual measures also contained 95.9% of inter-individual comparisons. Both SPCC and A...

Capsule: The use of call-broadcasting significantly increases the number of Tawny Owls Strix aluco detected in winter point counts, but requires careful survey design to avoid introducing potential sources of bias into population estimates.Aims: To examine Tawny Owl response to call-broadcasting to aid survey design in national monitoring efforts.Methods: A nocturnal survey was undertaken at 36 survey points over three nights in winter in Thetford Forest, England. Each survey consisted of four consecutive five-minute segments: a passive count, followed by three counts with the use of call-broadcasting.Results: Few (4%) Tawny Owls were recorded during passive surveys, whereas the greatest response was during the first and second call-broadcast segments (49% and 36%, respectively). New detections declined to 11% in the final segment. Response was fastest at dusk, although time of night did not significantly affect the number of individuals detected. Male owls accounted for 79% of detections.Conclusi...

Established taxa within the Enterobacteriaceae wereisolated from cloacal swabs of Strix aluco chicks in nest boxes located at five research sites. ChromID ESBL medium (bioMerieux) was used to select a pool of Enterobacteriaceae strains producing extended-spectrum beta-lactamases. Drug sensitivity of the chosen strains was determined from the full pool of Enterobacteriaceae to 6 chemotherapeutics of different mechanisms of action. The study evaluated the sensitivity of ESBL-synthesizing isolates to substances belonging to penicillins, cephalosporins, cephamycins, clavams, carbapenems and monobactams. Analysis of the results indicated a potential role of Strix aluco in the dissemination of epidemiologically-relevant Enterobacteriaceae, and, importantly, pose health risks to forest service workers, nature protection service and ornithologists. The results can also serve as the basis for further environmental studies.

The Tawny Owl (Strix aluco) is the most abundant nocturnal raptor in Europe. It has been thoroughly studied in various regions, but its habitat preferences in Mediterranean environments remain poorly understood. With the aim to present novel information about this aspect of the ecology of the Tawny Owl, we established 115 survey stations in the Special Conservancy Area 'Sierras de Talayuelas y Aliaguilla' (Castilla-La Mancha region, eastern Spain) and carried out nocturnal surveys by recording spontaneous calls and vocal responses to call playbacks. We then assessed environmental characteristics (vegetation types, soil type, altitude, potential competitors, and anthropic disturbance) in areas where owls were detected or not detected during the breeding season. Overall, we detected 60 responding owls at 49 survey stations during breeding season in the study area (i.e., density 1.22 owls/km2). We found that Tawny Owls preferred lower altitudes and patchy heterogeneous areas. Owls seemed to avoid natural grasslands and areas characterized by limestone soils and associated vegetation, and preferred areas characterized by clay soils and associated vegetation. Interestingly, we did not detect owls close to wind farms, which seem to create a buffer effect on owls' occurrence. The noise generated by the turbines might be a limiting factor that could account for this avoidance. Our multivariate results showed that Tawny Owls preferred heterogeneous patchy habitat but avoided non-irrigated arable land. Tawny Owls inhabit Mediterranean landscapes where conditions are favorable, but human activities such as wind farms may limit their distribution. Additional research is needed to determine the drivers of this avoidance and whether Tawny Owls also avoid wind farms in other regions of their range.

Urbanization and its inherent road network are one of the major movements that impulse landscape and biodiversity change, and its effects have yet to be fully understood. Few works focus on the effect of this urbanization on abundance and population trend of a certain species, as this study does, using the tawny owl (Strix aluco) as our case study. Although the tawny owl is not threatened at European or global scale, it is often found roadkilled. We studied the effects of different road types on tawny owl abundance in southern Portugal, from 2005 to 2016. In woodlands far from roads, we found high tawny owl abundance, a stable population trend, and low variation in site occupancy. On the contrary, main roads disrupted habitat quality for tawny owls—limiting their abundance and site occupancy and leading to a negative population trend due to disturbance and/or mortality. Secondary roads did not severely disrupt habitat quality, allowing initial occupation and relatively high densities, yet they may act as ecological traps, revealing instability in occupation along the breeding season and a negative population trend. Tawny owl individuals may settle near secondary roads while waiting for a vacant space in woodlands far from roads (the prime high-quality habitats). To avoid the negative effects of roads on tawny owl populations, mitigation efforts should be applied to both main and secondary roads.

In the present study, we used 37-year long dataset on Tawny Owls from the annual monitoring of nestboxes at a sample plot in Central Lithuania. We expected that Tawny Owls responded to changes in land use practices, stemming from a change in both political and economic system, which may affect prey abundance and composition, breeding performance and demography. To analyze temporal changes in monitored parameters, we divided the study period into three phases (1978–1989, 1990–2001 and 2002–2014), corresponding to different socio-economic conditions. The number of nesting pairs of Tawny Owls decreased significantly in the last 13 years of the study, but the number of successful pairs fluctuated without any trend. The clutch size and number of nestlings varied without significant trends, but nesting success improved over the last 13 years. Annual apparent survival probability of the female Tawny Owls did not vary significantly over the study period (model averaged values between 0.71 and 0.73). Owl...

Some studies suggest that mild winters decrease overwinter survival of small mammals or coincide with decreased cyclicity in vole numbers, whereas other studies suggest non-significant or positive relationships between mild winter conditions and vole population dynamics. We expect for the number of voles to be higher in the rich and low-lying habitats of the coastal areas than in the less fertile areas inland. We assume that this geographical difference in vole abundances is diminished by mild winters especially in low-lying habitats. We examine these relationships by generalized linear mixed models using prey remains of breeding tawny owls Strix aluco as a proxy for the abundance of voles. The higher number of small voles in the coastal area than in the inland area suggest that vole populations were denser in the coastal area. Vole populations of both areas were affected by winter weather conditions particularly in March, but these relationships differed between areas. The mild ends of winter with frequent fluctuations of the ambient temperature around the freezing point (“frost seesaw”) constrained significantly the coastal vole populations, while deep snow cover, in general after hard winters, was followed by significantly lowered number of voles only in the inland populations. Our results suggest that coastal vole populations are more vulnerable to mild winters than inland ones. We also show that tawny owl prey remains can be used in a meaningful way to study vole population dynamics.

The level of PFAS (per- and polyfluorinated alkyl substances) contamination in freshwater and terrestrial Swedish environments in 2013/2014 was assessed by analyzing a range of perfluorinated alkyl acids, fluorotelomer acids, sulfonamides, sulfonamidoethanols and polyfluoralkyl phosphate diesters (diPAPs) in predator bird eggs. Stable isotopes ((13)C and (15)N) were analyzed to elucidate the dietary source. The tawny owl (Strix aluco, n=10) and common kestrel (Falco tinnunculus, n=40), two terrestrial species, and the osprey (Pandion haliaetus, n=30), a freshwater specie were included. In addition, a temporal trend (1997-2001, 2008-2009, 2013) in osprey was studied as well. The PFAS profile was dominated by perfluorooctane sulfonic acid (PFOS) in eggs from osprey and tawny owl, while for common kestrel perfluorinated carboxylic acids (∑PFCA) exceeded the level of PFOS. PFOS concentration in osprey eggs remained at the same level between 1997 and 2001 and 2013. For the long-chained PFCAs, there were a significant increase in concentrations in osprey eggs between 1997 and 2001 and 2008-2009. The levels of PFOS and PFCAs were about 10 and five times higher, respectively, in osprey compared to tawny owl and common kestrel. Evidence of direct exposure from PFCA precursor compounds to birds in both freshwater and terrestrial environment was observed. Low levels of diPAPs were detected in a few samples of osprey (

Owls, like other secretive species, are difficult to detect. During the last few decades, protocols used for surveying owls have revealed the best methods to acquire accurate data about their distribution and abundance. However, these protocols were established by testing the response of owls to playback of broadcast calls, using wild, unknown individuals that were only noticeable when vocalisations were given/detected. Therefore, there is no clear consensus on the best method to survey owls. We tested a protocol to survey Tawny Owls Strix aluco using 20 radio-tracked individuals in two study areas with contrasting owl density. We conducted 58 survey tests during winter 2014-2015. In the two study areas respectively, 61.3% and 70.4% of the target individuals responded, on average, within the first six minutes after the start of call playback. Naive occupancy estimates were 67.7% and 85.2%, respectively, considering the combined responses of the target individual and its mate. We detected a movement of the target owls from their original position towards the playback source on 72.4% of the sampling occasions in both areas. Tawny Owls approached within 50m of the playback point on only 56.9% of occasions. Mates or neighbours responded to broadcast calls more often in the high-density area than in the low density one. The detection probability of target owls increased more than fourfold when their mates joined in defence of the territory, and also increased fourfold when the target individuals approached the broadcast point and when we increased the playback period from five to fifteen minutes. We recommend two 15-minute periods of call playback per point and year, on dry and calm winter nights, at survey points one kilometre apart.—Zuberogoitia, I., Burgos, G., Gonzalez-Oreja, J.A., Martinez, J.E., Morant, J. & Zabala, J. (2020). Testing detectability of radio-tracked Tawny Owls using playback broadcast surveys: designing evidence-based surveys. Ardeola, 67: 355-369.

In 1984–2016 we studied the habitat choice, nest placement and breeding success of Common Buzzard Buteo buteo and Tawny Owl Strix aluco in the municipality of Varberg in southwest Sweden (57°10'N, 12°10'E). The analyses are based on 1,512 successful breeding attempts of Common Buzzard, and 1,387 of Tawny Owl. The average number of young per successful breeding was 1.74 and 2.86, respectively. The variation between years was highly correlated between the two species, suggesting a common food source. In both species the between-year variation in clutch size was particularly large in beech forest territories, most likely caused by the effect of beech mast years on local rodent populations. The breeding density of Common Buzzard was particularly high in 1990–1995, coinciding with large areas of farmland set-aside. In the Common Buzzard, the yearly average number of young per clutch declined significantly with yearly average hatching date.

To analyze extreme sideways turn of the head in owls, a total fresh specimen of Strix aluco was frozen in respective posture and CT-scanned. The maximum turn to one side was found to be 360°, provided that the head is drawn into the shoulders. 160° of this full turn are ensured by the neck axial rotation (this includes ~90° twist of the head relative to epistropheus and, posterior to it, less than 15° per every cervical joint), and the rest 200° are ensured by combination of dorsal and lateral flexion. The 15° limit is overcome in five joints in respect of dorsiflexion, and in six joints in respect of lateral flexion. So large a degree of lateral mobility is unusual among birds, and is appreciated as a crucial adaptation to extreme head turning.

Territorial calls (hooting) of two tawny owl subspecies, Strix aluco aluco (the eastern European subspecies) and Strix aluco willkonskii (the Caucasian subspecies), were recorded from October 2007 to February 2013, to study variation between individuals and subspecies. Calls of the eastern European subspecies were recorded in Moscow region (Russia) and “Gomolshanskie Lesa” National Park (Ukraine). Males of the Caucasian subspecies were recorded in “Bolshoi Utrish” Reserve and “Sochinskii” National Park (Russia). The territorial calls of the eastern European and Caucasian subspecies are compared for the first time. The discriminatory accuracy of individual calls reached 98% for S. a. aluco and 77% for S. a. willkonskii when accounting for six frequency and temporal parameters of their call. We found the call of the two subspecies to differ in half of the acoustic parameters considered, suggesting that macrogeographic variation between the Eastern European and Caucasian subspecies may have taken place.

Eight subspecies have been proposed within the Tawny Owl (Strix aluco) species. However, recent molecular data have challenged this view, encouraging further work in this species complex. Here we reevaluated the taxonomic status between the North-Western African Tawny Owl, S. a. mauritanica, and its closest Iberian Tawny Owl population (from the S. a. sylvatica to S. a. aluco clade) separated by the Strait of Gibraltar. The Tawny Owl is a non-migratory and territorial species, and juvenile dispersal is restricted to a few kilometers around the natal site. This limited dispersal and the barrier imposed by the Strait of Gibraltar predicted a strong differentiation between the two populations. We tested this using DNA barcoding, Bayesian phylogenetic and species delimitation analysis. We found that an 81.1% of variation is due to the intergroups variation. In addition, the inter-intraspecific distances distribution revealed a barcoding gap among the two subspecies. Also, posterior probabilities and the PAB value allowed to reject the hypothesis that observed degree of distinctiveness is due to random coalescence processes. These findings clearly support the Strait of Gibraltar as an isolating barrier for this species. The subspecific status is confirmed and species status is even suggested for S. a. mauritanica.

In colour polymorphic species morphs are considered to be adaptations to different environments, where they have evolved and are maintained because of their differential sensitivity to the environment. In cold environments the plumage insulation capacity is essential for survival and it has been proposed that plumage colour is associated with feather structure and thereby the insulation capacity of the plumage. We studied the structure of contour feathers in the colour polymorphic tawny owl Strix aluco. A previous study of tawny owls in the same population has found strong selection against the brown morph in cold and snowy winters whereas this selection pressure is absent in mild winters. We predicted that grey morphs have a denser and more insulative plumage, enabling them to survive better in cold climate compared to brown ones. The insulative plumulaceous part of the dorsal contour feathers was larger and the fine structure of the plumulaceous part of the feather was denser in grey tawny owls than in brown ones. In the ventral contour feathers the plumulaceous part of the feather was denser in females than in males and in older birds without any differences between morphs. Our study suggests that insulative microscopical feather structures differ between colour morphs and we propose that feather structure may be a trait associated with morph-specific survival in cold environments.

The demographic performance of avian predators is influenced by climate variations. The Plant Area Index (PAI) is considered a key descriptor of the (evolving) vegetation sensitive to climate and soil aridity and drought stress. To assess if the increased aridity regime in the mediterranean region affects the reproduction of a forest predator, the breeding success of the Tawny Owl Strix aluco was studied over 7 years (1997–2003) in Castelporziano, central Italy. The inter-annual fluctuations in owl demographic output observed in neighbor forest and agricultural sites were compared with climatic variables (rainfall, minimum and maximum air temperature, aridity index) and changes in the PAI estimated by satellite imagery. Out of 326 breeding attempts, the percentage of successful pairs per year ranged between 4 and 28 %, the number of fledglings per successful pair ranged between 1.0 and 1.8 and breeding rate (i.e. the number of fledglings per breeding pair) ranged between 0.1 and 0.4. Demographic, climatic and remotely sensed indexes showed coherent variations among years. Rainfall and lower aridity index are associated with a higher breeding success. The relationship between PAI and breeding rate was found significant only in forest sites. Results suggest that Tawny Owls may positively respond to drier weather conditions by reducing the breeding rate.

Secondary exposure of predators to anticoagulant rodenticides, and in particular second generation anticoagulant rodenticides (SGARs), is a global phenomenon. The widespread and large-scale nature of this exposure has attracted considerable concern, although the consequences in terms of likelihood of poisoning of individuals and resultant impacts on populations are not well characterised. Secondary exposure of predators may as rise from once or more of: (i) eating contaminated commensal rodents subject to control (target species are typically rats and house mice); (ii) consumption of contaminated non-target small mammals (such as Peromyscus, Microtus, and Apodemus species) that encounter and feed on what are rodent-attractive baits; (iii) consumption of non-rodent vertebrate and invertebrate prey that may also incidentally encounter and eat baits. We hypothesised that predators feeding primarily on target species may be most at risk of exposure to SGARs while those predominantly taking non-mammalian prey may be at least risk. We tested this hypothesis by comparing exposure, determined from the presence and magnitude of SGAR liver residues, in red kites (Milvus milvus), which feeds extensively on rats, in barn owls (Tyto alba), kestrels (Falco tinnunculus), and tawny owls (Strix aluco) that feed widely on non-target small mammals, and in sparrowhawks (Accipiter nisus) that feed predominantly on small birds. We found that the scale and magnitude of exposure was broadly consistent with our hypothesis, and that controlling for age in the analysis could be important as older birds can accumulate residues with age. However, exposure in kestrels was typically greater than that in barn owls and tawny owls, despite what is thought to be a general similarity among the species in their diets. We discuss the relative importance of trophic pathways relative to other factors that may drive secondary exposure in predators, and confirm that species that feed on rats or other target species may be at most risk of exposure and poisoning.

Concentrations of different heavy metals (As, Cd, Cr, Cu, Hg, Pb, Zn) were examined in the contour feathers of long-eared owl (Asio otus), little owl (Athene noctua), tawny owl (Strix aluco), barn owl (Tyto alba), Eurasian sparrowhawk (Accipiter nisus), rook (Corvus frugilegus), hooded crow (Corvus cornix), carrion crow (Corvus corone), common buzzard (Buteo buteo) and barn swallow (Hirundo rustica). The samples were collected from the Hortobagyi Madarpark (Bird Hospital Foundation) in Hungary. The bird species were classified into six groups based on their nourishment. Feathers were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The aim of our study was to determine the concentration of the above-mentioned heavy metals in the six different groups and to compare them by the groups, to find a possible connection between the concentrations and the age of birds and to get some information about the heavy metal burden of the environment. The highest As concentration was measured in little owl (0.65 ± 0.56 mg/kg). The highest Cd, Cr and Pb concentration was found in the feathers of barn swallow (0.13 ± 0.06 mg/kg; 1.69 ± 0.44 mg/kg; 5.36 ± 1.46 mg/kg), while the highest Cu and Hg concentration (65.45 ± 17.66 mg/kg; 2.72 ± 1.08 mg/kg) in sparrowhawk feathers and the highest Zn concentration in owls (157.21 ± 57.3 mg/kg). Statistically significant difference has been determined between the juvenile and adult crows in the case of Cd (p = 0.011). The higher concentration was measured in adults (0.14 ± 0.04 mg/kg) than that in juveniles (0.08 ± 0.02 mg/kg). Based on our results, the examined area is not contaminated by these heavy metals on that level, which can cause any adverse effect or poisoning in birds, so this region is safe to wildlife.

We analyzed seasonal changes in Tawny Owl (Strix aluco) diet in a broadleaved forest in Eastern Ukraine over 6 years (2007-2012). Annual seasons were divided as follows: December-mid-April, April-June, July-early October, and late October-November. In total, 1648 pellets were analyzed. The most important prey was the bank vole (Myodes glareolus) (41.9%), but the yellow-necked mouse (Apodemus flavicollis) (17.8%) dominated in some seasons. According to trapping results, the bank vole was the most abundant rodent species in the study region. The most diverse diet was in late spring and early summer. Small forest mammals constituted the dominant group in all seasons, but in spring and summer their share fell due to the inclusion of birds and the common spadefoot (Pelobates fuscus). Diet was similar in late autumn, before the establishment of snow cover, and in winter. The relative representation of species associated with open spaces increased in winter, especially in years with deep snow cover, which may indicate seasonal changes in the hunting habitats of the Tawny Owl.

Males can through their behavior (e.g., courtship feeding) exert an indirect effect on their partner’s reproductive traits, such as the seasonal timing and size of her clutch. Evidence for such indirect (male) effect on reproduction is starting to accumulate. We quantify female and male effects on reproduction in the tawny owl Strix aluco using a hierarchical mixed model on data collected in 1978–2013. We find that differences between males explain 7 % of the phenotypic variance in laying date (females 5 %). In contrast, females have a clear (11 %) effect on clutch size, whereas males have no effect. Based on multivariate hierarchical modeling, we find an individual-level correlation between the male-specific effect on laying date and his body mass (but not his plumage color or wing length). Heavy males may be able to affect their partner’s seasonal timing of laying because of an advantage in providing courtship feeding prior to reproduction. Our findings illustrate that males can be an important determinant of variation in reproduction and that multivariate mixed models present a general approach to pinpoint which individual characteristics could be associated with such indirect effects.

Accumulation of persistent organic pollutants (POPs) in wildlife may be influenced by the physical and biotic environment, and concentrations vary greatly among areas, seasons, and individuals. Different hypotheses about sources of variation in perfluoroalkyl substance (PFAS) concentrations were examined in eggs (n = 107) of tawny owls (Strix aluco) collected over a 24-yr period (1986–2009) in Norway. Predictor variables included the North Atlantic Oscillation (NAO), temperature, snow, food availability (vole abundance), and individual traits such as age, body condition, and clutch size. Concentrations of both perfluoro-octane sulfonate (PFOS) and perfluoroalkyl carboxylates (PFCAs) varied several fold in the population, both inter- and intra-annually. Moreover, individuals laid eggs with several times higher or lower PFAS concentrations within few years (1 yr–5 yr). After controlling for temporal trends (i.e., declining PFOS and increasing PFCA concentrations), both PFOS and PFCAs were positively associated to the winter NAO in the previous year (NAOy – 1), suggesting that atmospheric transport may be affecting the input of PFASs to the local ecosystem. Perfluoro-octane sulfonate was negatively related to temperature, but the pattern was complex as there was an interaction between temperature and the feeding conditions. The PFOS accumulation was highest in years with high vole abundance and low to medium temperatures. For PFCAs, there was an interaction between NAOy – 1 and feeding conditions, suggesting that strong air transport toward Norway and high consumption of voles led to a moderate increase in PFCA accumulation. The individual traits, however, had very little impact on the concentrations of PFASs in the eggs. The present study thus suggests that annual variation in environmental conditions influences the concentrations of PFASs in a terrestrial raptor such as the tawny owl. Environ Toxicol Chem 2015;34:184–191. © 2014 SETAC