Owl Species Research Articles

New genome assembly of the barn owl (Tyto alba alba).

New genomic tools open doors to study ecology, evolution, and population genomics of wild animals. For the Barn owl species complex, a cosmopolitan nocturnal raptor, a very fragmented draft genome was assembled for the American species (Tyto furcata pratincola) (Jarvis et al. 2014). To improve the genome, we assembled de novo Illumina and Pacific Biosciences (PacBio) long reads sequences of its European counterpart (Tyto alba alba). This genome assembly of 1.219 Gbp comprises 21,509 scaffolds and results in a N50 of 4,615,526 bp. BUSCO (Universal Single‐Copy Orthologs) analysis revealed an assembly completeness of 94.8% with only 1.8% of the genes missing out of 4,915 avian orthologs searched, a proportion similar to that found in the genomes of the zebra finch (Taeniopygia guttata) or the collared flycatcher (Ficedula albicollis). By mapping the reads of the female American barn owl to the male European barn owl reads, we detected several structural variants and identified 70 Mbp of the Z chromosome. The barn owl scaffolds were further mapped to the chromosomes of the zebra finch. In addition, the completeness of the European barn owl genome is demonstrated with 94 of 128 proteins missing in the chicken genome retrieved in the European barn owl transcripts. This improved genome will help future barn owl population genomic investigations.

Aeroacoustics of Silent Owl Flight

The ability of some species of owl to fly in effective silence is unique among birds and provides a distinct hunting advantage, but it remains a mystery as to exactly what aspects of the owl and its flight are responsible for this dramatic noise reduction. Crucially, this mystery extends to how the flow physics may be leveraged to generate noise-reduction strategies for wider technological application. We review current knowledge of aerodynamic noise from owls, ranging from live owl noise measurements to mathematical modeling and experiments focused on how owls may disrupt the standard routes of noise generation. Specialized adaptations and foraging strategies are not uniform across all owl species: Some species may not have need for silent flight, or their evolutionary adaptations may not be effective for useful noise reduction for certain species. This hypothesis is examined using mathematical models and borne out where possible by noise measurements and morphological observations of owl feathers and wings.

Iris Yellowness Relates to Age and Individual Quality in Two Owl Species

Birds show huge variation in color displays evolved for communication. However, among colored phenotypic traits, eyes remain largely overlooked, with only a few studies suggesting a potential signaling function or a role in mate recognition and crypsis. Iris color is a remarkably striking feature in the wholly cryptic pattern of many owls, and may potentially play a signaling function, a possibility so far neglected. Here, we studied variation and potential signaling of iris yellowness as an indicator of quality in parent-offspring communication and other social contexts in the Little Owl (Athene noctua) and Eurasian Scops-Owl (Otus scops). Yellowness did not differ between the sexes; however, adults of the two species had more intensely yellow irises than owlets. Most of variation in iris yellowness of owlets occurred between rather than within nests and seemed to be linked to parental qualities of Little Owls, but was unrelated to condition among Eurasian Scops-Owl owlets. In adults, however, we found that iris yellowness of females was positively associated with nest success (an index of female fitness) in Little Owls, but not in Eurasian Scops-Owls. This study suggests that iris color variation is unlikely to play a role in parent-offspring communication for these two owl species, but that iris yellowness of female Little Owls may potentially play a signaling role in social contexts, a possibility that should be studied in the future.

Spatial and Temporal Changes in Falconiformes and Strigiformes Nutrition: Causes, Significance, Consequences

Spatial and temporal changes in the nutrition of four species of diurnal birds of prey and six species of owls, traditionally referred to polyphages (generalists), are considered. Based on the literature data and our own observations, we have provided a classification of birds of prey according to their feeding and nest building characteristics. The main ways of interaction of these aspects of raptors` life and the importance of their understanding for the effective planning and development of measures for the conservation of the studied species are presented

Association between Landscape Features and Owl Assemblages in a Tropical Rainforest of Southeastern Mexico

Tropical owls are one of the most threatened groups of birds. Studying the association between landscape features and owl assemblages is challenging due to the logistical difficulties of nocturnal fieldwork. We analyzed the association of landscape composition and spatial configuration of forest cover with the composition of the owl assemblages in a tropical rainforest in southeastern Mexico. During the 2014 reproductive season (April to June), we estimated owl abundance through auditory detection and playbacks at 60 survey points distributed in 12 landscapes (625 ha each) within a gradient of forest cover. We found that the owl community comprised six out of the 10 expected resident species. The landscape unit with 41% forest cover contained the most diverse assemblage. The owl species most susceptible to local extinction were specialists of interior areas of old-growth forest. The abundances of the Middle American Screech-Owl (Megascops guatemalae), Great Horned Owl (Bubo virginianus), and Black-and-white Owl (Ciccaba nigrolineata) were positively associated with the proportion of forest cover as well as with the average size of the patches, but negatively associated with environmental temperature. The abundances of the Barn Owl (Tyto alba) and Ferruginous Pygmy-Owl (Glaucidium brasilianum) were positively related to the amount of urban area in the landscape. The only species recorded along the entire gradient was the Mottled Owl (Ciccaba virgata), a species that is a generalist in habitat and diet; its abundance was positively related to the proportion of forest cover and the amount of water surface (lakes and rivers) in the landscape. Four resident species were not recorded: Crested Owl (Lophostrix cristata), Spectacled Owl (Pulsatrix perspicillata), Striped Owl (Pseudoscops clamator), and Central American Pygmy-Owl (Glaucidium griseiceps).

Is there an owl species on St Matthias (Mussau) Islands, Papua New Guinea?

In July 2019, during a short ornithological visit to the St Matthias (Mussau) Islands, Papua New Guinea, we recorded a sound that might have been from an owl on the small island of Emussau close to Mussau. No owl or nightjar is known to occur on these islands. The bird’s call shows similarities but differs from other Melanesian Ninox owl species. Here we describe the call and discuss potential origins.

A comparison of urban and peri-urban/hinterland nocturnal birds at Brisbane, Australia

This study identified and compared the abundance and detectability of owls and other nocturnal birds, over 1 year, in an urban parkland of a Brisbane suburb to a peri-urban/hinterland/rainforest site 27km away. Five owl species were detected, but only at the peri-urban/hinterland/rainforest site, they were powerful owl Ninox strenua, southern boobook Ninox boobook, sooty owl, Tyto tenebricosa, masked owl Tyto novaehollandiae and barn owl Tyto alba. A single southern boobook was detected outside the study, at the urban site. The tawny frogmouth Podargus strigoides was only detected at the urban site whereas the plumed frogmouth Podargus ocellatus plumiferus was only detected at the rainforest site. The bush stone-curlew Burhinus grallarius was the most frequently detected nocturnal species, yet we discuss its recent decline in Brisbane. Incidentally recorded mammals, reptiles, frogs and diurnal birds are given. The rainforest site had more scansorial mammals whereas the urban site had more possums, dogs and cats.

The use of plant stratification by Otus jolandae in the Natural Tourism Park of Kerandangan, Lombok

Otus jolandae is an endemic owl species of Lombok island. The previous study suggested exploring the ecology-related aspects more deeply since this species had been just identified in 2013 but their recent status is nearly threatened. This study was conducted in Natural Tourism Park (NTP) of Kerandangan forest from July to September 2016. The field observation was carried out during the night to observe the owl occurrence in different plant species and different vegetation structure (seedling, sapling, pole, and tree). The results reveal the most widely used plant species is Dalbergia latifolia and then followed by Tectona grandis, Tamarindus indica, Samanea saman, Mangifera indica, Delonix regia, and Swietenia mahagoni respectively. Moreover, about 71.6% Otus jolandae occurs dominantly in the tree structure, followed by 28.4% of the pole structure, while no occurrence found in seedling and sapling structure. This indicates the adult and subadult vegetation act as a critical part for being a territory for Otus jolandae. Hence, addressing the deforestation problem and at the same time protecting the forest in a good shape with more pole and tree vegetation structure will keep Otus jolandae population from the extinction.

Diet and behavior of the burrowing owl (Athene cunicularia) in Atiquipa, an ecosystem of Lomas in the south of Peru

Abstract. Luque-Fernández CR. 2019. Diet and behavior of the burrowing owl (Athene cunicularia) in Atiquipa, an ecosystem of Lomas in the south of Peru. Biodiversitas 20: 137-143. The study of trophic and behavioral habits is a fundamental aspect in the knowledge of the natural history of species, especially for those that present a wide range of distribution and that have to adapt to the habitats and available resources that can find to survive. The diet and behavior of Athene cunicularia were studied in a peculiar ecosystem such as the lomas formation, on the arid coast of southern Peru. The analysis of regurgitated pellets from a family group of Athene cunicularia was used and complemented with the monitoring of behavior through the use of trap cameras and direct observations. The results show that the diet during the months of study was based on a high proportion of invertebrate beetles (Tenebrionidae) and scorpions, also finding remains of vertebrates, including rodents, birds and highlighting the presence of a species of marsupial mouse. On the study of behavior, marked and recurrent activities are established during the day for this species, where grooming sessions are frequently reported, as well as interaction with a possible predator of this owl species. These results contribute to the understanding of the trophic relationship and its role in the studied lomas ecosystem, which is added to the importance of this species in the conservation of diversity in desert ecosystems.

Extensive paraphyly in the typical owl family (Strigidae)

AbstractThe typical owl family (Strigidae) comprises 194 species in 28 genera, 14 of which are monotypic. Relationships within and among genera in the typical owls have been challenging to discern because mitochondrial data have produced equivocal results and because many monotypic genera have been omitted from previous molecular analyses. Here, we collected and analyzed DNA sequences of ultraconserved elements (UCEs) from 43 species of typical owls to produce concatenated and multispecies coalescent-based phylogenetic hypotheses for all but one genus in the typical owl family. Our results reveal extensive paraphyly of taxonomic groups across phylogenies inferred using different analytical approaches and suggest the genera Athene, Otus, Asio, Megascops, Bubo, and Strix are paraphyletic, whereas Ninox and Glaucidium are polyphyletic. Secondary analyses of protein-coding mitochondrial genes harvested from off-target sequencing reads and mitochondrial genomes downloaded from GenBank generally support the extent of paraphyly we observe, although some disagreements exist at higher taxonomic levels between our nuclear and mitochondrial phylogenetic hypotheses. Overall, our results demonstrate the importance of taxon sampling for understanding and describing evolutionary relationships in this group, as well as the need for additional sampling, study, and taxonomic revision of typical owl species. Additionally, our findings highlight how both divergence and convergence in morphological characters have obscured our understanding of the evolutionary history of typical owls, particularly those with insular distributions.

Scavenging by Owls: A Global Review and New Observations from Europe and North America

Scavenging is an important ecological function that increases individual fitness and transfers energy between trophic levels. Scavenging by owls has been documented opportunistically through direct observations, camera trapping, and pellet analyses, but it is unknown how frequent or widespread the behavior is. We documented three new scavenging events from North America and Europe, and also performed a systematic literature review of the reports documenting scavenging by owls. The number of such reports was similar in each decade from the 1970s to the 2000s, but the decade of the 2010s had more reports than all previous decades combined. Owls scavenged primarily on mammals (81%), followed by birds (16%) and reptiles (3%); almost half (47%) of carrion scavenged were Artiodactyla (hoofed mammals) and most of the species scavenged were larger than the feeding owl. Most reports documenting scavenging by owls were from either Europe (n=14) or North America (n=11), with few reports from Asia (n=2), South America (n =2), or Australia (n=1), and none from Africa. The most frequent type of report was direct observations (n= 14), followed by camera trapping (n=9) and pellet analyses (n=6). Our review indicates that scavenging is a widespread behavior among owl species, but most observations were opportunistic, suggesting that additional incidents of scavenging by owls are likely unobserved. Further research is needed to establish the frequency of scavenging by owls and the effects that scavenging may have on owl populations and scavenging communities.

LWS visual pigment in owls: Spectral tuning inferred by genetics

Owls constitute a diverse group of raptors, active at different times of the day with distinct light conditions that might be associated with multiple visual adaptations. We investigated whether shifts in the spectral sensitivity of the L cone visual pigment, as inferred by analysis of gene structure, could be one such adaptive mechanism. Using Sanger sequencing approach, we characterized the long wavelength-sensitive (LWS) opsin gene expressed in the retina of five owl species, specifically chosen to represent distinct patterns of activity. Nocturnality was epitomized by the American barn owl (Tyto furcata), the striped owl (Asio clamator), and the tropical screech owl (Megascops choliba); diurnality, by the ferruginous pygmy owl (Glaucudium brasilianum); and cathemerality, by the burrowing owl (Athene cunicularia). We also analyzed the presence of the L cone in the retinas of four species of owl (T. furcata, A. cunicularia, G. brasilianum and M. choliba) using immnunohistochemistry. Five critical sites for the spectral tuning of the LWS opsin (164, 181, 261, 269, and 292) were analyzed and compared to the sequence of other birds. The sequence of A. cunicularia showed a substitution on residue 269, with the presence of an alanine instead threonine, which generates an estimated maximum absorption (λmax) around 537 nm. No other variation was found in the spectral tuning sites of the LWS opsin, among the other species, and the λmax was estimated at around 555 nm. The presence of L cones in the retinas of the four species of owls was revealed using immunohistochemistry and we observed a reduced number of L cones in T. furcata compared to A. cunicularia, G. brasilianum and M. choliba.

Increased Food Provisioning by Female Montagu's Harriers in Years with Food Shortage Weakens Sex-Specific Roles in Parental Care

In many owl and raptor species, sexes have distinct parental roles. Females incubate the eggs and raise the chicks until independence, while males provide females and their chicks with food. This is believed to reduce sexual conflict over parental care as tasks do not overlap. The level of parental care is also shaped by parent-offspring conflict. The scarcity of empirical data on parental investment in species with sex-specific parental roles was our motivation to study parental care in the Montagu's Harrier Circus pygargus in relation to natural annual variation in food availability (vole abundance). By tracking individual birds using GPS-trackers, several aspects of parental care (the number of food provisioning trips, home range size and nest attendance) could be quantified for different nesting phases. We found that in food-poor years, males spent less time near the nest, and had lower food provisioning rates during the incubation and nestling phases. In addition, males had larger home ranges in food-poor years, a possible indicator of increased foraging effort. In contrast, females increased their contribution to food provisioning in food-poor years, as shown by higher food provisioning rates and larger home ranges. This increased foraging effort came at the cost of lower nest attendance by females. Our data suggest that, when food abundance declines, Montagu's Harriers shift from a system with almost strict sex-specific parental roles towards a system where both parents provide the same type of care with possibly increased sexual conflict.

Acoustic Monitoring Reveals a Diverse Forest Owl Community, Illustrating Its Potential for Basic and Applied Ecology

Bioacoustic surveys are an increasingly common tool for wildlife research due to increasing software performance and decreasing hardware costs. We conducted landscape-scale passive acoustic surveys across the northern Sierra Nevada to assess the distribution and density of barred owls (Strix varia) at the leading edge of their ongoing range expansion. From the resulting audio, we derived occupancy data on barred owls and spotted owls (S. occidentalis). We also documented seven other owl species; because the audio was passively recorded, it will be possible to extract systematic monitoring data on those nine species and others. Our findings reveal the tremendous latent potential of passively recorded acoustic survey data for studying otherwise cryptic species and biological communities. Photo credit: Connor M. Wood. Photo credit: Connor M. Wood. These photographs illustrate the article “Acoustic monitoring reveals a diverse forest owl community, illustrating its potential for basic and applied ecology” by Connor M. Wood, R.J. Gutiérrez, and M. Zachariah Peery published in Ecology. https://doi.org/10.1002/ecy.2764

Investigation on Diet of Long-Eared Owl (Asio Otus) Inhabiting Fatih Natural Park (Turkey)

Pellet analyses were used to identify small mammal species in the diet of this owl species in order to reveal its ecological role. In this study, 706 pellets of Asio otus were collected from 3 different localities in Fatih Natural Park between February and March 2014. Pellets were dissolved by using 3% NaOH solution and then bones were dehydrated and identified. The aim of this study was to determine mammal composition in the diet of Asio otus inhabiting Fatih Natural Park of Yozgat Province, Turkey. Residues of bone from 1293 individuals/preys corresponding to 42377.41 g biomass in total were detected as the result of analysis. These individuals were identified to belonging to 12 mammal species ( Crocidura suaveolens , Suncus etruscus , Microtus hartingi/lydius , Microtus levis , Microtus sp., Cricetulus migratorius , Mesocricetus brandti , Apodemus sp., Apodemus sylvaticus , Apodemus whitherbyi , Mus macedonicus , and Meriones tristrami ) from 3 families and 8 genera. Microtus hartingi/lydius, which is known as agricultural pest, was dominant in the diet of Asio otus . When diversity of mammal species within the food composition was examined, Asio otus nesting in forest was found to primarily prefer agricultural and steppe areas, and was also found in woody and bushy areas. The use of Asio otus can be taken into consideration when dealing with rodent species known as agricultural pests.

Host body size and the abundance of chewing lice (Phthiraptera: Amblycera, Ischnocera) infesting eight owl species (Aves: Strigiformes) in Manitoba, Canada

AbstractSpecimens (n = 508) of eight species of owl (Aves: Strigiformes) collected from 1994 to 2017 in Manitoba, Canada, were weighed and examined for chewing lice (Phthiraptera: Amblycera, Ischnocera). The relationship between host body mass and infestation by 12 species of lice was examined. Host body mass explained 52% (P = 0.03) of the variation in mean intensity of louse infestation among hosts, due primarily to a high abundance of lice on the heaviest owl species. The relationship was due to the mean intensity of lice, and neither species richness nor the prevalence of lice was related to host body mass. For individual louse species, the relationship was due primarily to Kurodaia acadicae Price and Beer, Kurodaia magna Emerson, and an undetermined species of Kurodaia Uchida (Phthiraptera: Menoponidae) (R2 = 0.997), but not the nine Strigiphilus Mjöberg (Phthiraptera: Philopteridae) species (R2 = 0.27). Louse intensity did not increase with body size for individual birds of any of the owl species. Mean intensity is expected to increase in proportion with the size, specifically the surface area, of the host. Why that relationship holds only for one louse genus, and not for the most abundant genus of lice on owls, and weakly compared with other families of birds, has yet to be determined.

The first comprehensive survey of habitat suitability and population size for the endangered Grande Comoro Scops Owl (Otus pauliani): implications for its conservation

The Grande Comoro Scops Owl (Otus pauliani) is an endangered, rare and elusive owl species restricted to the Karthala forest, Grande Comore. This scops owl species is listed among the most threatened animals of the Comoro archipelago. The species is subjected to strong anthropogenic pressures causing a high rate of habitat loss. Little is known about the species’ population size, habitat suitability and geographic distribution, making the establishment of relevant conservation strategies difficult. In this study we assessed the population density and abundance of the species using the distance sampling approach through (1) the conventional distance sampling method (CDS), and (2) density surface modeling (DSM). Based on DSM, we applied a species distribution modeling method to investigate habitat suitability and geographic distribution of the species to close this knowledge gap. Average population density was estimated to be ca. 27 individuals km−2. We estimated a global population size of 3452 individuals. Our DSM suggested that the Grande Comoro Scops Owl has a very limited distribution (133 km2), restricted to high elevations in Grande Comore’s remaining natural forests (between 800 and 2000 m altitude). However, the currently high level of habitat disturbance and conversion of natural forest into agricultural land could render the species vulnerable to extinction. To ensure the viability of the species and the biodiversity of the Karthala forest, we suggest (1) restoring forest and securing corridors in the Karthala remnant forest; (2) avoiding the conversion of secondary forest into agricultural land, and using existing agroforestry for plantation development; (3) involving a broad community of local individuals and entities in their conservation and management.

Collision with power lines and electrocutions in birds — an analysis based on Swedish ringing recoveries 1990–2017

Recoveries of birds ringed in Sweden from the period 1990–2017 were used to analyse the occurrence of collisions with power lines and electrocutions. Out of more than 10,000 recoveries of birds found dead with finding circumstances mentioned, 8.6% was associated with power line constructions. The number of species involved was 51 and high proportions were especially evident in some species of owls and raptors. The overall proportion of recoveries caused by collision / electrocution shows a significant decrease over time. A decrease over time in the proportions of electrocution and collision was also evident when analysing finding circumstances in four species where corpses were sent to the Swedish Museum of Natural History. Information about the power line system in Sweden during the period 2007–2016 shows that the length of local power lines has decreased with about 21% during a ten-year period and that underground cables have increased with 28% during the same period. The results show that collisions with power lines have decreased more than electrocutions and this may imply that there are still many places where birds are at risk of being electrocuted.

OBSERVATIONS OF SIX REPRODUCTIVE CYCLES AND FOOD HABITS OF BROWN FISH OWL NESTING AT THE HUMAN HABITAT IN BANGLADESH

Background: Research reports on wild nocturnal bird especially Brown fish owl are very limited not only in Bangladesh but also elsewhere. Objectives: This paper describes the diet profile and physiology of reproduction of a pair of wild Brown fish owl. Materials and Methods: A breeding pair of Brown fish owl has been used the abandoned flower planting site on the window sunshade for their reproduction during six breeding cycles from 2013 to 2019. The behavior, food sources, food habits and their physiology of reproduction were observed closely and keenly for six reproductive cycles. Results: The male owl is usually brought prey by hunting at night and supplied to the female owl and their owlet at the nest but the only unconsumed prey lying on the nest were identified visually during the daytime. The most commonly recorded prey consumed by the habitat lost Brown fish owl include fish, frogs, rats, snake, birds and lizards. Investigation of all the six breeding cycles of this species of owl showed that all the six reproductive cycles were completed during the high cold winter months from end of November to early March. The egg clutch size varied from 1-2 with an average of 1.33 and the female owl alone incubated eggs and the incubation period varied from 37 to 38 days with an average of 37.5 days. The brooding and care of owlets were mainly performed by the female owl but the male owl supplied the food usually at night time. All the six reproductive cycles of the owls were successfully completed with fledged the juvenile owls between 53-63 days with an average of 59.25 days parental care with a total of breeding cycle from 91 to 101 with an average of 96.75 days. Conclusions: The objectives of the wild and zoo birds are for the conservation, research, education, recreation, ecology and economic benefits. This article would help to encourage development of bird parks, to create awareness of bird life and generate interest in ornithology and to help promote conservation of endangered species of birds by captive breeding. Keywords: Brown fish owl, Food and food habits, Physiology of reproduction, Egg clutch, Incubation period, Seasonal breeding cycle

Dental microwear and mesovear of Microtus voles before and after experimental feeding of owls

Form of expressions of dental microwear and mesovear of small mammals depends on abrasiveness, hardness and a number of other characteristics of the feed. Analysis of micro- and mesorelief is used on paleontological materials for the reconstruction of some parameters of the animals diet. Small mammals move a hard way from objects of biocenoses to fossils. Bone remains are modified in the process of accumulation and fossilization. In particular, bone remains from ornithogenous deposits were influenced to the substances of the digestive system of birds. In this work, an experimental estimation was made of the degree of changes in a number of characteristics of narrow-headed vole molars (Microtus gregalis) from the pellets of two species of owls. On the same samples before and after exposure to substances of the digestive system of a Polar Owl (Nyctea scandiaca) and Eagle Owl (Bubo bubo), it was shown that the microrelief of the tooth enamel undergoes serious changes and haven't information about the in vivo diet of the voles. A different degree of preservation of the mesoreliefs characteristic was shown. An assessment of their applicability for paleoreconstructions depending on this was given.