Owl Species Research Articles

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.

Spatio‐temporal shift in body size and plumage coloration is associated with the magnitude of climate change in a cosmopolitan owl

AbstractAimClimatic gradients shape geographic variation in phenotypic traits that are involved in animal thermoregulation. Therefore, increasing temperatures under global warming are expected to cause change over time in traits that show predictable spatial patterns according to environmental clines (body and appendage size, tegument coloration), as well exemplified by biogeographic rules and shown by increasing literature at a local scale. However, whether temporal shifts in phenotypic traits vary spatially according to the magnitude of the change in local climatic conditions is still unknown.LocationWorld.TaxonBarn owl species complex (Tyto alba group).MethodsBy using thousands of museum specimens collected across the globe from 1901 to 2018, we calculated within‐population change over time in wing length, bill length and melanin‐based plumage coloration and examined whether these trends differed across geographic regions, latitudes and gradients of climate changes.ResultsWe showed that populations exposed to an increasing warmer climate were subjected to a more marked decrease in body size, as gauged by wing length, and also absolute bill length that displayed a similar, although less steep, pattern of shrinking over time. In addition, phaeomelanin‐based ventral plumage colour has become paler in regions where the climate changed into warmer and drier, and darker where both temperature and precipitation increased.Main ConclusionsThese trends are generally coherent with the predictions based on Bergmann's and Gloger's rules, but not Allen's rule, and suggest that temporal shifts in body size and tegument colour depend on the magnitude of the alteration in climatic conditions, with populations living in regions where the climate has changed the most that are subjected to more marked phenotypic changes. Spatio‐temporal variation in climate has driven within‐species phenotypic clines, and it is expected to increase differences among populations according to the predicted further climate change.

Perceptions, Knowledge, and Emotions About Owls in Southern Ecuador

Owls hold significant utilitarian and aesthetic values for humans, ranging from pest control to ecotourism. However, cultural beliefs rooted in negative perceptions and emotions have led to conflicts and threats to many owl species. In South America, research on the relationship between owls and people is limited. This study aims to identify the variables involved in the construction of social knowledge, perceptions, and emotions toward owls. Face-to-face questionnaires were administered to residents in southern Ecuador. The data were analyzed using decision trees, a novel approach in ethnobiology. The results indicate that participants exhibited accurate knowledge of owl diet and habitat, with a majority having previous owl sightings and familiarity with their vocalizations. These factors, along with the sources informing their knowledge (such as school and family), contribute to the development of neutral perceptions and emotions toward these birds. The majority of participants recognize the importance of owls for the environment and support their conservation, with these two variables playing a crucial role in shaping positive emotions. Additionally, perceptions and emotions are primarily influenced by the region of residence. The presented data provide valuable insights into the significance of social perceptions and emotions in designing strategies to mitigate intentional owl mortality and persecution resulting from misconceptions and misperceptions.

Live owls in Japanese pet stores and cafés: Volumes, species, and impediments to effective trade monitoring

Owls are popular pets in Japan, with the country being the largest importer of live owls in the world. Although several studies have looked at the welfare implications of the country's “owl cafés,” the scale and scope of the Japanese owl trade, and its potential consequences for conservation, remain largely unexplored. Here we present an overview of the volumes and species of owl found in a selection of Japanese pet stores and cafés, based on two physical surveys, an online survey, and an analysis of CITES import data. We found a high number of owls (n = 1914) from a large variety of species (n = 49) across a total of 92 establishments. CITES import records show that species variety has highly increased over time. Although the majority of owls in Japanese pet stores and cafés are likely to be of captive-bred origin, trade histories are often difficult to trace, and the legality of parent stock is impossible to determine. Further complicating monitoring efforts are gaps in international trade data, the mislabeling of species, selective breeding, and the use of outdated taxonomy. Considering the large scale of the Japanese market, efforts to facilitate the improved monitoring of the owl trade are highly warranted to ensure its legality and sustainability.

Habitat and species segregation of Strigiformes in the Brazilian Atlantic Forest

The order Strigiformes contains approximately 250 owl species distributed worldwide, and the majority of them live in forests. Although basic information is available on many owls, few have been studied in-depth; consequently, little is known about the role of vegetation in their lives. This study aimed to investigate Strigiformes in a fragment of the Atlantic Forest using point count surveys conducted from January 2018 to December 2019. Twelve points were sampled for 30 min/month, totaling 144 h. Data on vegetation structure were collected for analysis. The numbers of individuals and species were then estimated. Twenty-six individuals of four species were recorded: 12 Strix virgata, 6 Pulsatrix koeniswaldiana, 5 Megascops atricapilla, and 3 Megascops choliba. Strix virgata was associated with sites with typical mature forest characteristics, although it tolerated variation in some parameters (e.g., average canopy height). Pulsatrix koeniswaldiana was a generalist in terms of habitat characteristics, even when using edge areas. Megascops choliba was scarce within the sampled area and seemed to avoid mature forest. Megascops atricapilla occurred from sites with a lower canopy to more mature forest areas. Altogether, this study highlighted the importance of conserving forest fragments in the Atlantic Forest, which harbors considerable biodiversity, especially of owls.

Vocal interaction between Tawny Owl (Strix aluco) and Ural Owl (Strix uralensis) in the Middle Volga

The work studied the co-vocalization of Tawny Owl and Ural Owl. Researched primarily using digital voice recorders. Co-vocalization was revealed only in spring. This is due to the breeding season of birds. The roll call of two species of owls was recorded 2 h 30 min after sunset. Co-vocalization was always observed from 21:00 to 22:00 hours. Duration of co-vocalization of the Tawny Owl and the Ural Owl ranged from several sec to 6 min. During periods of co-vocalization, the Tawny Owl managed to produce twice as many calls as the Ural Owl. The Tawny Owl was the first to start calling, and later the calls of the Ural Owl joined it. The Tawny Owl stopped vocalizing, and the Ural Owl continued to call after it. The calls of each of the two owl species in shared habitats were recorded primarily at different times. More often, the Tawny Owl began vocalization 30 min after the Ural Owl stopped calling. The natural and climatic conditions of the area in which co-vocalization was noted were studied. Co-vocalizations were observed in the temperature range from +3 to +7°C. Joint calls were recorded at wind strength from 4 to 7 m/s, at cloud cover from 40 to 90%, at pressure from 734 to 744 mm Hg.

Rozšíření myšivky horské (Sicista betulina) v Pošumaví na základě rozboru potravy sov (Rodentia: Zapodidae)

Distribution of Sicista betulina in the Šumava Mts. (Bohemian Forest, SW Bohemia, Czech Republic) based on owl diet analysis (Rodentia: Zapodidae). The Šumava Mountains are one of the three areas of a relict occurrence of the northern birch mouse (Sicista betulina) in the Czech Republic. The present study summarises all records of this species obtained there by the analysis of diet of three species of owls, the Tengmalm’s owl (Aegolius funereus), to a lesser extent of the Ural owl (Strix uralensis) and tawny owl (Strix aluco). A total of 355 sample sets from 228 localities was processed, positive findings concern 57 localities where the northern birch mouse was found (322 individuals). The presence of the species was confirmed in an area of approximately 1,400 km2, which corresponds to 13 mapping fields of the KFME, four of which extend into the territories of Germany and Austria (field numbers 7047, 7148, 7249, 7350). More than a third of the localities (37.0%) and nearly two thirds of the individuals (62.4%) come from four mapping fields (7048, 7049, 7148, 7149) covering mainly a peaty alluvial plain of the upper stream of the Vltava river and its surroundings. Data obtained by observation or capturing of the northern birch mouse give a similar picture. Thus, this territory with the high proportion of relict vegetation can be considered as the core area of the current occurrence of the mouse in the Šumava Mts. The altitude range of the northern birch mouse records from owl pellets is 680–1160 m a. s. l. with a mean of 871.7 m a. s. l. Almost a third of the localities (32.0%) lie in the altitudinal range of 700–800 m a. s. l., and more than four fifths of the records (82.7%) fall within the range of 700–1000 m a. s. l. However, these are only indicative values that can be influenced by the size of the individual hunting territories of owls (especially in a landscape with a steep mountainous relief). Our results confirm the previously described zoogeographical profile of the northern birch mouse in the Šumava Mts., i.e., that its distribution is limited only to the south-eastern half of this mountain range and ends roughly in the Kvildské pláně region in the north-west. Records of the northern birch mouse on the Bavarian side of the mountain range are in full agreement with this. It can be assumed that the species occurrence in the whole Bohemian Forest is primarily shaped by its Holocene history. Furthermore, it has been confirmed that the analysis of the diet composition of the Tengmalm’s owl is an effective method of study of the geographical distribution of the northern birch mouse.

Climate Change Habitat Model Forecasts for Eight Owl Species in the Southwestern US.

The high-resolution forecasting of vegetation type shifts may prove essential in anticipating and mitigating the impacts of future climate change on bird populations. Here, we used the US Forest Service Ecological Response Unit (ERU) classification to develop and assess vegetation-based breeding habitat profiles for eight owl species occurring in the foothills and mountains of the Southwestern US. Shifts in mapped habitat were forecast using an ecosystem vulnerability model based on the pre-1990 climate envelopes of ERUs and the Intergovernmental Panel on Climate Change's (IPCC) A1B moderate-emission scenario for the future climate. For five of the eight owl species, the regional breeding habitat extent was projected to decline by at least 60% by 2090. Three species, the boreal owl (Aegolius funereus; at the trailing edge of its distribution), flammulated owl (Psiloscops flammeolus), and northern pygmy-owl (Glaucidium gnoma), were projected to experience the steepest habitat loss rates of 85%, 85%, and 76%, respectively. Projected vegetation shifts overlaid with well-documented flammulated owl breeding populations showed the complete or near complete loss of habitat by 2090 in areas of montane forest currently supporting dense aggregations of owl territories. Generalist or lower-elevation owl species were predicted to be less impacted, while, for the whiskered screech-owl (Megascops trichopsis), the contraction of the current habitat was nearly offset by a projected northward expansion. In general, the results of this study suggest high exposure to climate change impacts for the upper-elevation forest owls of semi-arid Southwestern North America. Long-distance migration and low natal philopatry may prove important to some montane owl populations in adapting to the regional loss of habitat.

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.

Binocular field configuration in owls: the role of foraging ecology.

The binocular field of vision differs widely in birds depending on ecological traits such as foraging. Owls (Strigiformes) have been considered to have a unique binocular field, but whether it is related to foraging has remained unknown. While taking into account allometry and phylogeny, we hypothesized that both daily activity cycle and diet determine the size and shape of the binocular field in owls. Here, we compared the binocular field configuration of 23 species of owls. While we found no effect of allometry and phylogeny, ecological traits strongly influence the binocular field shape and size. Binocular field shape of owls significantly differed from that of diurnal raptors. Among owls, binocular field shape was relatively conserved, but binocular field size differed among species depending on ecological traits, with larger binocular fields in species living in dense habitat and foraging on invertebrates. Our results suggest that (i) binocular field shape is associated with the time of foraging in the daily cycle (owls versus diurnal raptors) and (ii) that binocular field size differs between closely related owl species even though the general shape is conserved, possibly because the field of view is partially restricted by feathers, in a trade-off with auditory localization.

Colour-specific diet specialization is associated with differences in owlet weight in a polymorphic owl: influence of the trophic quality variation.

The niche divergence hypothesis proposes that the evolution and maintenance of colour polymorphism is based on a mechanism of disruptive selection. In a trophic context, the hypothesis predicts that individuals differing in colour vary in their trophic niche, either because they differ in foraging efficiency or feed in different habitats. A major evolutionary conundrum is how these expectations are affected by variation in trophic quality. Using an owl species with colour plumage polymorphism, the Eurasian scops owl Otus scops, we examined diet and habitat segregation during reproduction in relation to plumage colouration and trophic quality. Intensive sampling revealed that trophic quality for scops owls (i.e. abundance of grasshoppers and locusts) varied more among territories than between years, but scops owls did not segregate among territories of different quality by their colouration. However, we found that sex, plumage colouration and territory differences in trophic quality explained differences in the degree of dietary specialization. Brownish males delivered a higher diversity of prey to the nest than greyish ones in high trophic quality territories. We also found that the more diverse the diet provided by males, the heavier the owlets at fledging. Our study provides evidence for a different sensitivity to trophic quality of the colour morphs with potential fitness consequences in scops owls. We highlight the importance of studying the mechanisms leading to the persistence of colour polymorphism in patchy environments, since segregation may pass otherwise unnoticed if only habitats or years with similar conditions are considered.

The role of leading-edge serrations in controlling the flow over owls’ wing

We studied the effects of leading-edge serrations on the flow dynamics developed over an owl wing model. Owls are predatory birds. Most owl species are nocturnal, with some active during the day. The nocturnal ones feature stealth capabilities that are partially attributed to their wing microfeatures. One of these microfeatures is small rigid combs (i.e. serrations) aligned at an angle with respect to the incoming flow located at the wings’ leading-edge region of the primaries. These serrations are essentially passive flow control devices that enhance some of the owls’ flight characteristics, such as aeroacoustics and, potentially, aerodynamics. We performed a comparative study between serrated and non-serrated owl wing models and investigated how the boundary layer over these wings changes in the presence of serrations over a range of angles of attack. Using particle image velocimetry, we measured the mean and turbulent flow characteristics and analyzed the flow patterns within the boundary layer region. Our experimental study suggests that leading-edge serrations modify the boundary layer over the wing at all angles of attack, but not in a similar manner. At low angles of attack (<20°), the serrations amplified the turbulence activity over the wing planform without causing any significant change in the mean flow. At 20° angle of attack, the serrations act to suppress existing turbulence conditions, presumably by causing an earlier separation closer to the leading-edge region, thus enabling the flow to reattach prior to shedding downstream into the wake. Following the pressure Hessian equation, turbulence suppression reduces the pressure fluctuations gradients. This reduction over the wing would weaken, to some extent, the scattering of aerodynamic noise in the near wake region.

Owl-mediated diploendozoochorous seed dispersal increases dispersal distance and supports seedling establishment

Seed dispersal is an essential process contributing to the maintenance of plant populations. Zoochory is a widespread way of plant dispersal in every terrestrial ecosystem that can ensure the long-distance dispersal of seeds. Secondary seed dispersal (SSD) by far-ranging raptors is a special type of zoochory, which might have a role in colonizing new habitats. We used the barn owl (Tyto alba) as model species to test the effectivity and seasonality of SSD in open semi-natural landscapes. We collected 582 pellets from six sites in East-Hungary throughout one year. We identified prey items in the pellets and determined the viable seed content of the pellets by germination experiments. We found that herbivorous Microtus arvalis L. was the most abundant prey item through which most of the seeds spread. Owls dispersed the seeds of generalist and disturbance-tolerant plants, indicating the habitat type where small mammals occur abundantly. In another experiment we tested the effect of the pellet material on the seedling survival and found that prey remains enhanced establishment of seedlings. Our study suggests that SSD by barn owl is occasional but important event in long-distance seed dispersal. Since the studied owl species uses several habitat types and has larger mobility than the rodents, the revealed dispersal mechanism can considerably increase seed dispersal distance and seed exchange between habitat types.

Anthropogenic threats to owls: Insights from rehabilitation admittance data and rodenticide screening in Texas.

Owls (Strigiformes) provide myriad ecosystem services and are sentinels for ecosystem health. However, they are at continued risk from anthropogenic threats such as vehicle collisions, entanglement with human-made materials, and exposure to anticoagulant rodenticides (ARs), a widespread pesticide known to affect owls. Texas is an important region for numerous migratory and non-migratory owl species in the United States (US), yet assessments of threats owls face here are lacking preventing the development of informed conservation strategies. This study coupled assessment of admittance data from two wildlife rehabilitation centers in Texas with AR liver screening to (1) identify which species of owls are commonly admitted, (2) evaluate seasonality of admittance, and (3) assess causes of admittance for owls in Texas. Between 2010 and 2021, 1,620 owls were admitted into rehabilitation, representing eight species of which the Great-horned Owl (Bubo virginianus) was the most common. For all owls combined admittance rates were highest in the spring, driven by an influx of juveniles (n = 703, 43.40%). The leading cause of admittance amongst species was 'no apparent injury' (n = 567, 34.94%). Where clear diagnoses could be made, the leading causes of admittances were 'entrapment in human infrastructure' (n = 100, 6.11%) and 'collision with vehicles' (n = 74, 4.56%). While the admittance data did not reveal any cases of AR poisoning, liver screening demonstrated high incidences of AR exposure; of 53 owls screened for ARs, 50.94% (n = 27) tested positive with 18 showing exposure to multiple ARs. Brodifacoum was the most frequently detected AR (n = 19, 43.18%) and seven owls (25.93%) tested positive within lethal ranges. Our results suggest that owls in Texas are at risk from myriad anthropogenic threats and face high exposure rates to ARs. In doing so, our results can inform conservation strategies that mitigate anthropogenic threats faced by owls in Texas and beyond.

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.

The diurnal habits of a long-gone Tibetan Owl

Owl’s nocturnal habits stand out from most birds, and in various cultures they are associated with wisdom or even the magical world of Harry Potter. We describe here a unique fossil of an extinct owl species that was instead active during the day. This species links to some of the few daytime active owls and fills in a six-million-year gap in their evolutionary history.

Cavity-breeding birds create specific microhabitats for diverse arthropod communities in boreal forests

The nests of secondary cavity-nesters located in tree cavities may form specific microhabitats of conservation importance due to their limited accessibility and availability. Species-specific nesting materials in nests of different secondary cavity-nesters may furthermore provide very different microhabitats for arthropods. The potential differences in arthropod communities inhabiting nests of different bird species in excavated cavities or nest boxes have, however, rarely been studied despite their relevance for conservation. Here we investigated the diversity and composition of arthropod communities in these different cavity types and bird species’ nests in managed boreal forests. We identified morphologically and by DNA-metabarcoding arthropods in nest materials that were collected in and compared between (i) woodpecker-size cavities from seven different combinations of cavity type (nest box or excavated cavity), tree species (aspen or pine) and accumulation history of nest materials (single-season cleaned or uncleaned nest boxes that accumulated nests of passerines or an owl species); and (ii) nests of two different passerine species in small nest boxes. We identified 64 arthropod taxa in ten orders, from which Diptera, Coleoptera, Siphonaptera, and Lepidoptera were the most abundant. Shannon diversity index was similar among the cavity-nest-type combinations, but taxa richness was the highest in the owl nests. The arthropod communities (especially Histeridae beetles) deviated most from the other types of nests in owl and aspen cavity nests with more advanced decomposition of nest material (soil or wet environment related taxa). The differences in arthropod communities between the different nest types point out the importance of the ecological chain “tree cavities—bird nests—arthropod communities”.

Owls’ responses to forest conservation in the Alps

Abstract As inhabitants of cavities, some owl species benefit from natural processes, different tree compositions and higher volumes of dead wood. We assumed that protected areas would have a positive impact on the owl community. We compared the abundance of calling owls on 22 lines in managed versus protected forests. Here, we recorded the acoustic communication of owls. The composition of the owl community did not differ between areas. However, we found the impact of forest landscape integrity index and altitude on the diversity of owls. Forests in protected areas probably need time to develop natural and heterogeneous habitat structures. The conservation priority should be to increase the integrity of the forests. Our results also confirmed that managed forests can have a high diversity of owls.

Morphologic and Genetic Analysis of Synhimantus (Synhimantus) laticeps from a Long-Eared Owl (Asio otus).

The long-eared owl (Asio otus) is a medium-sized owl species that is well-distributed in almost all of the territories in Portugal. Nematodes were found in the oral cavity of a long-eared owl (A. otus) admitted to CRASSA (Wildlife Rehabilitation Centre of Santo André). During a physical exam and stabilization of the bird, five nematodes were collected. The worms were examined and measured under light microscopy, and photos were taken. After a morphological analysis was conducted, all the nematodes (five females) were identified as Synhimantus (Synhimantus) laticeps. Two specimens were subjected to molecular analysis, which confirmed the result. This study provides a combined morphological and genetic approach to S. laticeps. To the authors' best knowledge, this is the first report including genetic sequencing of S. laticeps in a long-eared owl (A. otus) from Portugal.