Asio Otus Research Articles

Rehabilitation of a whiskered screech-owl (Megascops trichopsis) in a wildlife care center in Mexico City

A whiskered screech-owl (Megascops trichopsis), the second smallest owl of the genus Megascops in Mexico, was admitted at the Wildlife Care Center of El Pedregal de San Angel Ecological Reserve. After performing the physical examination we found no pathologies, but the owl was not able to fly or to hunt successfully. Based on these we determined that the owl was candidate for rehabilitation for the purpose of reintroducing it to the wild. During the rehabilitation, short indoor, long outdoor and vertical flights were carried out. In addition, we offered different live preys to simulate hunting behavior. After rehabilitation, we take blood and fecal samples. Also, a complete ophthalmological examination was carried out. Before the release, a general physical evaluation was carried out where the owl showed an adequate weight (120 g). We did not find endoparasites, or alterations in the ophthalmological exam. The owl was alert and elusive, with no signs of habituation to human contact. Also, a successful flight and hunting behavior was observed. Their hematological values were within the optimal ranges reported for Megascops asio and Asio flammeus. This is the first report of hematological and biochemical values of this species.

Colonial wintering of Long-eared owl (Asio otus) in Botoșani County (N-E Romania)

Colonial wintering of Long-eared owl (Asio otus) in Botoșani County (N-E Romania)

Effects of Bionic Volute Tongue on Aerodynamic Performance and Noise Characteristics of Centrifugal Fan Used in the Air-conditioner

The aerodynamic noise generated by the centrifugal fan used in the air conditioner is related to the comfort of human living and working, which can be controlled by using the bionic design and optimization of key components of centrifugal fan. Inspired by the non-smooth leading edge of long-eared owl wing, eight kinds of volute tongues are proposed to reduce the aerodynamic noise of a centrifugal fan. The flow and sound characteristics are numerically investigated by incorporating computational fluid dynamics and computational aero-acoustics. The optimal result exhibits a noise reduction of up to 1.5 dB with a slight increase in mass flow rate. The acoustic characteristics, with respect to the sound pressure level, power spectral density, and sound directivity are discussed. The time-domain, frequency-domain, and root mean square values of pressure fluctuation are monitored and analyzed to assess the unsteady flow interaction between the volute tongue and impeller. The intensity and scale of vortices in the centrifugal fan are suppressed in the upstream and downstream of the bionic volute tongue, and the turbulence effect on the surface of the volute tongue becomes even and weak.

Bioaccumulation potential of bisphenols and benzophenone UV filters: A multiresidue approach in raptor tissues

Environmental exposure to bisphenols and benzophenone UV filters has received considerable attention due to the ubiquitous occurrence of these contaminants in the environment and their potential adverse health effects. The occurrence of bisphenols and benzophenone UV filters is well established in human populations, but data is scarce for wildlife, and especially for raptors (birds of prey, falcons and owls). In this study, concentrations of eight bisphenols and five benzophenone UV filters were determined in six raptor tissues, including muscle, kidney, liver, brain, preen gland (uropygial gland) and adipose. The tissue samples (n = 44) were taken from dead raptor species (1997–2011), including Eurasian sparrowhawks (Accipiter nisus, n = 2) and long-eared owls (Asio otus, n = 2), both from France, and white-tailed eagles (Haliaeetus albicilla, n = 16) from Greenland. Overall, six bisphenols and four benzophenone UV filters were found in the samples. Bisphenol A (BPA), bisphenol F (BPF), benzophenone-8 (BzP-8) and 4-hydroxybenzophenone (4-OH-BzP) were the most abundant contaminants, accounting for median concentrations of 67.5, 3.01, 27.1 and 9.70 ng/g wet weight (w.w.), respectively. The potential role of the preen gland as a major excretory organ for bisphenols and benzophenone UV filters was suggested since the median sum concentration of the two contaminant classes in the white-tailed eagle tissues showed higher bioaccumulation potential in the preen gland (5.86 ng/g w.w.) than the liver (2.92) and kidney (0.71). The concentrations of these contaminants in the tissues of the three raptor species indicated a pattern of increasing detection rates and median concentrations with an increase of the species size and their expected trophic position. To the best of our knowledge, this is the first peer-reviewed study to document multiresidues of both contaminant classes in raptor tissues.

Maximizing detection probability for effective large‐scale nocturnal bird monitoring

AbstractAimOur specific objectives were to (a) estimate detection probabilities of nocturnal bird species, after taking into account survey‐specific covariates, and (b) investigate the influence of site‐specific covariates on owl and nightjar abundance, integrating effects of imperfect detection.InnovationWe conceived a survey protocol to estimate probabilities of detection and estimates of abundance of owls and nightjars in a large area, the Basque Country, northern Spain.Main ConclusionsOur results show that detection probability was strongly influenced by playback broadcast and by observer experience. Date irregularly affected species according to their reproductive periods, and we also found that vocal activity gradually diminished proportionally to the hour after sunset. Tawny owl (Strix aluco) was the most abundant and widely distributed species. Its abundance was positively related to forest areas (mainly pine timber forests) and decreased in large urban and agricultural areas. Open space species were less common. Barn owls (Tyto alba), little owls (Athene noctua), Eurasian scops owls (Otus scops) and long‐eared owls (Asio otus) avoided forest areas, but showed different responses to agriculture, grass‐fields, scrub and urban areas. Finally, European nightjar (Caprimulgus europaeus) was moderately frequent, and its abundance was favoured by scrub areas and, weakly, by eucalyptus patches, whereas it was negatively affected by large forest areas. We have shown that it is fundamental to consider the effects of survey‐specific covariates in the methodology design and analytical development. Our results also indicate some ecological adaptations and population changes in the nocturnal bird community following an increase in urbanization and in the extent of timber plantations, and also the simplification of natural habitats.

The Irvingtonian Avifauna of Cumberland Bone Cave, Maryland.

The early and mid-Pleistocene avian communities of North America are best known from the Rocky Mountain region and peninsular Florida. In the Appalachian Mountain region, only a small number of avian bones from mid-latitude cave deposits have been attributed to this time period. Here, I enlarge this record by reporting on bird bones from Cumberland Bone Cave in western Maryland, a well-known locality for large and small Irvingtonian mammals and other vertebrates. The taxa identified encompass ground birds, waterfowl, a hawk, two eagles, a vulture, an owl, a jay, a flycatcher, a junco or sparrow, and a finch. No purely boreal elements are confirmed as part of the avian assemblage, and all of the extant species that are positively or tentatively identified in the assemblage still occur in the region today. An immature bone referred to the Black Vulture (Coragyps atratus (Bechstein)) represents an Irvingtonian breeding record for the species in Maryland. This record occurs at the northern limit of the current breeding range for the genus. Extinct species in the assemblage include the Passenger Pigeon (Ectopistes migratorius (Linnaeus)), a large screech owl (Megascops guildayi (Brodkorb Mourer-Chauviré 1984)), and the large goose, Branta dickeyi Miller 1924. It can be argued that none of these represent the extinction of a phyletic lineage during the Irvingtonian. Based on the broad habitat preferences of modern counterparts of the birds in the assemblage, we can expect that Irvingtonian habitats near the site included mixed forest with mast-producing hardwoods and both early and later successional stages represented. There must have been fluvial, wetland, or lacustrine habitat suitable for waterbirds nearby, and probably also open woodland or grassy savannah areas, suitable for vulture foraging, turkey nesting, and booming by Ruffed Grouse.

Comparative analysis of long-eared owl (Asio otus) winter diet from two european cities – Chisinau (Republic of Moldova) and Bacau (Romania)

Comparative analysis of long-eared owl (Asio otus) winter diet from two european cities – Chisinau (Republic of Moldova) and Bacau (Romania)

Comparing Trophic Niches of Sympatric Raptors in Agricultural Landscape in Central Poland

According to basic ecological principle, species that share the same niche do not occupy the same environment for a long time, and sympatry of two or more such species provides an interesting field for the analysis of their trophic niche differentiation. To examine the potential differences in the dimensions of the trophic niche we studied the diet of three sympatric avian predators that prey on colonial Microtus rodents. The study area in central Poland is located in an agricultural landscape, composed of crop fields, as well as meadows and pastures located within a small river valley. The pellets of long-eared owl (Asio otus), barn owl (Tyto alba) and kestrel (Falco tinnunculus) were collected from the 750 m2 study site including church building and its surrounding in the spring of 2016 and 2017. The analysis of pellets provided data on a total of 4128 vertebrate prey individuals (1914 from barn owl, 1749 from long-eared owl, and 465 from kestrel). The most important prey group of all three predators were small mammals (90%, 14 species) and the most frequently preyed species was Microtus arvalis (making up 72% of vertebrate prey of long-eared owl, 59% of kestrel and 53% of barn owl). Despite the general similarity in the diet composition, there were differences in the contribution of several prey species (e.g. Soricomorpha, M. arvalis, Mus musculus, Rattus norvegicus, and Apodemus spp.) and the diversity of the diet between the predators. We conclude that the trophic niches of the studied sympatric species differ in several dimensions, including diel activity, prey size and taxon-specific feeding preferences.

Identification of two novel adenoviruses in smooth-billed ani and tropical screech owl.

Avian adenoviruses (AdVs) are a very diverse group of pathogens causing diseases in poultry and wild birds. Wild birds, endangered by habitat loss and habitat fragmentation in the tropical forests, are recognised to play a role in the transmission of various AdVs. In this study, two novel, hitherto unknown AdVs were described from faecal samples of smooth-billed ani and tropical screech owl. The former was classified into genus Aviadenovirus, the latter into genus Atadenovirus, and both viruses most probably represent new AdV species as well. These results show that there is very limited information about the biodiversity of AdVs in tropical wild birds, though viruses might have a major effect on the population of their hosts or endanger even domesticated animals. Surveys like this provide new insights into the diversity, evolution, host variety, and distribution of avian AdVs.

Traffic noise and responses to a simulated approaching avian predator in mixed‐species flocks of chickadees, titmice, and nuthatches

AbstractTraffic noise likely reaches a wide range of species and populations throughout the world, but we still know relatively little about how it affects anti‐predator behavior of populations. We tested for possible effects of traffic noise on responses to predator acoustic cues in Carolina chickadees (Poecile carolinensis), tufted titmice (Baeolophus bicolor), and white‐breasted nuthatches (Sitta carolinensis) near 14 independent feeding stations in eastern Tennessee. We compared anti‐predator calling and seed‐taking behavior in response to playbacks of predator stimuli (screech owl calls) at sites naturally exposed to traffic noise and at sites that faced relatively little traffic noise. The screech owl call playback was designed to simulate the approach of this dangerous predator to a feeder being used by these small songbirds. We found that chickadees responded consistently to the owl stimuli across different levels of traffic noise. However, titmice, and nuthatches exhibited different behavioral responses to the predator stimulus, suggesting that traffic noise masked these low‐frequency predator calls. Overall, chickadees and nuthatches showed the broadest anti‐predator behavioral responses in comparison to titmice, corroborating earlier published work with an Indiana population. Finally, populations exposed to traffic noise overall seemed less able to detect predator cues potentially masked by that noise, and future work will need to assess likely seasonal variation in these responses as well as species‐level variation in anti‐predator responses in mixed‐species groups.

Comparative analysis of long-eared owl (Asio otus) winter diet from two european cities – Chisinau (Republic of Moldova) and Bacau (Romania)

Comparative analysis of long-eared owl (Asio otus) winter diet from two european cities – Chisinau (Republic of Moldova) and Bacau (Romania)

COMPARATIVE DIET ANALYSIS OF BARN OWL (TYTO ALBA) AND LONG- EARED OWL (ASIO OTUS) IN A HABITAT ISLAND IN NORTH-CENTRAL TEXAS

AbstractPredator-prey interactions often define the coexistence of species in space and time. In this research, we are filling a regional gap in knowledge of diet composition of the barn owl (Tyto alba) and the long-eared owl (Asio otus). The study was conducted at the Lewisville Lake Environmental Learning Area (LLELA), a patch of tallgrass prairie and post oak forest surrounded by areas with large anthropogenic modifications in north-central Texas. We examined the remains found in owl pellets collected September 2016 to March 2017. Small mammals, mainly rodents, constituted 100% of the T. alba and 98.5% of the A. otus diet. The hispid cotton rat (Sigmodon hispidus) was the most common prey detected (68.2% for T. alba and 89.0% for A. otus). Diet niche breadth of T. alba was broader than that of A. otus (0.47 and 0.06, respectively), whereas mean prey size was smaller in the T. alba diet. Diet overlap between these owls was high (0.96), likely because they hunt similarly at night, on the wing, and the prey species have limited diversity. Most rodents eaten were juveniles and the sex ratio of prey was even in both owls’ diets. We highlight the value of conducting studies in such a unique and relatively pristine environment in the face of multiple threats. Additionally, although the occurrence of A. otus is rare and infrequent in the study area, we were still able to detect a difference in diet between the ubiquitous T. alba and A. otus.

Prilog poznavanju ishrane utine (Asio otus, L. 1758) tokom negnezdećeg perioda na području Kikinde

The paper presents an analysis of the diet of Long-eared Owl at the winter roosting place in Kikinda town during the autumn and winter months of 2014/2015. The osteological and odontological parts of prey items extracted from the pellets were used to investigate the diet composition of Long-eared Owl. In the result section, the composition of prey, dietary preferences, the width of the trophic niche and diet diversity were described and analyzed. Besides, a brief biogeographic overview of the small mammals' composition is given for the northern Banat district (Vojvodina Province, northern Serbia). The obtained results were compared with other similar studies from northern Serbia and the rest of the Pannonian Basin.

Inclusion body hepatitis caused by Aviadenovirus in a tropical screech owl (Megascops choliba).

In 2016, tropical screech owl (Megascops choliba) (Tso) chicks were suddenly found dead in a Japanese breeding facility. We autopsied a 9-day-old Tso and discovered white spots scattered on the liver surface. Multifocal necrosis was diffused, and macrophages had infiltrated the necrotic hepatic lesions. Hepatocytes contained numerous intranuclear inclusion bodies. Immunohistochemical staining detected Adenovirus antigen only in the liver. Next, PCR and sequencing (LC536616) identified Tso Adenovirus (TsoAd). Basic Local Alignment Search Tool (BLAST) and phylogenic analyzes suggested TsoAd is an owl Aviadenovirus. Our study contributes to an improved understanding of infectious disease among captive raptors.

On birds of Santander-Bio Expeditions, quantifying the cost of collecting voucher specimens in Colombia

Several scientific reasons support continuing bird collection in Colombia, a megadiverse country with modest science financing. Despite the recognized value of biological collections for the rigorous study of biodiversity, there is scarce information on the monetary costs of specimens. We present results for three expeditions conducted in Santander (municipalities of Cimitarra, El Carmen de Chucurí, and Santa Barbara), Colombia, during 2018 to collect bird voucher specimens, quantifying the costs of obtaining such material. After a sampling effort of 1290 mist net hours and occasional collection using an airgun, we collected 300 bird voucher specimens, representing 117 species from 30 families. Such collection represents one of the largest series obtained during the historical ornithological exploration of Santander. We report differences among expeditions regarding the capture rate in mist nets, as well as differences in the sizes of taxa collected by mist nets and airgun. We discuss results in the context of previous ornithological expeditions in Colombia, commenting issues on the biology of some species, particularly those considered as noteworthy records (e.g., Red-legged Tinamou [Crypturellus erythropus], Cinnamon Screech Owl [Megascops petersoni], Saffron-headed Parrot [Pyrilia pyrilia], Black Inca [Coeligena prunellei], and Chestnut-crowned Gnateater [Conopophaga castaneiceps]). We calculated that the costs of obtaining and curating a specimen in Colombia, including tissues for molecular analysis, was ~US$60.4 (~$196 176 COP), which is among published costs of obtaining voucher specimens in other taxa and countries. These costs must be considered an investment in scientific capital because voucher specimens will provide biological information for hundreds of years.

Effects of Isoflurane Anesthesia on the Hematologic Values of Rehabilitated Wild Owls.

Isoflurane anesthesia is commonly used for owls when they are being rehabilitated to minimize stress during treatments and procedures, as well as to ensure caretaker safety. However, the effects of isoflurane anesthesia on the hematologic response of owls are not known. To investigate the effects of isoflurane anesthesia on the hematology of owls, 3 phases of investigation were performed on the subject animals: 1) single, short manual- versus single, short isoflurane-restraint episodes (n = 12; 38%); 2) a single, prolonged isoflurane episode (n = 10; 31%); and 3) serial, short isoflurane episodes (n = 10; 31%). All owls were classified as adult, and the sex for most individuals was unknown. Twelve owls (38%) were included in phase 1: 5 great horned owls (Bubo virginianus; 42%), 2 eastern screech owls (Megascops asio; 17%), and 5 barred owls (Strix varia; 42%). A separate cohort of 10 novel owls (31%) were selected for inclusion in both phases 2 and 3: 4 great horned owls (40%), 2 eastern screech owls (20%), 2 barred owls (20%), 1 barn owl (Tyto alba; 10%), and 1 snowy owl (Bubo scandiacus; 10%). For each anesthetic episode, blood was collected within 3 minutes of capture and in 15-minute intervals according to the duration of the procedure. Phase 2 had additional blood collections with the patient awake at 2 and 24 hours after time 0 blood collection, whereas phase 3 had an additional blood collection at 24 hours after time 0 blood collection. Hematologic analyses included packed cell volume, total solids, total white blood cell count, heterophil to lymphocyte ratio, and absolute heterophil, lymphocyte, monocyte, eosinophil, and basophil counts. Total white blood cell count decreased significantly during phase 1; packed cell volume decreased significantly during phases 2 and 3; total solids decreased significantly in phase 2; phase 2 demonstrated a lymphopenia with a concurrent decrease in the heterophil to lymphocyte ratio; and phase 3 demonstrated a heteropenia and significant changes in the eosinophil count. All hematologic changes noted in the study were within appropriate reference intervals for the owls but do suggest that there are physiologic consequences of restraining and anesthetizing these avian patients.

Long-eared owls roosted in the forest, still hunted in open land

Abstract Long-eared owls’ winter roosts located within forest, compared to their winter roosts in human settlements, often escape human attention. Only minimum information has been published about winter roosts located deep in the forest. During the years 2005 to 2016, we collected long-eared owl pellets at irregularly occupied forest winter roosts. Compared to the diet at winter roosts in human settlements, the long-eared owls roosting in the forest surprisingly significantly more frequently hunted the common vole. Moreover, we did not record higher consumption of forest mammal species in the diet of owls at forest winter roosts. Long-eared owls roosting in human settlements hunted significantly more birds. The results show that, despite the location of deep forest winter roosts, long-eared owls preferred hunting the common vole, i.e. hunting in open agricultural land. The study also points out the lack of knowledge about winter roosts located deep in the forest.

Cumulative Effect of Trophic and Weather–Climatic Factors on the Population Dynamics of the Vole-Eating Birds of Prey in Their Breeding Habitats

In the period 2001–2016, the authors studied the combined effect of trophic and weather–climatic factors on the population dynamics of three vole-eating bird of prey species on the study area in northern Moscow region, Crane Homland Reserve (56.7573° N, 37.792° E). The numbers of breeding pairs of the Common kestrels (Falco tinnunculus), Long-eared owls (Asio otus) and Short-eared owls (A. flammeus), as well as abudance of small mammals, were counted in the spring and summer months every year. Different indicators characterizing the weather–climatic conditions in the study area over the period of existence of the nesting groups of bird species were calculated based on the data of the nearest meteorological station. The simulation results showed that the numbers of the Long-eared owls depended significantly only on the trophic factor (β = 0.77 ± 0.1). The numbers of breeding pairs of the Short-eared owls and the Common kestrels depended significantly on both factors. The influence of the trophic factor on the change in the numbers of predators was the higher for the Short-eared owl (β ± SE = 1.64 ± 0.16) and the less for the Common kestrel (β = 0.38 ± 0.12). For the Common kestrel, the impact of climatic and weather factors (β = 0.41 ± 0.09) on its numbers slightly exceeded that of the trophic factor. For Short-eared owl, the effect of the climatic factor (β = 0.36 ± 0.09) was 4.5 times less than that of the trophic factor. A combination of temperature and humidity in the spring period can significantly influence the amplitude and frequency of fluctuations in the numbers of the three species of birds of prey under consideration.

Microstructure of the Primary Remex of Owls (Strigiformes)

An electron microscopic study of the microstructure of the primary remiges in owls (Strigiformes) was conducted using 13 species: Nyctea scandiaca, Bubo bubo, Asio otus, Otus scops, O. sunia, Aegolius funereus, Athene noctua, Glaucidium passerinum, Surnia ulula, Strux aluco, S. uralensis, S. nebulosa, and Tyto alba. Owls have a number of species-specific microstructural primary remex characteristics that are taxonomically important. First of all, these are the structural features of the pennaceous barb, which differ markedly not only at the ordinal, but also at the species level: cross-section configuration, pith architectonics in cross- and longitudinal sections, and cuticular barb structures. This work emphasizes that the identified elements are of taxonomic significance only when comparing the specific, strictly analogous sections of the barbs in different bird species. Based on the present study, we conclude that along with the typical elements of feather architectonics characteristic of representatives of other bird orders, the owls show a number of peculiar microstructural features. Thus, as the result of an analysis of the microstructure of the owls primary remex pennaceous barb vanule, the unique features of the distal barbules and the structure of the apical section of the barb with tightly adjacent and elongate proximal and distal barbules could be distinguished. These characteristics are revealed to cause a dense fleecy structure of the vane dorsal surface and the presence of a complex of peculiar “bunches” that form the cleft edge, i.e., the purely specific traits of the owls feather that are not found in representatives of any other bird orders we have investigated.

Different alternative diets within two subgroups in a winter roost of long-eared owls

Abstract In winter 2013/2014 a roost of long-eared owls in Bojnice Spa (central Slovakia) was formed by two subgroups situated 12 meters apart from each other. The diets of both subgroups and the direction of the owls’ departure from the roost were studied at monthly intervals. Owls of the Pinus-subgroup left the roost in a significantly different direction compared with the owls in the Picea-subgroup. The common vole was the most hunted prey in both subgroups. However, comparing the alternative prey of the two subgroups, the wood mouse and other mammals were found significantly more often in pellets of the Picea-sub-group, whereas birds were more frequent in pellets of the Pinus-subgroup. Our results suggest that the different prey hunted by the two subgroups may be a consequence of diverging hunting areas with different availability of alternative prey species.