Asio Otus Research Articles

Changes of nestling ringing dates in nine bird species over seven decades

Climate change co-occurs with an advancement of avian breeding season (indexed as laying dates or fledging dates) in the temperate zone, suggesting a causality between them. Here, we investigate whether the long-term shifts in nestling (chick) ringing dates also mirror this phenomenon. This index is biased by inherent shortcomings, such as the non-independence of dates (in nestmates, colony members), poor accuracy (long period suitable for ringing), and strange shape of distributions. These shortcomings can be reduced by applying the median of annual ringing dates as an index of breeding phenology. The advantage of this index is that data are available for long periods and large sample sizes. By accepting certain compromise between statistical discipline and fieldwork realities, we examined changes in the breeding phenology of 9 bird species from 1951 to 2020 in Hungary. We found that the annual median of ringing dates advanced significantly (by 9–14 days) in the Black-headed Gull, Common Kestrel, Barn Swallow, Great Tit, and Eurasian Blue Tit. Contrarily, no significant (all P > 0.16) changes occurred in the case of the Common Tern, Black-crowned Night-heron, Common Buzzard, and Long-eared Owl. We also found that the proportion of Great Tits’ second brood has been reduced in recent decades.

Lissonema sicki, an emerging air sac nematode of European owls: introduction, host switching and rapid establishment on a Mediterranean island.

In recent years, air sac parasitic helminths have been reported to cause severe disease in birds. In addition, various species appear to be expanding and infecting new avian hosts in various regions worldwide. In this context, an air sac nematode was initially detected in 2014 infecting the Eurasian scops owl, hospitalized in the local wildlife hospital in Mallorca (Balearic Islands, Spain). Years later, the parasite was detected in 2 other owl species. Air sac nematodes had never been reported in the Mallorcan Strigiformes before. A comprehensive molecular and morphological characterization analysis, including scanning electron microscopy, was required for species confirmation. The species was identified as Lissonema sicki, a parasite infrequently reported in South American owls. Since its first introduction to Mallorca, it has dramatically increased in prevalence in hospitalized birds, being highly prevalent in the Eurasian scops owl (41%), in the long-eared owl (11%) and in the barn owl (4%). The introduction pathway of this parasite to Europe remains unknown. This discovery underscores the expanding range and impact of L. sicki, emphasizing the importance of ongoing surveillance and research to comprehend and manage the implications of its emergence in new territories.

New records of Suncus etruscus (Soricidae, Mammalia) and its current status in Bulgaria

We present 17 new records of Suncus etruscus in Bulgaria, and the first finding of the species north of Stara Planina Mountains. The species is recorded in the diet of three owl species - Tyto alba, Asio otus and Athene noctua, and one bird of prey - Aquila heliaca. The bulk of records originated from T. alba, in the rest raptor species it is taken randomly and consists negligible part of their diet. Additionally, five dead shrews were used, which provided hard evidence for the presence of S. etruscus in north Bulgaria. All data on the species distribution in Bulgaria are summarised and the roads for its invasion are discussed. Climate change is considered as an expansion trigger for spreading of the Etruscan shrew.

Trophic diet of the Long-eared owl Asio otus (Linnaeus, 1758) (Aves, Strigidae) in the Daya d'El-Gouffa (Laghouat, Algeria)

This research aims to study the trophic diet ofthe long-eared owl Asiootus and based on the examination of 120 regurgitation pellets of this raptor. These pellets were collected during the period from August to november 2020, near the Dayad'El-Gouffa located in the region of Laghouat. The analysis of the 120 pellets revealed a total of 273 individuals divided into 39 species belonging to four zoological classes. The consumption of small mammals, mainly Rodentia-Gerbillidae, is very common in arid environments. These constitute the basis of the diet of this raptor. Of the four families of rodents consumed, the Gerbillidae family is the most dominant one. It clearly stands out from the other families with a very high rate of 92.5% of the total rodents consumed. The Dipodidae are the least consumed (4.8%). In terms of species, Pachyuromusduprasi is the most dominant species with 31.5%. The values of the Shannon-Weaver index seem to be high. The highest one is recorded in november with 4.2 bits against 3.1 bits recorded in august. The calculated equitability values tend towards one for all four months of the study, so the numbers of the different components of the long-eared owl diet tend to be in balance with one another. This implies that Asiootus behaves as a generalist opportunistic predator.

Correlation between Size and Plumage Color of Migrating Male and Female Long-Eared Owls (Asio otus)

Correlation between Size and Plumage Color of Migrating Male and Female Long-Eared Owls (Asio otus)

Adreno-immunological response to healthcare facility noise during rehabilitation of Tropical Screech Owls

Wild animals, particularly those affected by urban expansion frequently face challenges such as vehicle collisions, and encounters with domestic dogs. Rehabilitation in care facilities usually conducted in ex-situ conditions poses considerable challenges. In rescue centers, these animals are exposed to a new environment characterized by human noise and the presence of multiple species in a confined space. This can potentially trigger stress responses and immunosuppression, further compromising their health. This study aimed to assess the endocrine and immunological parameters of owls (Megascops choliba) under human care for a continuous 49-day period. Twelve adult owls were exposed to audio recordings from a rescue center between days 15 and 35. Fecal samples were collected from each owl every seven days, as well as blood samples from eight of these birds. Fecal samples were analyzed for glucocorticoid metabolites (GCM), while blood samples were used to measure plasma corticosterone levels, bacterial killing ability (BKA), and heterophil-to-lymphocyte ratio (H/L). Our findings revealed that GCM concentration increased during noise exposure regardless of sex, while plasma corticosterone levels remained unchanged. BKA decreased during noise exposure compared to before treatment, but H/L did not differ between time points. These results show that exposure to rescue center noise induces alterations in allostatic mediators in owls, requiring further research to address other physiological changes in individuals that may affect their recovery and maintenance under human care.

Assessing Contamination Profiles in Livers from Road-Killed Owls.

Raptors are recognized as valuable sentinel species for monitoring environmental contaminants owing to their foraging behavior across terrestrial and aquatic food webs and their high trophic position. The present study monitored environmental contaminants in livers from road-killed owls to evaluate differences in the exposure patterns due to factors such as species, age, and sex of individuals. Carcasses of road-killed individuals of eagle owl (Bubo bubo), long-eared owl (Asio otus), little owl (Athene noctua), tawny owl (Strix aluco), and barn owl (Tyto alba) were collected in Alentejo (Portugal). Eighty-one organic contaminants were analyzed, including organochlorine pesticides (OCPs), per- and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), pharmaceuticals, in-use pesticides, and organophosphate esters (OPEs). Overall, 21 contaminants were detected. In all species ∑OCPs were prevalent at concentrations from 3.24 to 4480 ng/g wet weight, followed by perfluorooctane sulfonic acid (PFOS), the only PFASs detected (from 2.88 to 848 ng/g wet wt) and ∑PCBs (1.98-2010 ng/g wet wt); ∑PAHs were ubiquitous but detected at the lowest concentrations (7.35-123 ng/g wet wt). Differences among species were observed according to principal component analysis. Eagle owl and long-eared owl presented the highest levels of ∑OCPs, ∑PCBs, and PFOS, consistent with its higher trophic position, while ∑PAHs prevailed in tawny owl, barn owl, and little owl, related to their frequent use of urban areas for nesting and roadsides for hunting. Adults presented higher concentrations of ∑OCPs and ∑PCBs than juveniles, while no differences were observed for PFOS and ∑PAHs. Pharmaceuticals, in-use pesticides, and OPEs were not detected. Overall, the present study shows specific contamination patterns in five species with similar diet but with differences in habitat preferences. Environ Toxicol Chem 2024;43:821-832. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Screech owls, Super Soakers, and school gardens

Screech owls, Super Soakers, and school gardens

Dynamics оf Nesting Ornithofauna Structure оf Tiraspol City’s Resident Area

43 species of nesting birds were registered of Tiraspol City’s resident area in 1999–2019. The total density was about 1995,7–2361 pairs/km2 . House Sparrow, Rock Dove, Tree Sparrow and Common Swift were the dominants. Crested Lark, Willow Warbler and Wood Warbler disappeared from nesting ornithofauna of resident area. Common Kestrel, Common Woodpigeon, Eurasian Scops-owl, Robin, Blackbird, Song Thrush, Blue Tit and Eurasian Nuthatch for 20 years were appeared. A signifi cant increase in abundance was noted in populations of Rock Dove, Long-eared Owl, Common Swift, Eurasian Golden Oriole, Rook and Tree Sparrow. There was a decrease in the number in the populations of Chiffchaff, Northern Wheatear, Black Redstart, House Sparrow and Chaffi nch. The majority of birds nesting in the resident area belong to the Transpalearctic type of the fauna, to the desert-mountains landscape-genetic faunistic complex, to the sklerophilnai ecological group and phytophagan trophic group.

Habitat Factors Driving Long-Eared Owl (Asio otus) Population Growth and Productivity in the Judea Region

Abstract In Israel, Long-eared Owls (Asio otus) were considered primarily a wintering species with documented sporadic breeding. However, by the turn of the last century, it had become an increasingly numerous breeding species in the northern and central parts of the country. Based on the analysis of nest numbers in the Judea region, we determined that the population increased by at least 22% each year between 2003 and 2008, from 28 known nests in 2003 to 118 in 2008. We believe our study was conducted during the initial years for the Long-eared Owl population expansion in the region. We found that birds nesting in more-urban areas produced fewer offspring per brood than birds in more rural areas. We also found that nestlings from more-urban areas, exposed to artificial light at night, fledged earlier than birds from wild areas. The rapid growth in the numbers of nesting Long-eared Owls in the Judea region was likely due, at least in part, to the species’ adaptation to urban areas.

Small mammals near Janowiec nad Wisłą (middle-eastern Poland) on the basis of prey composition of the tawny owl Strix aluco and long-eared owl Asio otus

At two sites near Janowiec nad Wisłą (middle-eastern Poland) the species composition of a small mammal community in the diet of the tawny owl Strix aluco and long-eared owl Asio otus has been examined. The bones of 128 mammals have been extracted from S. aluco pellets gathered in the years 2014-2015, whereas 401 mammals have been extracted from A. otus pellets collected in the years 2023-2024. Dominant species in the diet of S. aluco (the site bordering woodland) were Clethrionomys glareolus (31.3%), Apodemus agrarius (16.4%) and Apodemus flavicollis (12.5%), while in the case of A. otus (the site bordering open landscape) Microtus arvalis (55.1%) appeared most frequent. Altogether 16 species were recorded representing: Soricomorpha (4), Chiroptera (1), Rodentia (10) and Carnivora (1). Two bats caught as prey belonged to the species of Myotis nattereri, common in this part of Poland. Most interesting species were Crocidura leucodon, whose recorded sites are near its range limit, and Muscardinus avellanarius – the species infrequently recorded in central and eastern Poland.

Performance improvement and noise reduction analysis of multi-blade centrifugal fan imitating long-eared owl wing surface

This research was inspired by the long-eared owl's ability to fly silently. For the first time in this study, a wind turbine blade is designed to mimic the wing surface and the leading edge of the long-eared owl. The commonly used two-dimensional blade profile in previous studies is replaced by a more effective three-dimensional profile. This change leads to improved aerodynamic performance of the multi-blade centrifugal fan and reduced noise levels. The airfoil and leading edge profile parameters of the long-eared owl were extracted and utilized. These parameters were used to develop a fitting formula based on their correlation. This formula facilitated the design and optimization of a bionic blade (B-Blade). The results indicate a 4.1% enhancement in the maximum flow rate compared to the original blade fan, alongside a noise reduction of 1.3 dB(A) under identical static pressure conditions. An examination of the internal flow, noise, and sound source characteristics of both fan types was conducted, elucidating the aerodynamic noise mechanism. Fan noise propagation showed pronounced dipole sound source traits. The sound source area at the B-Blade fan's inlet and the volute tongue was more compact, leading to a decrease in mid-low frequency discrete noise. The sound source intensity was also diminished. The B-Blade fan also ameliorated the flow distribution at the impeller outlet, reducing the unstable interaction between the impeller and volute tongue, thereby effectively diminishing noise.

Investigation of roadkilled Western Barn Owls (Tyto alba) in Csanádi-hát region (SE Hungary)

Abstract The Western Barn Owl (Tyto alba) is a common breeder in Hungary. It is a resident bird of open areas, staying near nesting sites in winter. Its population is strongly influenced by food availability, weather conditions and several anthropogenic activities. One of the most important factors of these in recent decades has been road mortality. In this work, we processed data of roadkilled individuals and field observation records in the Csanádihát region in south-eastern Hungary from the period 1995–2022. In Battonya, we have been recording roadkill individuals since 1995, while observations of Barn Owl individuals from Kevermes have been available since 2005. The species is a regular, but scarce breeder in the area, so both the number of roadkilled individuals and the number of field observations were relatively low. Nevertheless, we had the opportunity to examine how the number of individuals of the species that were killed in the traffic varied over time and within years. According to our data, more birds collided during the winter, and also between July and November. This can be explained mostly by the seasonal lack of food and the fledging time of inexperienced juveniles. The temporal distribution of field observations were different from the dynamics of the roadkills, as the species was mainly observed during the breeding season. The exact population size of the area can be difficultly estimated, as it breeds mainly in attics of stable, granary and church buildings. The breeding population of Kevermes was estimated at 3–4 pairs and did not change significantly in the studied period. Over the same 28-year period, using the same methods to the two other most common nesting owl species of the region, we found that the within-year roadkill dynamics of the Little Owl (Athene noctua) and the Northern Long-eared Owl (Asio otus) differed from that of the Western Barn Owls, which may be due to the different feeding habits of the species. We can conclude that the number of roadkilled birds was proportional to the local population of the species.

The Probability of Nesting Success of the Long-Eared Owl (Asio otus, Strigidae, Strigiformes, Aves) Is Determined by the Structure and Heterogeneity of the Breeding Habitat

The Probability of Nesting Success of the Long-Eared Owl (Asio otus, Strigidae, Strigiformes, Aves) Is Determined by the Structure and Heterogeneity of the Breeding Habitat

Variability in methylmercury exposure across migratory terrestrial bird species: Influencing factors, biomagnification and potential risks

Despite China's considerable mercury (Hg) emissions, monitoring of methylmercury (MeHg) levels in its terrestrial environments remains limited. This study examined the occurrence and accumulation of MeHg in body feathers of 12 migratory terrestrial bird species originating from Siberia and northeastern China. Considerable variations in foraging habits and MeHg levels were observed among these species. Accipiters, including Eurasian and Japanese sparrowhawks (A. gularis and A. nisus) and northern goshawk (A. gentilis), along with insectivorous songbirds including grey-backed thrush (T. hortulorum) and orange-flanked bluetail (T. cyanurus), showed notable levels of MeHg (0.62–1.20 mg/kg). Up to 25 % of the individuals within these species were classified as low-risk based on feather Hg toxicity thresholds, while the remaining species fell into the no-risk category. Despite showing enriched δ15N, MeHg concentrations in short-eared and long-eared owls (A. flammeus and A. otus) were lower than in sparrowhawks. The herbivorous oriental turtle dove (S. orientalis) exhibited significantly lower MeHg levels compared to all other species. There was a significant positive correlation between MeHg concentrations and δ15N across species, highlighting the substantial biomagnification potential of MeHg within the terrestrial food web. Additionally, we found significantly higher MeHg levels in adults than juveniles in both sparrowhawk species. Our results demonstrate the effectiveness of utilizing migratory bird feathers for monitoring terrestrial Hg contamination, and underscore the importance of further assessment.

Validation of enzyme immunoassays for quantifying sex steroid hormones in tropical screech owls (Megascops choliba)

Androgens and estrogens are steroid hormones that regulate reproductive processes in both males and females. Monitoring plasma levels of these steroids or their metabolites present in feces, offers diagnostic support for assessing the reproductive status of animals. Immunoassays are commonly used methods for quantifying these hormones, but their protocols require species-specific validation to ensure reliability. The objective of this study was to perform analytically and biologically validation of enzyme immunoassay (EIA) kits for measuring testosterone (T), estradiol (E2), faecal androgen metabolites (fAM), and faecal estrogenic metabolites (fEM) in the tropical screech owl (Megascops choliba). Serum and fecal samples were collected from six adult females and six males both before and during breeding season, with males' gonadal activity assessed using electroejaculation (EE). The parallelism test confirmed the immunogenic similarity of the antigens in the estradiol and testosterone standards and the antigens in the serum samples and fecal extracts of M. choliba. Additionally, the EIA kits displayed nearly 100% recovery rates, and showed coefficients of variation ranging from 8% to 14% at the intra-assay level and from 10% to 16% at the inter-assay level, underscoring result reliability and consistency. In males, the highest serum T and fAM levels were recorded concurrently with the presence of spermatozoa in samples collected via EE. Although females did not exhibit oviposition events, significantly higher E2 and fEM levels were observed in August compared to May, suggesting potential seasonal variations in estrogenic hormone production. Fecal androgen and estrogen levels were significantly different between sexes in August, with males having higher fAM and females having higher fEM levels. Overall, the immunoassays validated in this study were found to be efficient in diagnosing reproductive activity in owls.

Determination of Coagulation Parameters by Whole Blood Dynamic Viscoelastic Coagulometry in Strigiformes.

No reference values are available in Strigiformes to evaluate blood coagulation using dynamic viscoelastic coagulometry (DVC) with the Sonoclot (Sienco, Boulder, CO, USA) analyzer. The objectives of this study were 1) to assess the feasibility of DVC in Strigiformes, 2) to calculate the index of individuality of each coagulation parameter, and 3) to assess interspecies variability and establish reference intervals, if relevant, based on the index of individuality. Fresh whole blood samples were obtained from healthy Strigiformes, including 13 barred owls (Strix varia), 10 great horned owls (Bubo virginianus), 6 snowy owls (Bubo scandiacus), and 7 eastern screech owls (Megascops asio), and analyzed with DVC with glass bead (gb) and kaolin clay (k) coagulation activators. Activated clotting time (ACT), clot rate (CR), and platelet function were determined immediately after collection using fresh native whole blood. Intraindividual variability was assessed with a second fresh native whole blood sample from 5 barred owls. Interindividual variability was assessed using a Kruskall-Wallis test. For the parameters gbACT (n = 35), gbCR (n = 34), and kACT (n = 27), no significant differences were detected between species (all P ≥ 0.05). Based on low index of individuality, global Strigiformes reference intervals were determined for gbACT (32.3-852.5 seconds; n = 35), gbCR (0-20.1 units/min; n = 29), and kACT (0-1570.3 seconds; n = 27). In conclusion, DVC can be used in Strigiformes and the gb coagulation activator would be more appropriate when basal individual values are not available in a tested individual.

First documentation of acorn consumption by eastern screech owl (Megascops asio)

We present evidence for the first documentation of consumption of a water oak (Quercus nigra) acorn by an eastern screech owl (Megascops asio). A screech owl diet typically consists of small mammals, small birds, and arthropods. In our study, we had a 1-m x 1-m sand pad under observation from a game camera that was set on a 1-min time-lapse delay. On this sand pad, we placed five water oak acorns. In a series of six images over six minutes, we observed an eastern screech owl land near the sand pad, walk to an acorn, and appear to consume the acorn. Although there could be other plausible explanations and events that transpired between 1-min image intervals, we believe this acorn was consumed by the eastern screech owl. The importance of this addition of food type to the diet of a raptor is largely unexplored and undocumented.

Co-vocalisation of Eagle Owl and other owls in the natural and climatic conditions of the Middle Volga region

The article considers the co-vocalisation of Eagle Owl and other species of owls. The studies were carried out using digital voice recorders in the habitats of the eagle owl. The natural and climatic conditions of the area in which co-vocalisation was noted were analyzed. Rare cases of co-vocalisation of Eagle Owl and its prey, primarily the Ural Owl and the Long-eared Owl, have been identified. Co-vocalisation was revealed only in winter and spring. This is due to the breeding season of birds. The presented study reflects the environmental sustainability of a particular area.

Birds of Kanetiya area - inventory, notable sightings, and overview of seasonal changes in reporting frequency of bird species in an unprotected area of Himachal Pradesh, India

Biodiversity of unprotected areas in the western Himalayan region is under threat. Despite this, it is poorly studied and documented. The citizen science platform eBird was used to record bird species of the unprotected Kanetiya area (Darbhog panchayat), Shimla, Himachal Pradesh from August 2019–2020. Reporting frequency using this data was calculated to represent an index of species abundance. This was calculated independently for each species across three seasons and reported as a metric that can be tracked over time. One-hundred-and-twenty-four (20% of the species from Himachal Pradesh) species of birds belonging to 13 orders and 43 families were recorded. Of these, 37 (30%) were recorded year-round and the remaining 87% (80%) were migratory. The checklist consisted of five species of high conservation concern and 22 species of moderate conservation concern. This checklist also provides insights into the distributions of some species whose ranges within India are not yet well defined (Northern Long-eared Owl Asio otus, Aberrant Bush Warbler Horornis flavolivaceus, Himalayan Owl Strix nivicolum) and into migration through this part of the Himalaya (Black Stork Ciconia nigra). Locals can be educated to upload short checklists for monitoring since they have helped the local forest department’s conservation efforts.