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.

Evaluation of Thermal Antinociceptive Effects of Intramuscular Hydromorphone Hydrochloride in Great Horned Owls (Bubo virginianus).

Across the Americas, great horned owls (Bubo virginianus) are often presented to veterinarians for conditions requiring pain management. Although recent studies have evaluated opioid drugs in raptor species, information in Strigiformes is lacking. The objective of this study was to evaluate the analgesic effect and duration of action of hydromorphone hydrochloride, a full µ-opioid receptor agonist, in great horned owls. In a randomized, blinded, balanced crossover study, 6 adult birds (5 females and 1 male) received hydromorphone (0.3 and 0.6 mg/kg) or saline (0.9% NaCl) solution (0.03 mL/kg; control) in the left pectoral muscle, with a 7-day washout interval between treatments. Each bird was assigned an agitation-sedation score, and the thermal foot withdrawal threshold (TFWT) was measured at predetermined times before (t = 0 hours) and after treatment administration (t = 0.5, 1.5, 3, and 6 hours). Measurements of the TFWT were obtained with a test box equipped with a thermal perch, which delivered a gradually increasing temperature 40-62°C (104-143.6°F) to the right plantar surface of the owl's foot. Compared with controls, hydromorphone at 0.3 mg/kg dose resulted in significantly higher mean TFWT at 0.5 hours (P < 0.001), 1.5 hours (P = 0.003), and 3 hours (P = 0.005), whereas the 0.6 mg/kg dose resulted in significantly higher mean TFWT from 0.5 hours (P = 0.035) to 1.5 hours (P = 0.001). Both hydromorphone doses were associated with a significant change in the agitation-sedation score (P = 0.001), consistent with mild to moderate sedation. Two owls were observed tremoring after administration of the 0.6 mg/kg dose, which was not noted after the 0.5-hour timepoint; no other adverse effects were identified. This study offers scientific evidence to support the use of a µ-opioid agonist in great horned owls for pain management. Pharmacokinetics and other pharmacodynamic studies of other pain models evaluating hydromorphone and other opioid drugs in this species are still needed.

Range-wide phylogenomics of the Great Horned Owl (Bubo virginianus) reveals deep north-south divergence in northern Peru.

The Great Horned Owl (Bubo virginianus) inhabits myriad habitats throughout the Americas and shows complex patterns of individual and geographic morphological variation. The owl family Strigidae is known to follow ecogeographic rules, such as Gloger's rule. Although untested at the species level, these ecogeographic rules may affect B. virginianus plumage coloration and body size. Previous studies have indicated that, despite this species' morphological variability, little genetic differentiation exists across parts of their range. This study uses reduced representation genome-wide nuclear and complete mitochondrial DNA sequence data to assess range-wide relationships among B. virginianus populations and the disputed species status of B. v. magellanicus (Magellanic or Lesser Horned Owl) of the central and southern Andes. We found shallow phylogenetic relationships generally structured latitudinally to the north of the central Andes, and a deep divergence between a southern and northern clade close to the Marañón Valley in the central Andes, a common biogeographic barrier. We identify evidence of gene flow between B. v. magellanicus and other subspecies based on mitonuclear discordance and F-branch statistics. Overall differences in morphology, plumage coloration, voice, and genomic divergence support species status for B. v. magellanicus.

Description of Amblyomma monteiroae n. sp. (Acari: Ixodidae), a parasite of the great horned owl (Strigiformes: Strigidae) in southern Brazil.

In 2020, adult hard ticks (males and females) were collected from great horned owls [Bubo virginianus (Gmelin, 1788)] in the coastal region in southern Brazil. The engorged females were allowed to oviposit in the laboratory and hatched larvae could be obtained. Analyses of the external morphology of the adult ticks revealed that they represent a new species, which was named Amblyomma monteiroae n. sp. Partial sequences of the mitochondrial 16S rRNA gene and the nuclear second internal transcribed spacer (ITS2) were generated from a male and a female. Their 16S rRNA haplotypes were identical to each other and closest (96% identity) to corresponding sequences of Amblyomma parvitarsum Neumann, 1901, and 90% identical to Amblyomma neumanni Ribaga, 1902. Their ITS2 haplotypes were 95.8 to 96.0 identical to the single ITS-2 partial sequence of A. parvitarsum available in GenBank. In the phylogenetic trees inferred by both 16S rRNA and ITS2 partial sequences, A. monteiroae n. sp. formed a clade with A. parvitarsum, with A. neumanni branching sister to this clade. Amblyomma monteiroae n. sp. is genetically and morphologically related to A. parvitarsum. Both tick species are unique in combining the following morphological characters: scutum extensively ornate; eyes rounded and bulging; coxa I with two moderate pointed spurs, the external longer than the internal; a single triangular short spur on coxae II-III; presence of two spines on the tibia of legs II-IV; hypostomal dentition 3/3, trochanters without spurs. However, the males of the two species can be separated by specific features in palps and festoons, whereas the females differ in specific features of the coxal spurs. The larva of A. monteiroae n. sp. can be morphologically distinguished from A. parvitarsum only by morphometry, with the former species being slightly smaller. Currently, A. monteiroae n. sp. is restricted to southern Brazil, and the only known host is B. virginianus (Strigiformes: Strigidae). The present study increases the Amblyomma Brazilian fauna to 34 species.

Blood Transfusion from a Magellanic Great Horned Owl (Bubo virginianus magellanicus) to a Barn Owl (Tyto alba): A Successful Case of Xenotransfusion.

This report describes successful transspecies blood transfusion from a Magellanic horned owl (Bubo virginianus magellanicus) to a barn owl (Tyto alba). The barn owl was admitted to a wildlife rehabilitation center with severe anemia (packed cell volume [PCV] = 6.7%) from suspected anticoagulant rodenticide poisoning. Procedures performed included patient stabilization, pharmacological treatment, and persistent monitoring following the blood transfusion. The patient's PCV was measured daily, increasing progressively, and attaining a normal value for the species (PCV > 40%) on the eighth day posttransfusion. With no possibility of obtaining a same-species donor and because of the serious condition of the patient and unfavorable prognosis, a decision was made to perform the xenotransfusion. The result was a successful recovery and ultimately the release of the owl into its natural habitat. We concluded that xenotransfusion for avian species should be considered in cases with no possibility of obtaining a homologous donor.

Distraction Osteogenesis in Two Wild Raptors.

Distraction osteogenesis was used in 2 wild raptor patients for the repair of tibiotarsal fractures. The first case was a hatching year female peregrine falcon (Falco peregrinus) admitted with an open oblique right distal tibiotarsal fracture. The fracture was surgically managed with the external skeletal fixator intramedullary pin tie-in technique (ESF-IM pin tie-in). Appropriate healing of the fracture site occurred with the ESF-IM pin tie-in. However, there was significant pelvic limb shortening of the affected leg, and the bird consequently developed pododermatitis on the contralateral foot. The second case was an adult female great horned owl (Bubo virginianus) that was admitted with a closed, partially healed, overriding right tibiotarsal fracture. Because of the advanced stage of this fracture, which presented with a fibrous callus, and the already apparent pelvic limb shortening, the ESF-IM pin tie-in was not used. Both patients were fitted with a circular external skeletal fixator (CESF), and distraction osteogenesis was performed until the length of the pelvic limb was deemed anatomically adequate. It is critical that rehabilitated raptors be released without any physical conditions that may reduce their ability to survive and reproduce in the wild. Pelvic limb shortening can potentially predispose a raptor patient to pododermatitis, even with fatal consequences, in both captive and wild environments. The orthopedic technique used here proved useful to repair the limb shortening in both raptor cases, and each bird fully recovered and was released.

Case Series: Virulent hemosporidiosis infections in juvenile great horned owls (Bubo virginianus) from Louisiana and California, USA.

A total of eight juvenile great horned owls (Bubo virginianus) were found lethargic and on the ground in spring 2015, 2016, and 2017, including one fledgling from Louisiana, USA and seven nestlings from California, USA. One bird survived to release after rehabilitation; seven birds died or were euthanized due to poor prognosis and were necropsied. Necropsy findings were similar and included general pallor of all tissues, particularly the subcutis and lungs, and enlarged liver and spleen. Histopathology revealed multi-organ necrosis, abundant meronts containing merozoites, and intracytoplasmic pigmented haemosporidian parasites in blood cells in one bird. Leucocytozoon lineages lSTOCC16 and BUVIR06 were identified by polymerase chain reaction and genetic sequencing. The systemic Leucocytozoon infections were likely associated with morbidity and mortality in these owls. A second parasite, Haemoproteus lineage hSTVAR01, was also identified in an owl from Louisiana. This is the first identification of Leucocytozoon lineages that have been associated with mortality in young great horned owls.

New data on Neodiplostomum americanum Chandler and Rausch, 1947 (Digenea: Diplostomidae), in the Great Horned Owl Bubo virginianus Gmelin, 1788 and the Eastern Screech Owl Megascops asio Linnaeus, 1758 in Mississippi, USA.

Neodiplostomum americanum Chandler and Rausch, 1947 has been reported from six species of owls in North America. At present, there are no molecular data for this species and gene sequence data from Neodiplostomum Railliet, 1919 are limited. A freshly deceased specimen of the Great Horned Owl Bubo virginianus Gmelin, 1788 and a freshly deceased specimen of the Eastern Screech Owl Megascops asio Linnaeus, 1758 were collected in Oktibbeha County, Mississippi in 2014 and 2016, respectively. Neodiplostomum americanum were recovered from both hosts. Herein, updated morphological descriptions are supplemented with gene sequence data from conserved (18S, ITS1-5.8S, ITS2, and 28S rRNA) and fast-evolving (cytochrome c oxidase subunit 1 mtDNA) regions. Preliminary phylogenetic analysis of the genus based on cytochrome c oxidase subunit 1 gene sequence data supports the placement of N. americanum within a discrete phylogroup of the family Diplostomidae. The life history of N. americanum is unknown and currently limited to the description of the adult stage in avian hosts. The molecular data generated in this study offer insight into the phylogenetic placement of N. americanum within the Diplostomatidae and will aid in identifying different life stages in putative intermediate hosts.

LOW PREVALENCE OF WEST NILE VIRUS ANTIBODIES IN SELECT NORTHERN CALIFORNIA OWL SPECIES (2007-2014).

The objective of this study was to determine evidence of previous West Nile virus (WNV) infection in northern California owls. Owl serum samples were collected from birds presenting to a veterinary medical teaching hospital between 2007 and 2014 and were screened for the presence of WNV antibodies by an indirect enzyme immunoassay (EIA). Only one of 71 samples (1.41%) tested was positive by EIA and confirmed by a plaque reduction neutralization test; it was the most recent sample collected. The reason for the low prevalence of WNV in these California owls despite a high prevalence in sympatric avian species in the same region is unknown and should be a topic for further research.

Infecção por pox vírus e Aspergillus fumigatus em Bubo virginianus (Coruja jacurutu) / Avipoxvirus infecction in Bubo virginianus (great horned owl)

Este trabalho descreve um caso de infecção mista por pox vírus e Aspergillus fumigatus em Bubo virginianus (coruja jacurutu). A ave, um macho adulto, foi encaminhada ao Núcleo de Reabilitação da Fauna Silvestre do Instituto de Biologia da Universidade Federal de Pelotas (NURFS/CETAS/UFPEL). Apresentava bom estado corporal, estava ativa, porém com incapacidade de voo. Após três dias apresentou lesões crostosas e de aspecto verrucoso na superfície dorsal das patas. Havia, também, nódulos de mesmo aspecto na pálpebra esquerda e na cera. A ave morreu após 15 dias de sua chegada ao NURFS e foi necropsiada no Laboratório Regional de Diagnóstico da Faculdade de Veterinária da Universidade Federal de Pelotas (LRD/UFPel). Histologicamente, as lesões verrucosas caracterizavam-se por hiperplasia do epitélio e nas células das camadas basal, espinhosa, granular e córnea havia corpúsculos de inclusão intracitoplasmáticos do tipo Bollinger. Na microscopia eletrônica foram visualizadas partículas virais características de pox vírus, incluindo Bubo virginianus como um hospedeiro do vírus. Havia, ainda, infiltrado inflamatório de células mononucleares e focos de colônias bacterianas na derme. Nos pulmões havia congestão e presença de granulomas com hifas fúngicas, que pela técnica de Grocott, apresentaram ramificação dicotômica compatível com Aspergillus spp., identificado na cultura como A. fumigatus. O diagnóstico de infecção por avipoxvirus pode contribuir para estudos relacionados com a ocorrência desta doença nas populações de vida livre e como informação auxiliar para o manejo e conservação desta espécie. Sugere-se, ainda, a inclusão do uso de raios-X nos protocolos de centros de reabilitação como o diagnostico de aspergilose em aves rapinantes com bom estado corporal, porém incapazes de voar.(AU)

This paper describes a case of mixed infection by pox virus and Aspergillus fumigatus in Bubo virginianus (Owl Jacurutu). An adult male Bubo virginianus was referred to the Núcleo de Reabilitação da Fauna Silvestre, Instituto de Biologia, Universidade Federal de Pelotas (NURFS/CETAS/UFPEL). The owl was active and had a good body condition but with flight disability. After three days of their admission at NURFS the owl developed crusty and verrucous lesions at the dorsal surface of their feet. Also it had nodes on the left eyelid and cera with the same aspect. The owl died 15 days after its arrival. Necropsy and histopatological examination were carried out. The warty lesions had hyperplasia of the epithelium and intracytoplasmic Bollinger-like inclusion bodies in the basal, spinal, granulosa layer and cornea. Viral particles characteristic of pox viruses were shown by electron microscopy. This case includes Bubo virginianus as a host of the avipoxvirus. There were also a mononuclear inflammatory cell infiltrate and bacterial colonies in the dermis. In the lugs, there was congestion and presence of granulomas with intralesional fungal hyphae. With the Grocott stain those structures showed dichotomous branching which was later identified in mycological culture as characteristic for A. fumigates. The diagnosis of avipoxvirus infection can contribute to studies related to the occurrence of this disease in free-living populations and as auxiliary information for the management and conservation of this raptor species. It is also suggested to include the use of X-rays in rehabilitation center protocols as screening test to diagnose aspergillosis in birds of prey with good body condition but inability to fly.(AU)

PHARMACOKINETIC PROPERTIES OF A SINGLE ADMINISTRATION OF ORAL GABAPENTIN IN THE GREAT HORNED OWL (BUBO VIRGINIANUS).

Gabapentin (1-[aminomethyl] cyclohexane acetic acid) is a γ-aminobutyric acid analogue that has been shown to be efficacious for neuropathic pain control in humans. Plasma gabapentin concentrations >2 µg/ml are considered effective in treating epilepsy in humans and are suggested to provide analgesia for neuropathic pain. This study investigated the pharmacokinetics of a single oral dose of gabapentin suspension (11 mg/kg) in great horned owls ( Bubo virginianus ). Plasma gabapentin concentrations were determined in six healthy birds for 48 hr using high-performance liquid chromatography with mass spectrometric detection. Plasma gabapentin concentrations were estimated by noncompartmental pharmacokinetic analysis. The harmonic mean (±SD) maximum concentration (Cmax), time to maximum concentration (Tmax), and elimination half-life (tv2λZ) for gabapentin (11 mg/kg) were 6.17±0.83 µg/ml, 51.43±5.66 min, and 264.60±69.35 min, respectively. In this study, plasma gabapentin concentrations were maintained above 2 µg/ml for 528 min (8.8 hr), suggesting that gabapentin administered orally every 8 hr may be appropriate in great horned owls.

Owl predation on snowshoe hares: consequences of antipredator behaviour.

We show evidence of differential predation on snowshoe hares (Lepus americanus) by great horned owls (Bubo virginianus) and ask whether predation mortality is related to antipredator behaviour in prey. We predicted higher predation on (1) young and inexperienced hares, (2) hares in open habitats lacking cover to protect from owl predation, and (3) hares in above average condition assuming that rich food patches are under highest risk of predation. Information on killed hares was obtained at nest sites of owls and by monitoring hares using radio-telemetry. The availability of age classes within the hare population was established from live-trapping and field data on reproduction and survival. Great horned owls preferred juvenile over adult hares. Juveniles were more vulnerable to owl predation before rather than after dispersal, suggesting that displacement or increased mobility were not causes for this increased mortality. Owls killed ratio-collared hares more often in open than in closed forest types, and they avoided or had less hunting success in habitats with dense shrub cover. Also, owls took hares in above average condition, although it is unclear whether samples from early spring are representative for other seasons. In conclusion, these results are consistent with the hypothesis that variation in antipredator behaviours of snowshoe hares leads to differential predation by great horned owls.