APPARENT PREVALENCE, DIVERSITY, AND ASSOCIATED LESIONS OF PERIORBITAL NEMATODES IN A POPULATION OF BARRED OWLS (STRIX VARIA) FROM NORTHERN CALIFORNIA, USA.

Over the last four decades, Barred Owls (Strix varia) have expanded their range to include much of western North America, including California. This expansion is suspected to have contributed to declining populations of a closely related species, the federally threatened Northern Spotted Owl (Strix occidentalis caurina). As a result, understanding potential health threats to Barred Owls has implications for Spotted Owl health and recovery. From 2016 to 2020, 69 Barred Owls were collected to determine the apparent prevalence of periorbital nematode infection, to identify the parasite species present, and to investigate the potential pathologic effects on their hosts. The nematodes were morphologically identified as Oxyspirura and Aprocta spp. On the basis of phylogenetic analyses, they were clearly divergent from published sequences of other species within these genera. Overall, 34 (49%) Barred Owls were infected with periorbital nematodes, with Oxyspirura sp. infections being much more common (94%) than Aprocta sp. (18%). Histopathology revealed varying severity of conjunctivitis in infected owls. Despite the frequency of infection and subsequent inflammation, parasite burden was not associated with reduced body weight in these owls. As a result, the potential health effect of these nematodes is unclear. Further taxonomic characterization is needed to determine potential novelty of these nematodes.

Range-wide sources of variation in reproductive rates of northern spotted owls.

We conducted a range-wide investigation of the dynamics of site-level reproductive rate of northern spotted owls using survey data from 11 study areas across the subspecies geographic range collected during 1993-2018. Our analytical approach accounted for imperfect detection of owl pairs and misclassification of successful reproduction (i.e., at least one young fledged) and contributed further insights into northern spotted owl population ecology and dynamics. Both nondetection and state misclassification were important, especially because factors affecting these sources of error also affected focal ecological parameters. Annual probabilities of site occupancy were greatest at sites with successful reproduction in the previous year and lowest for sites not occupied by a pair in the previous year. Site-specific occupancy transition probabilities declined over time and were negatively affected by barred owl presence. Overall, the site-specific probability of successful reproduction showed substantial year-to-year fluctuations and was similar for occupied sites that did or did not experience successful reproduction the previous year. Site-specific probabilities for successful reproduction were very small for sites that were unoccupied the previous year. Barred owl presence negatively affected the probability of successful reproduction by northern spotted owls in Washington and California, as predicted, but the effect in Oregon was mixed. The proportions of sites occupied by northern spotted owl pairs showed steep, near-monotonic declines over the study period, with all study areas showing the lowest observed levels of occupancy to date. If trends continue it is likely that northern spotted owls will become extirpated throughout large portions of their range in the coming decades.

GAMOGONY OF SARCOCYSTIS STRIXI IN MAMMALIAN CELL CULTURES.

We are interested in the disease ecology of Sarcocystis species that infect birds of prey as definitive and intermediate hosts. The present study was done to test our hypothesis that a laboratory model can be developed for sarcocystis infection in mammals using gamma interferon gene knockout (KO) mice as a source of Sarcocystis strixi bradyzoites and mammalian cell cultures as a source of sporulated S. strixi oocysts. Sporocysts of S. strixi from a naturally infected barred owl (Strix varia) were fed to KO mice to produce sarcocysts, and the enclosed bradyzoites were obtained by acid-pepsin digestion of abdominal and thigh muscles. Bradyzoites, metrocytes, and an unusual spherical stage were seen in digest before the inoculation of host cells. The spherical stages stained dark with Giemsa stain, but no nucleus was observed, and they were seen free and associated with the concave portion of some bradyzoites. Examination of infected cell cultures demonstrated that macrogamonts and microgamonts were present at 24 hr post-inoculation. Since sporulated oocysts were not observed, we had to reject our current hypothesis.

Conspecific and congeneric interactions shape increasing rates of breeding dispersal of northern spotted owls.

Breeding dispersal, the movement from one breeding territory to another, is rare for philopatric species that evolved within relatively stable environments, such as the old-growth coniferous forests of the Pacific Northwest. Although dispersal is not inherently maladaptive, the consequences of increased dispersal on population dynamics in populations whose historical dispersal rates are low could be significant, particularly for a declining species. We examined rates and possible causes of breeding dispersal based on a sample of 4,118 northern spotted owls (Strix occidentalis caurina) monitored in seven study areas over 28 yr, 1990-2017, in Oregon and Washington, USA. Using a multistate mark-resight analysis, we investigated the potential impacts of an emergent congeneric competitor (barred owl Strix varia) and forest alteration (extrinsic factors), and social and individual conditions (intrinsic factors) on 408 successive and 1,372 nonsuccessive dispersal events between years. The annual probability of breeding dispersal increased for individual owls that had also dispersed in the previous year and decreased for owls on territories with historically high levels of reproduction. Intrinsic factors including pair status, prior reproductive success, and experience at a site, were also associated with breeding dispersal movements. The percent of monitored owls dispersing each year increased from ˜7% early in the study to ˜25% at the end of the study, which coincided with a rapid increase in numbers of invasive and competitively dominant barred owls. We suggest that the results presented here can inform spotted owl conservation efforts as we identify factors contributing to changing rates of demographic parameters including site fidelity and breeding dispersal. Our study further shows that increasing rates of breeding dispersal associated with population declines contribute to population instability and vulnerability of northern spotted owls to extinction, and the prognosis is unlikely to change unless active management interventions are undertaken.

Eimeria varia Upton, Campbell, Weigel & McKown, 1990 is a Junior Synonym of Eimeria megabubonis Upton, Campbell, Weigel & McKown, 1990.

AIM: The present work aims to morphologically and molecularly characterize an Eimeria sp. recovered from an adult, captive barred owl Strix varia in Mississippi, USA. While the owl was shedding oocysts, no clinical signs of coccidiosis were observed. MATERIALS AND METHODS: Oocysts collected from a barred owl, S. varia were isolated from feces by fecal flotation and characterized by light microscopy. The oocysts were allowed to sporulate in K2Cr2O7 for 7 days and measured for comparison with previously described Eimeria species. Genomic DNA was extracted from measured oocysts and the cytochrome c oxidase subunit 1 mitochondrial gene was amplified and sequenced for comparison and phylogenetic analyses with publicly available sequence data. RESULTS: Oocysts collected from S. varia were morphologically and molecularly consistent with all previous accounts of Eimeria megabubonis from the great horned owl Bubo virginianus and morphologically consistent with the only account of Eimeria varia from S. varia. Phylogenetic analyses grouped the E. megabubonis sequence from the present study with previously reported sequences from E. megabubonis. CONCLUSION: Morphological and molecular data from oocysts collected in this study reveal S. varia is a host for E. megabubonis. Agreement between current data, morphological and molecular data of E. megabubonis, and morphological data from the original description of E. varia indicates E. varia is a junior synonym of E. megabubonis.

Evaluation of Goniometry and Electrogoniometry of Carpus and Elbow Joints in the Barred Owl (Strix varia).

The motion of wing joints is a critical factor for successful flight in avian patients, but little information is available about goniometry in birds. Elbow and carpus joints in flexed and extended positions from 10 orthopedically normal wings of 6 adult wild barred owls (Strix varia) were evaluated with the animals under general anesthesia using a modified universal plastic goniometer and an electrogoniometer. These measurements were compared to those obtained using radiographic assessment. Intra- and interobserver reliability was calculated. Measurements in live animals were compared to those obtained from frozen-thawed carcasses. Results showed that the modified universal plastic goniometer can be used to obtain accurate results for elbow flexion and extension and for carpal flexion with good to excellent reliability compared to measurements collected from radiographic assessment. Measurements obtained using an electrogoniometer were less accurate and less reliable than those obtained with a plastic goniometer, possibly because of the size and configuration of the model used. Comparison of measurements from live animals and carcasses revealed no significant differences between mean measurements and suggested that further evaluation of carcasses as a model for study of goniometry measurements in avian wing joints should be considered.

Complete mitochondrial genome sequences of the northern spotted owl (Strix occidentalis caurina) and the barred owl (Strix varia; Aves: Strigiformes: Strigidae) confirm the presence of a duplicated control region.

We report here the successful assembly of the complete mitochondrial genomes of the northern spotted owl (Strix occidentalis caurina) and the barred owl (S. varia). We utilized sequence data from two sequencing methodologies, Illumina paired-end sequence data with insert lengths ranging from approximately 250 nucleotides (nt) to 9,600 nt and read lengths from 100-375 nt and Sanger-derived sequences. We employed multiple assemblers and alignment methods to generate the final assemblies. The circular genomes of S. o. caurina and S. varia are comprised of 19,948 nt and 18,975 nt, respectively. Both code for two rRNAs, twenty-two tRNAs, and thirteen polypeptides. They both have duplicated control region sequences with complex repeat structures. We were not able to assemble the control regions solely using Illumina paired-end sequence data. By fully spanning the control regions, Sanger-derived sequences enabled accurate and complete assembly of these mitochondrial genomes. These are the first complete mitochondrial genome sequences of owls (Aves: Strigiformes) possessing duplicated control regions. We searched the nuclear genome of S. o. caurina for copies of mitochondrial genes and found at least nine separate stretches of nuclear copies of gene sequences originating in the mitochondrial genome (Numts). The Numts ranged from 226-19,522 nt in length and included copies of all mitochondrial genes except tRNAPro , ND6, and tRNAGlu . Strix occidentalis caurina and S. varia exhibited an average of 10.74% (8.68% uncorrected p-distance) divergence across the non-tRNA mitochondrial genes.

Determination of Gastrointestinal Transit Times in Barred Owls ( Strix varia ) by Contrast Fluoroscopy.

Contrast imaging studies are routinely performed in avian patients when an underlying abnormality of the gastrointestinal (GI) tract is suspected. Fluoroscopy offers several advantages over traditional radiography and can be performed in conscious animals with minimal stress and restraint. Although birds of prey are commonly encountered as patients, little is known about GI transit times and contrast imaging studies in these species, especially owls. Owls are commonly encountered in zoological, educational, and wildlife settings. In this study, 12 adult barred owls ( Strix varia ) were gavage fed a 30% weight-by-volume barium suspension (25 mL/kg body weight). Fluoroscopic exposures were recorded at 5, 15, 30, 60, 120, 180, 240, and 300 minutes after administration. Overall GI transit time and transit times of various GI organs were recorded. Median (interquartile range [IQR]) overall GI transit time was 60 minutes (IQR: 19-60 minutes) and ranged from 5-120 minutes. Ventricular and small intestinal contrast filling was rapid. Ventricular emptying was complete by a median of 60 minutes (IQR: 30-120 minutes; range: 30-240 minutes), whereas small intestinal emptying was not complete in 9/12 birds by 300 minutes. Median small intestinal contraction rate was 15 per minute (IQR: 13-16 minutes; range: 10-19 minutes). Median overall GI transit time in barred owls is more rapid than mean transit times reported for psittacine birds and red-tailed hawks ( Buteo jamaicensis ). Fluoroscopy is a safe, suitable method for investigating GI motility and transit in this species.

The Effect of Manual Restraint on Physiological Parameters in Barred Owls ( Strix varia ).

Manual restraint is commonly necessary when working with avian species in medical, laboratory, and field settings. Despite their prevalence, little is known about the stress response in raptorial bird species. To further understand the effect of restraint on the stress response in birds of prey, 12 barred owls ( Strix varia ) were manually restrained for 15 minutes. Physiological parameters (cloacal temperature, respiratory rate, heart rate) were followed over time and recorded at defined points during the restraint period. Heart rate decreased significantly over the restraint period by a mean ± SD of -73 ± 46 beats/min. Respiratory rate also decreased significantly (median: -11 breaths/min, interquartile range: -8 to -18). Cloacal temperature increased significantly over time in manually restrained owls (median: +1.5°C [+2.7°F], interquartile range: 1.3°C-2.1°C [2.3°F-3.8°F]). This study is the first to document stress hyperthermia in an owl species. Similar to another raptorial bird, the red-tailed hawk ( Buteo jamaicensis ), both heart rate and respiratory rate decreased and cloacal temperature increased over time in restrained barred owls. Barred owls appear to cope differently to restraint stress when compared to psittacine species.

Dynamic N-occupancy models: estimating demographic rates and local abundance from detection-nondetection data.

Occupancy modeling is a widely used analytical technique for assessing species distributions and range dynamics. However, occupancy analyses frequently ignore variation in abundance of occupied sites, even though site abundances affect many of the parameters being estimated (e.g., extinction, colonization, detection probability). We introduce a new model ("dynamic N-occupancy") capable of providing accurate estimates of local abundance, population gains (reproduction/immigration), and apparent survival probabilities while accounting for imperfect detection using only detection/nondetection data. Our model utilizes heterogeneity in detection based on variations in site abundances to estimate latent demographic rates via a dynamic N-mixture modeling framework. We validate our model using simulations across a wide range of values and examine the data requirements, including the number of years and survey sites needed, for unbiased and precise estimation of parameters. We apply our model to estimate spatiotemporal heterogeneity in abundances of barred owls (Strix varia) within a recently invaded region in Oregon (USA). Estimates of apparent survival and population gains are consistent with those from a nearby radio-tracking study and elucidate how barred owl abundances have increased dramatically over time. The dynamic N-occupancy model greatly improves inferences on individual-level population processes from occupancy data by explicitly modeling the latent population structure.