Ural Owl Strix Uralensis Research Articles

First Record of Ural Owl Strix uralensis Nesting on a Steel Tower

Ural Owls Strix uralensis often use nest boxes, but there have been few reports of them using other man-made structures. We discovered a Ural Owl nest on a steel tower in a suburban area in Ibaraki Prefecture, central Japan, in May 2019. The nest had been built in a jointed part of the steel frame that supported the body of the tower, which was approximately 10 m-high. In this case, a neighboring shelterbelt seemed to provide the owls with leaf litter for the nest floor and hiding places for the parents and their fledglings.

Differential responses of coexisting owls to annual small mammal population fluctuations in temperate mixed forest

Montane temperate forests in central and southern Europe host diverse small mammal assemblages, but the fluctuations in these assemblages in correlation with owl predators are still poorly explored. The key questions of our study were how coexisting owls responded to different prey fluctuations and whether any particular small mammal species governed predator–prey co‐dynamics. We conducted a long‐term study (2004–2020) in low‐elevation (300–1100 m above sea level) mixed Beech and Silver Fir forest in the northern Dinaric Alps (central Slovenia). Monitoring data on the main small mammal groups – mice Muridae, voles Cricetidae, dormice Gliridae and shrews Soricidae – and three owl species – the Ural Owl Strix uralensis, Tawny Owl Strix aluco and Boreal Owl Aegolius funereus – were collected annually. To find relationships between prey and predator populations, we used two types of supervised machine learning approaches and addressed three predictive modelling tasks of multi‐target regression. The dominant species in the small mammal assemblage, the Yellow‐necked Mouse Apodemus flavicollis, had a key role in determining predator populations and their breeding performance. We noted higher sensitivity to small mammal fluctuations in boreal zone owl species (Boreal Owl and Ural Owl), which reach their southern distribution limit in the Dinaric Alps, whereas the temperate zone species (Tawny Owl) seemed to be less affected. In years of prey shortage, the Boreal Owl was found to presumably abandon its territories, the Ural Owl suppressed breeding and the Tawny Owl sustained breeding activity by shifting prey selection. Low‐elevation forests appeared to be suboptimal habitat for the competitive subordinate Boreal Owl, which may exploit occasional outbreaks of small mammal populations in these habitats even in the presence of larger competitors. Whether low‐elevation forests can play a role in maintaining threatened and cold‐adapted Boreal Owl populations in central and southern Europe in the face of recent ecosystem changes due to climate and environmental changes remains an open scientific question.

The co-occurrence of Ural Owls Strix uralensis and Northern Goshawks Accipiter gentilis differs between extensive and fragmented forests

ABSTRACT Capsule Territories of the nocturnal Ural Owl Strix uralensis and diurnal Northern Goshawk Accipiter gentilis were spatially associated in fragmented forest but not in extensive forest. Aims To test the hypotheses that (i) the patterns of distribution of Ural Owl and Northern Goshawk territories are different in extensive and fragmented forests and (ii) the distribution of their territories do not depend on local forest structure and habitat variables. Methods The territories of Northern Goshawks and Ural Owls were identified in forests in southern Poland. Spatial analysis was used to examine the co-occurrence patterns of the two species, and multivariate analysis to examine the impact of environmental cues on territory selection. Results Most habitat parameters were not significantly related to the presence of territories of either species. For Northern Goshawk there was a positive association with the occurrence of old-growth patches and a negative association with clear-cut areas and proximity to forest edge in fragmented forests; for Ural Owl there was a significant effect of wood type in extensive forest. None of the habitat parameters distinguished the territories of the two species, suggesting similarity in the habitats used. The territories of the two species were spatially associated in fragmented forests, suggesting some positive interspecific relationship. In contrast, the distributions of the two species were not significantly associated in extensive forest. Conclusions To explain the spatial co-occurrence between Northern Goshawks and Ural Owls we suggest: (i) Ural Owls can occupy unused Northern Goshawk nests in managed extensive forest where there is a deficiency of large tree cavities; (ii) restricted availability of habitat in fragmented forests forces both species to nest in close proximity, and/or (iii) Ural Owls use social information from Northern Goshawks about habitat quality when selecting territories in some landscapes.

Helminth fauna of birds of prey (Strigiformes: Strigidae, Tytonidae) in the Non-Black Earth Region of the Russian Federation

The purpose of the research is studying helminths of carnivorous birds of the order of owls (Strigiformes) found in the Non-Black Earth Region of the Russian Federation.Materials and methods. From 2015 to 2020, complete helminthological dissections were carried out by the Skryabin method for 72 birds of the order of owls after their spontaneous death: 8 specimens of the short-eared owl Asio flammeus, 6 specimens of the Ural owl Strix uralensis, 4 specimens of the little owl Athene noctua, 9 specimens of the barn owl Tyto alba, 19 specimens of the tawny owl S. aluco, and 26 specimens of the long-eared owl A. otus. The study material was provided by rehabilitation centers and veterinary clinics in Moscow City and the Moscow, Tula and Kaluga regions. The helminths were fixed according to generally accepted methods; the species was identified taking into account specific morphological characters.Results and discussion. Total infection rate in owls was 89.9%. All studied birds were found to have mixed infections with two or more types of helminths. We identified 15 helminth species including 3 species of trematodes (Neodiplostomum attenuatum, Strigea falconis, S. strigis), 2 species of cestodes (Cladotaenia globifera, Paruterina candelabraria), 9 species of nematodes (Syngamus trachea, Cyrnea leptoptera, Microtetrameres inermis, Synhimantus laticeps, Porrocaecum depressum, P. spirale, Capillaria tenuissima, Baruscapillaria falconis, and Capillaria sp.) and 1 acanthocephalian species (Centrorhynchus aluconis). For the first time, new hosts were identified for the following helminth species: the barn owl, short-eared owl and little owl for the trematode N. attenuatum, the Ural owl and little owl for S. falconis, the long-eared owl for the nematode S. trachea, the short-eared owl and tawny owl for C. leptoptera, and the tawny owl for M. inermis.

Differences in the niches of keratin/chitin feeding moths (Lepidoptera: Tineidae) in bird nests in central Japan

Some moth larvae feed not on plants but on keratin and/or chitin produced by animals. These substances are polymers and are commonly found in bird nests as feathers and raptor pellets. Many qualitative studies have examined the association of keratin/chitin feeding moths with bird nests. However, few studies have quantified the species composition with respect to type of nest and habitat. Hence, we have studied the degree to which the niches of these moths differ in terms of type of nest and habitat. We set-up open-top nest boxes for the Ural owl Strix uralensis (damp exposed nests from which owl chicks were fledged successfully) and artificial bird nests (mesh bags filled with duck down to imitate dry exposed nests) in a deciduous forest and artificial bird nests in an urban setting in Aichi Prefecture, central Japan, and collected the contents of the nests every two months from June to December 2014. We recorded 592 individuals of five keratin/chitin feeding moth species (Tineidae, Tineinae) from the contents. Using non-metric multidimensional scaling and cluster analysis of the relative abundances of individual species in each type of nest in forest and urban settings, these species were classified into three groups: (1) Monopis longella and M. congestella inhabiting forest, (2) M. flavidorsalis and Niditinea tugurialis mainly in damp exposed nests in forest and (3) N. piercella mainly in dry exposed nests in urban areas. This classification was compared with findings of other studies. As a result, these moths probably have different niches with respect to nest type (damp or dry), keratin/chitin as a source of food (raptor pellets or feathers), and habitat (forest or urban area). Furthermore, we suggest that the evolution of larviparity in M. congestella might be related to its preference for feathers as a source of food for the development of its larvae.

Effectiveness of vole control by owls in apple orchards

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

A comparative study of Ural Owl Strix uralensis breeding season diet within its European breeding range, derived from nest box monitoring schemes

ABSTRACTCapsule: Voles are the main prey of the Ural Owl Strix uralensis in Europe, with larger prey and higher prey diversity being positively associated with owl breeding performance.Aims: To assess the breeding diet and its influence on the breeding performance of the Ural Owl across a north–south gradient of its European range using nest box monitoring data.Methods: Comparable monitoring of nest boxes in different biogeographical regions of Europe (Finland, Latvia, Slovenia) and diet analysis from nest samples to assess the taxonomic and trait influence of prey on owl breeding performance in different environments.Results: High plasticity in the Ural Owl hunting behaviour under different prey availability conditions resulted in significant differences between regions and years. Voles formed the highest proportion of the diet in all studied regions. Owl brood size was positively associated by higher proportions of voles and mice in the diet, and with increasing proportions of seasonally available larger prey and consequently prey diversity. Brood size was negatively associated with the proportion of non-mammalian and predominantly forest-living prey.Conclusions: The study highlighted the importance of comparative studies of raptor ecology across their geographical ranges in different environmental conditions to reveal undiscovered patterns, which may go undetected when conducting studies at the regional scale only.

Towards integrated population monitoring based on the fieldwork of volunteer ringers: productivity, survival and population change of Tawny Owls Strix aluco and Ural Owls Strix uralensis in Finland

ABSTRACTCapsule: Monitoring of demographic parameters by volunteer ringers provides insight into the factors driving population changes in owls.Aims: To assess the value of national ringing, recapture and recovery data from volunteers to understand population dynamics.Methods: We analysed 49 years of ringing, recapture and recovery data from throughout Finland for Tawny Owls Strix aluco and Ural Owls Strix uralensis and compared them with annual population and productivity indices from other volunteer-based surveys.Results: Volunteer-based ringing data show that all aspects of the demography of Ural and Tawny Owls fluctuate dramatically in relation to an approximately three-year cycle of voles. When voles are abundant, a high proportion of owls breed and many young are produced; however, few of those young survive because vole populations crash the following winter. Survival of adults fluctuates less than that of young, suggesting that adults are better able to survive on alternative prey. In 2005, when vole populations remained high two years in row, many young were produced and survived, leading to a peak in owl breeding populations four years later at the top of the next vole cycle. This was immediately followed by a crash in populations suggesting a density-dependent interaction with vole abundance. Changing climate could affect owls both directly, by influencing winter survival, as well as indirectly through impacting prey availability.Conclusion: Encouraging similar, volunteer-based national-scale ringing efforts for owls elsewhere in Europe, especially for Tawny Owls which occur in most countries, would be a cost-effective way to understand how factors such as changing prey availability, climate and habitat availability are influencing the population levels of this and other raptors.

Obročkovalna Dejavnost in Pregled Najdb Obročkanih Ptic V Sloveniji V Letu 2013 / An overview of bird ringing in Slovenia in 2013

Abstract In 2013, 73,529 birds of 161 species were ringed in Slovenia, with 114 finds from abroad, 73 finds of foreign-ringed birds and 1580 local finds. The most numerous ringed species were Blackcap Sylvia atricapilla and Barn Swallow Hirundo rustica, while among ringed nestlings Great Tits Parus major and Blue Tits Cyanistes caeruleus prevailed. The most numerous species among recoveries was the Mute Swan Cygnus olor with probably the oldest swan recorded in Slovenia so far, a 25-year-old female. The longest distance recovery concerned a Sedge Warbler Acrocephalus schoenobaenus from Norway (2,801 km). Of interest among local finds is the longest recovery distance (122 km) recorded for Ural Owl Strix uralensis in Slovenia so far. In 2013, two rare species for Slovenia were ringed, Yellow-browed Warbler Phylloscopus inornatus (2 individuals) and Siberian Rubythroat Calliope calliope, which was the first record for Slovenia. The first analysis of ringing sites in Slovenia is given as a baseline for establishing a network of Constant Effort Sites

Raptors as surrogates of biodiversity along a landscape gradient

Summary With biodiversity facing threats, there is a need to improve reserve selection procedures. However, detailed information about different biodiversity measures (e.g. species richness) at potential sites is often lacking, and selecting areas that protect most biodiversity is difficult. To simplify matters, biodiversity surrogate species, that is, species associated with higher biodiversity than average, have been used for area selection. However, consensus about the performance of the surrogate species concept is lacking, and there are few studies investigating potential differences in the effectiveness of multiple predators as surrogates for biodiversity over large spatial scales. We evaluated two avian predators, the northern goshawk Accipiter gentilis and the Ural owl Strix uralensis, as surrogates for biodiversity in the boreal forest biome in Western Finland. We used a study design including nest sites and two reference sites for each nest, the diversity of birds and wood‐decaying fungi (polypores). We assessed simultaneously whether surrogacy persisted at the landscape level while moving from one vegetation zone to another. We generally found more birds and polypores around the nest sites for both goshawks and Ural owls than at their respective reference sites. However, the goshawk outperformed the Ural owl. Additionally, although biodiversity was found to decrease at the landscape scale as a result of a decrease in vegetation complexity with increasing longitude, the surrogacy efficiency of the raptors remained unchanged. Synthesis and applications. These findings suggest that the surrogate species concept applied to raptors may be an efficient addition to methods for identifying areas of conservation priority, even across vegetation zones. We conclude that protecting areas around raptor nests is a method to consider in order to halt forest biodiversity loss. Finally, sampling biodiversity along diversity and landscape gradients can improve the necessary assessment of surrogate species.

Diet of the ural owl (Strix uralensis) in Slovakia

Abstract A Central European subspecies of the Ural owl Strix uralensis macroura (Wolf, 1810) is widespread in the territory of Slovakia. The work presents unpublished data on the diet of this subspecies from several territorial units of eastern and northern Slovakia, obtained from pellets and the nest linings in boxes (1 ,564 pieces). There is less data about prey brought to young in the nest but still not yet consumed (137 pieces). Published data from analysis of the stomachs of dead and shot owls come from the first six decades of the 20th century. Together with existing published data, 2,134 pieces of the diet of S. uralensis from Slovakia are evaluated. They indicate the dominance of non-forest species Microtus arvalis and a more plentiful representation of larger species of prey: Lepus europaeus, Sciurus vulgaris and Corvus sp. In upper Orava the diet of young S. uralensis also consists of frogs Rana temporaria, moles Talpa europaea and mountain species of rodents: Microtus agrestis, M. subterraneus, Sicista betulina and Arvicola amphibius. In data from the mountains of central Slovakia the Clethrionomys glareolus has high abundance, and in eastern Slovakia the Apodemus flavicollis and A. agrarius are more represented, and in the lowlands also the Cricetus cricetus. Upon evaluation ofmaterial from the entire breeding grounds of S. uralensis it can be deduced that the basic diet consist of mammals (88.6%) from the orders Soricomorpha and Rodentia. In the countries of Central Europe the species M. arvalis, M. subterraneus, A. flavicollis and Muscardinus avellanarius are more abundantly represented, and in the Baltic states the species Sorex araneus, M. agrestis, M. oeconomus and M. rossiaemeridionalis. The species S. betulina and A. agrarius occur in the diet of S. uralensis from Central Europe up through the Far East.

Potential resource competition between an invasive mammal and native birds: overlap in tree cavity preferences of feral raccoons and Ural owls

Invasive mammals include good tree climbers that use tree cavities for resting and nesting. Tree cavities are important but limited resources in most forests; thus, some invasive mammals can be serious competitors for native cavity-using species, especially cavity-nesting birds. Despite the potential impact, such inter-class competition has rarely been considered. We examined the possibility of resource competition for tree cavities between the invasive raccoon Procyon lotor and the native Ural owl Strix uralensis. Both species are nocturnal and use tree cavities during daytime. We assessed an overlap in cavity use for both species as an indication of potential competition by monitoring 341 cavities during their breeding season in a natural park in Hokkaido, Japan. Of 341 potentially available cavities, raccoons and Ural owls used 37 and 32, respectively. The characteristics of 58 cavities used by raccoons or owls were compared to 49 random cavities to determine if they selected cavities with certain characteristics. As predicted from a large amount of tree cavities and a low raccoon density in this managed forest, we did not find direct evidence of competition, such as physical interaction, intrusion to cavities, or habitat segregation. Cavity types used by both species overlapped considerably in terms of height, entrance size, depth, and other characteristics: their habitats were widely overlapped. Further, in four cavities, one species was replaced by the other. Given the similar habitat requirements, the invasive raccoon could be a potential competitor for Ural owl when raccoon density increases and/or cavity availability decreases, which is the case for many forests in Japan. This study suggests that potential threats of resource competition among not only closely but also distantly related taxa should be taken into consideration when studying the impacts of invasive species.

Food Habits of the Ural Owl (Strix uralensis) During the Breeding Season in Central Japan

Abstract We studied the diet of Ural Owls (Strix uralensis) living in the forests of Mt. Yatsugatake, central Japan, in the context of historic logging activities that have greatly extended the amount of open pasture and consequently modified small mammal availability in the region. We used owl pellets from artificial nest boxes to quantitatively analyze diet composition during the breeding season. We identified 1026 small mammals from 17 owl nests. Mandibles were identified and categorized as wood mice (Apodemus spp.), voles (Microtus sp.), and shrew-moles (Urotrichus talpoides). The small-mammal component of the diet was dominated by wood mice (71%), followed by voles (24%) and shrew-moles (5%). This contrasts sharply with the vole-dominated diets associated with most European Ural Owl populations. We also detected significantly fewer voles among mammalian remains for nests at greater distances from open-pasture habitat. We confirmed previous results from studies of Ural Owls in Japan that suggest elast...

Selection on plasticity of seasonal life‐history traits using random regression mixed model analysis

Theory considers the covariation of seasonal life-history traits as an optimal reaction norm, implying that deviating from this reaction norm reduces fitness. However, the estimation of reaction-norm properties (i.e., elevation, linear slope, and higher order slope terms) and the selection on these is statistically challenging. We here advocate the use of random regression mixed models to estimate reaction-norm properties and the use of bivariate random regression to estimate selection on these properties within a single model. We illustrate the approach by random regression mixed models on 1115 observations of clutch sizes and laying dates of 361 female Ural owl Strix uralensis collected over 31 years to show that (1) there is variation across individuals in the slope of their clutch size–laying date relationship, and that (2) there is selection on the slope of the reaction norm between these two traits. Hence, natural selection potentially drives the negative covariance in clutch size and laying date in this species. The random-regression approach is hampered by inability to estimate nonlinear selection, but avoids a number of disadvantages (stats-on-stats, connecting reaction-norm properties to fitness). The approach is of value in describing and studying selection on behavioral reaction norms (behavioral syndromes) or life-history reaction norms. The approach can also be extended to consider the genetic underpinning of reaction-norm properties.

The impact of climate and cyclic food abundance on the timing of breeding and brood size in four boreal owl species

The ongoing climate change has improved our understanding of how climate affects the reproduction of animals. However, the interaction between food availability and climate on breeding has rarely been examined. While it has been shown that breeding of boreal birds of prey is first and foremost determined by prey abundance, little information exists on how climatic conditions influence this relationship. We studied the joint effects of main prey abundance and ambient weather on timing of breeding and reproductive success of two smaller (pygmy owl Glaucidium passerinum and Tengmalm's owl Aegolius funereus) and two larger (tawny owl Strix aluco and Ural owl Strix uralensis) avian predator species using long-term nation-wide datasets during 1973-2004. We found no temporal trend either in vole abundance or in hatching date and brood size of any studied owl species. In the larger species, increasing late winter or early spring temperature advanced breeding at least as much as did high autumn abundance of prey (voles). Furthermore, increasing snow depth delayed breeding of the largest species (Ural owl), presumably by reducing the availability of voles. Brood size was strongly determined by spring vole abundance in all four owl species. These results show that climate directly affects the breeding performance of vole-eating boreal avian predators much more than previously thought. According to earlier studies, small-sized species should advance their breeding more than larger species in response to increasing temperature. However, we found an opposite pattern, with larger species being more sensitive to temperature. We argue that this pattern is caused by a difference in the breeding tactics of larger mostly capital breeding and smaller mostly income breeding owl species.

Ural owl (Strix uralensis) nesting in floodplain forest in the Východoslovenská rovina Plain

Ural owl (Strix uralensis) nesting in floodplain forest in the Východoslovenská rovina Plain Ural owls started nesting in smaller patches of woodland on the border between the Východoslovenská pahorkatina Upland and the Východoslovenská rovina Plain since 1994. The first data of the presence of Ural owls also in floodplain forest along the Latorica River in eastern Slovakia come from 1926, at first during the winter, and from 1998 also during the nesting period. In 2003 this species was heard in autumn courtship in this area, and on March 31, 2010 the first instance of nesting was noted in woodland to the south of the town Veľké Kapušany in the old nest of a common buzzard (Buteo buteo). This instance of nesting in wetland forest is the first nesting record of this species in this unusual nesting habitat in Slovakia.

Bad News and Good News: Population Changes of Finnish Owls During 1982–2007

In Finland, monitoring of ‘common’ birds of prey is based on two projects run by the Finnish Ringing Centre: the Raptor Grid (since 1982) and Raptor Questionnaire (since 1986). The Raptor Grid has produced sufficient data for analysing population trends in six of ten owl species. The overall trend during 1982–2007 was significantly negative in the Eagle Owl Bubo bubo (-2.2% per year), Long-eared Owl Asio otus (-4.7%) and Tengmalm's Owl Aegolius funereus (-3.1%), and significantly positive in the Ural Owl Strix uralensis ( 1%); no significant trend was detected in the Pygmy Owl Glaucidium passerinum or Tawny Owl Strix aluco. The Eagle Owl population increased to the middle of 1990s, but has since decreased by 5% per year. The decrease coincides with the closing of 90% of local open rubbish dumps, which offered a stable and rich food supply to the Eagle Owls. The decrease in the Tengmalm's Owls can partly be attributed to the decrease in the amount of old forest. The Pygmy Owl population increased steeply (>5% per year) during 1994–2003, then crashed following a mass invasion and has since started to recover. The geographical distribution of the Raptor Grid study plots is not suitable for monitoring the northern nomadic species like the Snowy Owl Bubo scandiacus, Northern Hawk-Owl Surnia ulula, Great Grey Owl Strix nebulosa and Short-eared Owl Asio flammeus. Annual totals of active nests and occupied territories reported with the Raptor Questionnaire do not indicate any long-term population changes of these species. However, intensive cooperation over larger areas across national boundaries in northern Europe is urgently needed for reliable monitoring of these nomadic owls.

Distribution, Density and Habitat Relationships of the Ural OwlStrix uralensis macrourain Croatia

We surveyed the Ural Owl Strix uralensis macroura from 1993 to 2007 to determine the geographic range of the species in Croatia and to provide information on its density and habitat preferences. We conducted playback surveys at 365 survey points within 19 plots (total survey area 1070 km2) systematically covering all of the major forest types in Croatia. Surveys were also carried out at 144 calling stations arranged in transects and at 133 stations scattered over larger areas. Playback surveys were conducted twice at stations in plots and along transects, and once at scattered stations. A total of 234 Ural Owl territories were located. We estimate the total population of the Ural Owl in Croatia to be 700–1000 pairs, and include an updated map of its distribution. The owls occurred in Dinaric fir—beech forests, montane beech, Sessile Oak Quercus petraea and Common Oak Quercus robur forests. The majority of the population, around 80%, was located in Mountain Croatia, where mixed Dinaric fir—beech forests pr...

Ural OwlStrix uralensisPopulation Dynamics and Range Expansion in Western Ukraine

Until the end of the 20th century, the distribution of the Ural Owl Strix uralensis was limited to the Carpathian Mountain area of southwestern Ukraine. The abundance and distribution of Ural Owls in the Ukrainian Roztochchya area was investigated in 2005 and 2007; the density of owls was found to be 1.7–2.0 pairs/10 km2. The species was a very rare vagrant in this area at the beginning of 1990s. The population of the owl has expanded in the past decade and it is now a common species in almost all of western Ukraine. The first indication of a change in the owl population was through an increase in the number of wintering specimens (including those killed on roads). The Ural Owl prefers old beech and rarely uses mixed forests in newly settled forest areas.

Ural OwlsStrix uralensisat the Border Line: Nesting Places are Not a Limiting Factor

The Ural Owl Strix uralensis meets its westernmost distribution in Hedmark County, southeast Norway. Since 1979 we have provided the species with nest boxes in this region. A total of 80 nest boxes were put out in prime Ural Owl habitat, starting with 9 in 1979, 18 in 1982 and 53 in 1985. Two more nest boxes put up by others, and four made by ourselves, were later added, giving a total 86 nest-box localities. The nest boxes were checked up to 2004, when 28 nest boxes were moved to western (n = 8) and central (n = 20) Sweden. We have analysed the results for 25 seasons from 1980 to 2004. For comparison, the results for the 20 nest boxes in central Sweden for the seasons 2005–07 have been included. The Norwegian nest boxes offered a total of 1429 nest-box years. Since all boxes were not inspected each year, the total number of observation-years was 847 (59.3%). Ural Owls only used 4 nest boxes for breeding, occupied for the first time 1, 1, 1 and 10 years respectively after the boxes were put up. The four b...