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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...

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.

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...

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...

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.

Oropharyngeal trichomonad isolates of wild birds from Spain were studied. A total of 1688 samples (1214 of predator birds and 474 of prey species) from wildlife recovery centres and scientific bird-ringing campaigns were analysed from 2011 to 2013. The overall infection prevalence was 20.3% (11.4% in predator birds and 43.3% in prey species). Pathognomonic lesions were present in 26% of the infected birds (57.3% in predator birds and 4.9% in prey species). The most commonly parasitized species were the goshawk (Accipiter gentilis, 74.5%) and the rock pigeon (Columba livia, 79.4%). Host species in which the parasite has not been previously analysed by polymerase chain reaction and sequencing in Spain are also reported: Columba palumbus, Streptopelia turtur, Pica pica, A. gentilis, Accipiter nisus, Asio otus, Bubo bubo, Buteo buteo, Circus aeruginosus, Circus cyaneus, Falco naumanni, Falco peregrinus, Neophron percnopterus, Otus scops, Pernis apivorus and Strix aluco. Sequence analysis of the ITS1/5.8S/ITS2 region revealed five different genotypes and also some mixed infections. A relationship between genotype and host species was observed, but only two genotypes (ITS-OBT-Tg-1and ITS-OBT-Tg-2) were widely distributed. Genotype ITS-OBT-Tg-1 was most frequently found in predator birds and statistically associated with pathognomonic lesions. Non-strict ornithophagous species were at higher risk to develop disease than ornithophagous ones. Genotypes ITS-OBT-Tcl-1 and ITS-OBT-Tcl-2 are new reports, and ITS-OBT-Tvl-5 is reported for the first time in Spain. They showed higher genetic homology to Trichomonas canistomae and Trichomonas vaginalis than to Trichomonas gallinae, indicating the possibility of new species within this genus.

This study presents the concentration of mercury in feathers of 40 owls (five species) in five regions of Iran. Results showed that mercury concentration in Tawny owl’s feathers ( Strix aluco ) were significantly higher than in the Little owl (Athena noctua) , Eagle owl ( Bub bubo ), Long-eared owl ( Asio otous ) and Short-eared owl (Asio flammeus). Also, mercury concentrations in owl feathers collected from the north of Iran were significantly higher than others regions. Furthermore, mercury concentrations in owl feathers obtained in this study were higher than other regions in the world except for Sweden. This study demonstrates that mercury concentrations in Iranian owls, with the exception of the Tawny owl, are below toxic concentration (5 mg kg -1 ). In addition, location was a contributing factor in the mercury concentration in Iranian owl’s feathers. Keywords: owl, Iran, mercury, featherswww.chemspecbio.co.uk INTRODUCTION Mercury occurs naturally in the environment but anthropogenic sources, such as fossil fuel combustion, non-ferrous metal production and waste incineration, have been suggested to contribute significantly to the mercury contamination (Ochoa-acuna

The aim of the study was to investigate species composition of the small mammal community of the Romincka Forest (NE Poland) with the aid of the tawny owl Strix aluco as a material collector and to estimate the efficiency of the methods applied. In total, 1209 small mammals were sampled, 909 of which were classified as belonging to one of the 15 species identified. Using the rarefaction method we assessed that in order to record 95% of all the mammal species present, 434 individuals randomly selected from the whole material need to be sampled (i.e. 47.7%). The estimation of the total species richness indicated that all species inhabiting the forest under study were recorded. For two less common mammals, the common pine vole Microtus subterraneus and the common dormouse Muscardinus avellanarius, we made an attempt to calculate the number of animals annually killed by the tawny owl population. Our calculations were based on the proportion of small animals in owls’ diet and the density of these birds of prey...

Differences in the frequency with which bats feature in the diet of tawny owls Strix aluco were studied, as these relate to types of habitat occupied (i.e. urban park, suburban forest, non‐urban land outside forest, and non‐urban forest as divided into forest edge or forest interior). The pellets collected at 152 sites in central and north‐eastern Poland in the years 1990–2008 comprised 17,908 items of vertebrate prey, of which 115 (0.64%) were bats. Tawny owls caught 11 bat species, most frequently Nyctalus noctula, Plecotus auritus and Eptesicus serotinus. The analysis revealed habitat‐related differences to the proportions of all tawny owl prey items accounted for by bats, being the highest in urban habitats (2.0%) and suburban forests (0.8%), and the lowest in forest interiors (0.1%). Bat frequency in the diet of tawny owls correlated negatively with that of other mammals pooled together with amphibians. Myotis nattereri and “aerial hawkers” (vs. “gleaners”) were taken significantly more often in habi...

Capsule The annual average breeding frequency, clutch size, offspring production and chick survival of Tawny Owls did not differ between rural and urban nesting territories. Aims To determine whether the general intensity of human habitation in the territory affects breeding. Methods Clutch size, offspring production, breeding frequency and prey abundance were determined from 210 rural and 60 urban nesting territories monitored between 1994 and 2006. Results Fluctuations in the annual average clutch size did not differ between habitats. Clutch size and offspring production paralleled each other in rural habitats but not in urban ones. Annual average clutch size followed the regional spring abundance of small mammals in rural Tawny Owls but not in urban ones. The breeding frequency was higher after mild winters in rural environments but not in urban ones. Conclusion Over an extended time period, rural and urban habitats were largely of equal quality. In urban environments, however, owls seem to be less aff...

The diet of the Tawny Owl (Strix aluco) from five administrative districts in Lithuania was studied in the breeding seasons of 1999–2005. A total of 67 samples with 3,211 prey items were analysed. The common dormouse (Muscardinus avellanarius) comprised 2.0% by numbers and 1.4% by biomass consumed. The difference between districts was 2.3-fold and 2.6-fold, accordingly. It is obvious that this species is not a primary prey, but 15 species of mammals and 30 bird species were represented by numbers not exceeding that of M. avellanarius. Thus, we do not consider M. avellanarius among the rarest prey items. Moreover, in Lithuania, especially in the central part (Kėdainiai district), the share of M. avellanarius in the diet of S. aluco is one of the highest in Europe.

In 1989–1991, the feeding ecology of Tawny Owl (Strix aluco) was studied in Wigry National Park (NE Poland). Diet composition was investigated by analysis of pellets gathered in stands under roost trees or nest boxes from April to August in 3-5 home ranges each year. In order to assess potential prey, small animals were caught in 28 traps. Small mammals composed 66.5% of prey items and 78.9% of food biomass of Tawny Owl, birds - 8.1% and 13.9%, and frogs - 17.4% and 6.8% of prey and biomass, respectively. The diet was dominated by rodents, mainly bank vole (Clethrionomys glareolus) and common vole (Microtus arvalis), which together composed 37.0% of prey items and 37.2% of the biomass consumed. Among birds, the most common prey was Song Thrush (Turdus philomelos). Slightly preferred prey were field mouse (Apodemus agrarius), short-tailed vole (Microtus agrestis) and bank vole. One pellet contained 1-11 (mean 2.34 ± 0.09) prey items. Amphibians were the most numerous during May and June.

Capsule: In the areas studied, Tawny Owls showed extreme flexibility and opportunism, occupying most available vegetation types and elevations below the tree-line. Aims: To assess habitat relationships for the species so as to forecast the potential impact of habitat changes. Methods: We censused a total of 321 territories in 12 study areas covering the regional variation in elevation and the associated heterogeneity in vegetation types and landscape configurations. Results: The species occupied virtually all vegetation types and landscape configurations below the tree-line. Nests were mostly located on cliffs, but also in tree cavities, buildings, and stick nests of other raptors. Density varied from 12 to 60 territories/100 km2 and mean nearest-neighbour distance from 0.7 to 1.8 km, depending on the availability of broadleaved woodland. Compared to availability, nests were nearer to cliffs and had higher richness of habitat edges and vegetation types, which positively affected chick production. Diet composition varied widely according to habitat and was mostly dominated by Edible Dormouse Glis glis, voles and mice. Conclusion: The conservation status of the species was satisfactory. Future habitat changes may favour an increase in density. Silvicultural practices encouraging more old trees with large cavities would further favour this opportunistic species. © 2006 British Trust for Ornithology.

Data for 1997–2005 on the Tawny Owl (Strix aluco) diet during the breeding period (food remains from nest-boxes after breeding) were compared with long-term (spring and autumn 1997–2004) data on small mammal monitoring and short-term trapping data obtained close to owl nest-boxes (autumn 1999 and 2000). The investigated sites were located in the Kėdainiai district (central Lithuania). A total of 18 mammal species were identified in the diet (91.3% of 2,042 identified remains). In general, mammal diversity in the diet was much higher (9 to 15 species recovered annually) than in trapping. Owls mainly preyed on bank voles (31.0% of all recovered mammals), short-tailed voles (15.8%, Microtus in total – 29.5%) and yellow-necked mice (14.6%). At the monitoring site, 969 individuals of 12 species (5 to 10 species annually) were trapped. Dominant was the bank vole (47.6%), followed by the yellow-necked mouse (18.7%) and common vole (14.1%, Microtus in total – 16.4%). A total of 193 individuals of 9 small mammal s...

Diet composition and food niches of two common and widespread in Lithuania owl species, Tawny Owl (Strix aluco) and Long-eared Owl (Asio otus), were analysed from irregularly collected pellets. S. aluco was characterised by a more diverse diet and a wider food niche: 14 small mammal (93.1% of the recovered items) and two amphibian (5.2%) species, a few passerine birds (1.1%) and representatives of three Coleoptera groups (0.6%) were recovered, whereas for A. otus – nine small mammal and two Carabidea species. By numbers, primary food resources of S. aluco were C. glareolus (31.4%), M. arvalis (27.9%) and A. flavicollis (14.3%), whereas of A. otus - M. arvalis (70.8%), all Microtus voles constituting 95.2%. Diet diversity of S. aluco was more than twofold higher (Shannon’s H = 2.62 vs. 1.16). According to biomass, main foods consumed by S. aluco were C. glareolus, M. arvalis and A. flavicollis (27.6, 25.0 and 22.4%, respectively). For A. otus, Microtus voles represented 95.8% of biomass consumed (M. arvali...

The aim of this work was to investigate the diet of the Tawny Owl (Strix aluco) in NE Poland. Pellets were collected in the territory of one owl in the centre of the Romincka Forest twice a year, in spring and autumn, from 2000 to 2003. Among 450 identified prey items, rodents (38% of prey items), amphibians (34%) and insectivores (17%) constituted dominant groups. Birds were caught only occasionally (5%). Significant differences were found in the diet composition between the two seasons. Birds and insectivores were hunted more frequently in winter and spring, whereas the proportion of murid rodents and amphibians in the diet was higher in the summer-autumn period. The percentages of microtines found in the pellets were comparable between the two seasons. Amphibians preyed on in winter and spring had thicker femurs than those caught in summer and autumn.

Data on the Tawny Owl diet from the prey remains found in nestboxes after a breeding period in 1997–2004 in Kėdainiai district and in 1999–2003 in the Kamanos State Strict Nature Reserve are compared with the results of small mammal monitoring in these territories. The number of small mammal species found in the owl prey remains as well as their diversity was always greater, than that obtained by trapping. On average, 12.1 ± 0.9 species were recovered from prey remains in Kėdainiai, 11.3 ± 1.9. in Kamanos State Strict Nature Reserve, while the number of species trapped was 7.0 ± 0.6 and 6.8 ± 1.7 accordingly. Shannon.s H in prey remains was 2.62 ± 0.11 and 2.80 ± 0.14 vs. 1.97 ± 0.13 and 1.65 ± 0.33. It is obvious, that quite a lot of small mammals that are seldom trapped are found in owl prey. Analysis of prey remains may be used as a method for small mammal monitoring.

The paper presents the material on the Tawny Owl (Strix aluco) diet collected during the breeding period (April–May) in Sakiai district. Prey remains from 11 nestboxes occupied by owls in 1986–1987 and 1997–2004 were analysed. The remains of 15 small mammal species, 18 bird species, two amphibian species and two genera of insects were recovered. The dominating small mammal species (n = 361) were Clethrionomys glareolus (24.6%), Microtus arvalis (20.5%), Apodemus flavicollis (11.6%), Microtus agrestis (8.8%) and Sorex araneus (8.6%). Among birds, the most often preyed were Turdus philomelos, T. merula, Fringilla coelebs and Coccothraustes coccothraustes. Frogs Rana arvalis and R. temporaria as well as insects Dytiscus sp. and Melolontha sp. were also present in the food remains. The species composition and the number of small mammals preyed in Sakiai district were compared to the respective data from Kėdainiai district, Kurtuvėnai Regional Park and Kamanos Strict Nature Reserve. The diet of the Tawny Owl i...

Capsule Jays Garrulus glandarius are the most common predators, but carnivorous mammals and some other species also predate nests. Aim To uncover the mechanisms and consequences of nest predation. Methods I used video-recording equipment to record the fates of 132 nests of Blackcap Sylvia atricapilla over a three-year period. An additional 69 nests without video-recording equipment were monitored for comparison. Results I found a total of 11 species depredating eggs and young of Blackcap. The main predator was Jay, which hunted during the day and was responsible for 21% of nest fates and 46% of nest losses. Many other predators were recorded, mainly carnivorous mammals (Stone Marten Martes foina, Red Fox Vulpes vulpes, Least Weasel Mustela nivalis), which hunted from dusk until dawn and accounted for 25% of nest losses. Wild Boar Sus scrofa and Tawny Owl Strix aluco also predated nests. Whereas mammals needed up to 15 minutes at a nest to consume nest contents, Jays stayed only a few seconds to remove egg...

We compared estimates of annual survival rates of tawny owls ( Strix aluco ) ringed in southern Finland from several different sampling methods: recoveries of birds ringed as young; recaptures of birds ringed as young; recoveries of birds ringed as adults as well as young; combined recoveries and recaptures of birds ringed as young, and combined recoveries and recaptures of birds ringed as adults and young. From 1979 to 1998, 18 040 young owls were ringed, of which 983 were recaptured as breeders in subsequent years during this period, and 1764 were recovered dead at various locations. In addition, 1751 owls were ringed as adults, of which 612 were later recaptured and 199 were recovered dead. First-year survival rates estimated using only recoveries of birds ringed as young averaged 48%, while apparent survival rates estimated using only recaptures from birds ringed as young averaged 10-13%. Use of combined recapture-recovery models, or supplementary information from recoveries of birds ringed as adults,...

Feeding of tawny owl, Strix aluco, was studied from 14 localities of northern and central Italy, where it preyed mainly upon mammals and birds, but amphibians and invertebrates were also frequently eaten. Predation upon mammals was more important from autumn to spring, when alternative prey (amphibians, birds and invertebrates) were less available. The food niche overlaps, the linear distances (in km) between the various localities were negatively correlated, and the mean size of prey taken increased with the proportion of forested territory. However, where tawny owl preyed upon large forest mammals, it also preyed upon larger mammals not typical of forests. Considering the relationships between forest structure and tawny owl diet, it was found that forest density was positively correlated with the proportion of arvicolids and negatively with prey size diversity and the proportion of myoxids. The amount of forest territory within 1 km radius from each pellet collection site largely explained diet...

Two groups of eight long‐eared owls, Asio otus, and eight tawny owls, Strix aluco, which entered a Rehabilitation Centre as nestlings, were studied. When more than 60 days old they were released to the wild. The aim of this study concerns the analysis of their behaviour immediately after release and their adaptation to natural life. The owls were radio‐tagged and followed continuously, also with direct observation, until they disappeared from the area or died. The long‐eared owls, released in an agricultural area with scattered woods, were reluctant to fly frequently and remained mostly in thick vegetation along stream banks or very close to the release pen itself. Nevertheless, they progressively enlarged their home range in a matter of days. Half of them disappeared from the study area within 11 days; three others died in a few days, apparently from starvation, while the last owl was rescued because it fell into a stream. In contrast, the tawny owls had a much better survival rate, as only one ...

Capsule The method reliably accounted for variation in brood size when used by a ‘naive’ observer.

We studied the geographical variation of song in tawny owls, comparing temporal and frequency measures of the ≪hoot≫ in two races of the species (English and Italian) and in both adjacent and distant populations within each race. We found the two races differed significantly in five of the 13 parameters considered, duration of the second note, lowest frequency of the first note, and frequency modulation amplitude being the most important variables; Italian and English hoots were discriminated with a high success rate (86.7%). The seven populations also differed significantly from each other, particularly in the lowest frequency, but the overall rate of correct classification was lower (78.2%). Microgeographic variations between adjacent populations occurred in both countries: in general, the frequency measures varied through populations according to the habitat, being higher in open farmland and lower in dense woodland or urban habitats. A mosaic pattern of culturally transmitted hoot variations ...

Tawny Owls respond well to imitation or playback of conspecific calls. In 94% of known territories a response to imitation was obtained within 30 min. No measured temporal or weather variable had any effect on response time. The only factor that appeared to influence response time was population density, with birds in open farmland responding faster and more vigorously than those in continuous woodland. This is considered to be due to lack of exposure to other owls in open farmland. Female owls respond more to imitated male calls in autumn than in winter and spring. This may be due to the fact that autumn is when pair formation occurs, and females may be investigating new males. Alternatively they may be defending their territory at a time when juveniles are searching for vacancies. The findings suggest that censusing should be conducted for 30 min, at any time throughout the winter and in any reasonable weather conditions.

Faced with the problem of mapping accurately the Tawny owl's territories, we used spectrographic analyses of the recorded territorial calls to distinguish the different individual males. From November 1986 to August 1988 we collected about 2000 hootings from different Tawny owls. The visual analysis of the spectrograms revealed a high degree of inter-individual variation and a certain amount of intra-individual variation in the song, so that we have submitted a sample of 140 calls of 17 identified individuals to univariate and multivariate analyses, in order to reach objective conclusions. Seven temporal parameters of the song were selected and measured. The coefficient of variation for each parameter and the test of homogeneity of variances between two series of calls of the same owl showed a stability over time of the selected parameters. On the other hand, the ANOVA test indicated that all the parameters of song varied significantly within the population and discriminant analysis provided a correct cla...

From October 1986 through September 1989, the diet of tawny owls Strix aluco in the city of Pavia (northern Italy) was studied by examining 769 pellets coming from 4 pellet‐dropping stations. The results show that the owls fed mainly on birds (61.1% in biomass), whereas mammals accounted for 37%. Arthropods, especially ants, were numerous in the diet, mainly during summer although their biomass was slight. Seasonal changes in diet occurred throughout the year. During winter, the owls preyed on birds and mammals in the same proportions. Birds largely predominated in spring and sum mer, while mammals slightly prevailed in autumn. The diet of dif ferent individual tawny owls was quite similar qualitatively, but dif fered quantitatively, according to the habitats included in their respective territories.

Two small mammal species only, a shrew and a dormouse, are identified as prey of the Tawny Owl /Strix aluco) in NW Turkey. The shrew Sorex caucasicus can be identified by the dimensions of its mandibles. The taxonomy of the dormouse Glis glis orientalis is discussed, and it is confirmed that it is the only subspecies in N Turkey.

The play‐back method and individual recognition of males were used to study the distribution, habitat and home range characteristics of a population of tawny owls, Strix alucc, in the city of Pavia (Northern Italy) from October 1986 until September 1988. The study area (2000 ha) included the city centre, residential areas and suburbs; in the first breeding season 19 territories were mapped and 22 in the following season, for a mean density of 0.9 and 1.1 Am2, respectively. The favourite habitats in the sub‐urban territories were the natural vegetation, poplar groves and rows of trees, versus monuments, avenues and old built‐up areas in the inner zones.