Strix Occidentalis Research Articles

Distribution Modeling of Mexican Spotted Owl (Strix occidentalis lucida) in Mexico

ABSTRACT The Mexican Spotted Owl (Strix occidentalis lucida; hereafter spotted owl) is discontinuously distributed in the United States and Mexico. It is an understudied raptor and categorized as near threatened, with populations in rapid decline. Defining the distribution of the spotted owl can help delineate priority areas for monitoring and research. Using the Maxent algorithm, with seven climatic variables and 153 owl presence records, we generated the potential distribution of spotted owl in Mexico. Our distribution model had high predictive accuracy and defined potential areas in the Sierra Madre Occidental, Sierra Madre Oriental, and the Transverse Neovolcanic Belt. These areas were concentrated in the states of Durango, Zacatecas, Jalisco, Aguascalientes, and Chihuahua, as well as within four protected natural areas. Four weather variables contributed 81.8% to the model's prediction: mean diurnal temperature range (BIO 2, 33.5%), maximum temperature of the warmest month (BIO 5, 30.4%), mean temperature of the coldest quarter (BIO 11, 10.5%) and the amount of precipitation in the wettest month (BIO 13, 7.4%). We recommend population monitoring in areas of climatic suitability predicted by the model to improve knowledge about the status of the Mexican Spotted Owl.

Northern spotted owl nesting forests as fire refugia: a 30-year synthesis of large wildfires

BackgroundThe northern spotted owl (Strix occidentalis caurina) is an Endangered Species Act-listed subspecies that requires coniferous forests with structurally complex and closed-canopy old-growth characteristics for nesting. With climate change, large wildfires are expected to become more common within the subspecies’ range and an increasing threat to these types of forests. Understanding fire severity patterns related to suitable nesting forest will be important to inform forest management that affects conservation and recovery. We examined the relationship between fire severity and suitable nesting forest in 472 large wildfires (> 200 ha) that occurred in the northern spotted owl range during 1987–2017. We mapped fire severities (unburned-low, moderate, high) within each fire using relative differenced normalized burn ratios and quantified differences in severity between pre-fire suitable nesting forest (edge and interior) and non-nesting forest. We also quantified these relationships within areas of three fire regimes (low severity, very frequent; mixed severity, frequent; high severity, infrequent).ResultsAveraged over all fires, the interior nesting forest burned at lower severity than edge or non-nesting forest. These relationships were consistent within the low severity, very frequent, and mixed severity, frequent fire regime areas. All forest types burned at similar severity within the high severity, infrequent fire regime. During two of the most active wildfire years that also had the largest wildfires occurring in rare and extreme weather conditions, we found a bimodal distribution of fire severity in all forest types. In those years, a higher amount—and proportion—of all forest types burned at high severity. Over the 30-year study, we found a strong positive trend in the proportion of wildfires that burned at high severity in the non-nesting forests, but not in the suitable nesting forest types.ConclusionsUnder most wildfire conditions, the microclimate of interior patches of suitable nesting forests likely mitigated fire severity and thus functioned as fire refugia (i.e., burning at lower severity than the surrounding landscape). With changing climate, the future of interior forest as fire refugia is unknown, but trends suggest older forests can dampen the effect of increased wildfire activity and be an important component of landscapes with fire resiliency.

Conservation Letter: Raptors and Anticoagulant Rodenticides

Conservation Letter: Raptors and Anticoagulant Rodenticides

Dual Discounting in Renewable Resource Planning under Risk.

Renewable resource planning and management projects entail evaluating economic and ecological criteria in the long term. During the past decade or so, dual discounting--ecological criteria discounted at a smaller rate than that for economic criteria--has been proposed for such projects as an alternative to the prevailing single-discounting scheme, out of theoretical and empirical considerations. We focus on how to apply this principle in planning problems that involve a multitude of risk in the attendant biological-economic system. A stochastic dynamic programming framework is introduced which allows dual discounting rates and finds the optimal decisions (passively) adapting to changes in the system. Furthermore, we show how to evaluate the variances of the criteria in this framework. With a case study of managing public forestlands in the US Pacific Northwestern region for both timber return and habitat preservation for the northern spotted owl (Strix occidentalis caurina), we illustrate the impacts that the dual-discounting scheme has on the trade-off between conflicting management objectives, the optimal planning strategy, the temporal development of the portion of the forestlands suitable for owl habitats, as well as its steady-state expected value and standard deviation.

Distribution of trespass cannabis cultivation and its risk to sensitive forest predators in California and Southern Oregon.

Illegal cannabis cultivation on public lands has emerged as a major threat to wildlife in California and southern Oregon due to the rampant use of pesticides, habitat destruction, and water diversions associated with trespass grow sites. The spatial distribution of cultivation sites, and the factors influencing where they are placed, remain largely unknown due to covert siting practices and limited surveillance funding. We obtained cannabis grow-site locality data from law enforcement agencies and used them to model the potential distribution of cultivation sites in forested regions of California and southern Oregon using maximum entropy (MaxEnt) methods. We mapped the likely distribution of trespass cannabis cultivation sites and identified environmental variables influencing where growers establish their plots to better understand the cumulative impacts of trespass cannabis cultivation on wildlife. We overlaid the resulting grow-site risk maps with habitat distribution maps for three forest species of conservation concern: Pacific fisher (Pekania pennanti), Humboldt marten (Martes caurina humboldtensis), and northern spotted owl (Strix occidentalis caurina). Results indicate that cannabis cultivation is fairly predictably distributed on public lands in low to mid-elevation (~800-1600m) forests and on moderate slopes (~30-60%). Somewhat paradoxically, results also suggest that growers either preferred sites inside of recently disturbed vegetation (especially those burned 8-12 years prior to cultivation) or well outside (>500m) of recent disturbance, perhaps indicating avoidance of open edges. We ground-truthed the model by surveying randomly selected stream courses for cultivation site presence in subsets of the modeling region and found previously undiscovered sites mostly within areas with predicted high likelihood of grow-site occurrence. Moderate to high-likelihood areas of trespass cultivation overlapped with 40 to 48% of modeled habitats of the three sensitive species. For the endangered southern Sierra Nevada fisher population, moderate-high likelihood growing areas overlapped with over 37% of modeled fisher denning habitat and with 100% of annual female fisher home ranges (mean overlap = 48.0% + 27.0 SD; n = 134) in two intensively studied populations on the Sierra National Forest. Locating and reclaiming contaminated cannabis grow sites by removing all environmental contaminants should be a high priority for resource managers.

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.

High rates of anticoagulant rodenticide exposure in California Barred Owls are associated with the wildland–urban interface

Abstract Pesticide use is pervasive and the exposure of non-target wildlife has been well documented over the past half-century. Among pesticides, anticoagulant rodenticides (AR) have emerged as a particularly important threat in forests of the western United States, with exposure and mortality reported for several species of conservation concern. To further quantify this threat, we collected specimens of Barred Owls (Strix varia) and Barred Owl x Spotted Owl hybrids from the Klamath and Cascade Mountains and Sierra Nevada in California, USA to use as indicator species for environmental contamination with AR and to infer exposure of closely related and ecologically similar Northern and California Spotted Owls (S. occidentalis caurina, and S. o. occidentalis, respectively). We tested 115 Barred Owl and 12 Barred Owl x Spotted Owl hybrid livers for 8 AR compounds and found high rates of exposure (62%) across our study area, and greater than previous studies in the Pacific Northwest. In addition, we sampled 7 ovaries from 7 females and 100% tested positive for AR. Female Barred Owls were more likely than males to be exposed (78% and 50%, respectively). Unlike previous studies, we found no clear link between illegal cannabis cultivation and AR exposure. However, Barred Owls sampled in proximity to the wildland–urban interface (WUI) were more likely to be exposed to AR. Though the exact source (e.g., cannabis cultivation or application around human dwellings) and location are unknown, the association of AR exposure with the WUI was supported from GPS data from Barred Owls, Northern and California Spotted Owls, and hybrids using the WUI for foraging. The high rate of AR exposure in Barred Owls and hybrids provides mounting evidence of an additional stressor that ARs may pose to Spotted Owls—including the first evidence for California Spotted Owls—and fauna native to western forest ecosystems.

REALIZED ECOLOGICAL NICHE OF THE MEXICAN SPOTTED OWL (Strix occidentalis lucida) IN MEXICO

Objective: To characterize the realized niche of the Mexican spotted owl (Strix occidentalis lucida) and compare the environmental values it uses within the Mexican physiographic provinces.Design/methodology/approach: The environmental temperature variables (n =7), precipitation (n = 7) and elevation (n = 1) were extracted from 79 unique occurrences sites of S. o. lucida. These values were grouped by physiographic provinces: Sierra Madre Occidental (n = 59), Sierra Madre Oriental (n = 13) and Transversal Neovolcanic Belt (n = 6). The climate and elevation of these sites were described and compared via non-parametric Kruskal-Wallis and Bonferroni-Dunn tests (P ? 0.05).Results: The presences of the spotted owls were both, dispersed and focallydistributed, over the geographic space in Mexico. The temperature and elevation variables have similar characteristics in the assessed physiographic provinces. To be noted, the precipitation variables showed significant differences among sites.Limitations on study/implications: This study describes the environmental characteristics of the realized niche of the Mexican spotted owl; however, it isnecessary to investigate other habitat variables at a smaller scale. Findings/conclusions: The temperature and elevation environmentalcharacteristics of the ecological niche of the Mexican spotted owl was similar between physiographic provinces.

Invader removal triggers competitive release in a threatened avian predator

Changes in the distribution and abundance of invasive species can have far-reaching ecological consequences. Programs to control invaders are common but gauging the effectiveness of such programs using carefully controlled, large-scale field experiments is rare, especially at higher trophic levels. Experimental manipulations coupled with long-term demographic monitoring can reveal the mechanistic underpinnings of interspecific competition among apex predators and suggest mitigation options for invasive species. We used a large-scale before-after control-impact removal experiment to investigate the effects of an invasive competitor, the barred owl (Strix varia), on the population dynamics of an iconic old-forest native species, the northern spotted owl (Strix occidentalis caurina). Removal of barred owls had a strong, positive effect on survival of sympatric spotted owls and a weaker but positive effect on spotted owl dispersal and recruitment. After removals, the estimated mean annual rate of population change for spotted owls stabilized in areas with removals (0.2% decline per year), but continued to decline sharply in areas without removals (12.1% decline per year). The results demonstrated that the most substantial changes in population dynamics of northern spotted owls over the past two decades were associated with the invasion, population expansion, and subsequent removal of barred owls. Our study provides experimental evidence of the demographic consequences of competitive release, where a threatened avian predator was freed from restrictions imposed on its population dynamics with the removal of a competitively dominant invasive species.

Noisy neighbors and reticent residents: Distinguishing resident from non-resident individuals to improve passive acoustic monitoring

Passive acoustic monitoring (PAM) is an increasingly common method for studying populations of vocally active species. However, the detection of individuals not resident to a site may obfuscate inferences about occurrence and population change. Here, we provide a framework for distinguishing resident from non-resident individuals to estimate territory—rather than site—occupancy in PAM programs by leveraging datasets on vocal behavior and acoustic detections for spotted owls (Strix occidentalis) in the Sierra Nevada, California, USA. Based on acoustic/GPS tags, the extent over which individuals typically vocalized (the “vocal home range”) was small relative to space use, such that the likelihood of double counting resident territory-holders across multiple survey sites was low. However, comparing passive acoustic detections to known resident owl locations revealed that detections occurred at PAM survey sites known to be unoccupied, possibly because of the presence of non-territorial individuals. Strict thresholds that required acoustic detections over multiple survey periods successfully removed all detections of non-resident individuals but increased the probability of not detecting resident individuals. Conversely, relatively liberal thresholds that minimized the probability of missing resident individuals increased the probability of detecting non-residents. Thus, a tradeoff exists between error types, with optimal threshold criteria dependent on conservation objectives. Our study highlights the importance of examining patterns in individual vocal behavior and acoustic detections to minimize inferential errors in PAM. It also provides a generalizable framework that can be tailored according to specific conservation objectives to strengthen inferences from PAM as it becomes standard practice in conservation science.

Optimizing landscape‐scale monitoring programmes to detect the effects of megafires

AbstractAimBy virtue of their spatial extent, landscape‐scale monitoring programmes may be well‐suited to support before‐after/control‐impact (BACI) studies of major disturbances such as megafires, but they may only have a few affected sites, reducing statistical power. I tested whether a variety of hypothetical but logistically plausible survey designs could provide statistically powerful assessments of hypothetical but empirically based population responses to megafire.LocationSimulation focused on fire‐prone forests.MethodsI varied the number of affected sites, detection probability, baseline occupancy and species’ responses to fire to create 72 monitoring scenarios. I then simulated 10 years of site occupancy data in which a megafire or other disturbance occurred between years 5 and 6 (n = 500 iterations).ResultsStatistical power to correctly reject the null hypothesis of no population response to megafire was high (mean across all scenarios = 0.78), but power to identify the correct population response (e.g. post‐fire occupancy declined and then recovered) was low (mean = 0.29). Statistical power to not underestimate the effect of a megafire on site occupancy was fairly high (mean = 0.66), but power to accurately estimate site occupancy was low (mean = 0.25). Statistical power increased with the number of affected sites (i.e., sample size) and with the intensity of the focal species’ response to megafire. Case study simulations based on an existing acoustic monitoring programme in the Sierra Nevada, USA, indicate that it is likely to identify Spotted Owl and Black‐backed Woodpecker population responses to megafires. Researchers can use the included simulation tutorial to implement their own power analyses.Main conclusionsLandscape‐scale monitoring programmes can identify population changes following megafires, but cannot reliably produce nuanced results, especially with only five years of post‐fire data. Smaller‐bodied species, which could be studied at more sites, are likely to be better focal species for megafire BACI studies. Aggregating landscape‐scale studies’ sampling coverage across many fire footprints to study the overall effects of megafires—rather than the effects of individual fires—may be a more informative approach.

Transparency About Values and Assertions of Fact in Natural Resource Management

Worldwide, unsustainable use of nature threatens many ecosystems and the services they provide for a broad diversity of life, including humans. Yet, governments commonly claim that the best available science supports their policies governing extraction of natural resources. We confront this apparent paradox by assessing the complexity of the intersections among value judgments, fact claims, and scientifically verified facts. Science can only describe how nature works and predict the likely outcomes of our actions, whereas values influence which actions or objectives society ought to pursue. In the context of natural resource management, particularly of fisheries and wildlife, governments typically set population targets or use quotas. Although these are fundamentally value judgments about how much of a resource a group of people can extract, quotas are often justified as numerical guidance derived from abstracted, mathematical, or theoretical models of extraction. We confront such justifications by examining failures in transparency about value judgments, which may accompany unsupported assertions articulated as factual claims. We illustrate this with two examples. Our first case concerns protection and human use of habitats harboring the northern spotted owl (Strix occidentalis caurina), revealing how biologists and policy scholars have argued for divergent roles of scientists within policy debates, and how debates between scientists engaged in policy-relevant research reveal undisclosed value judgments about communication of science beyond its role as a source of description (observation, measurement, analysis, and inference). Our second case concerns protection and use of endangered gray wolves (Canis lupus) and shows how undisclosed value judgments distorted the science behind a government policy. Finally, we draw from the literature of multiple disciplines and wildlife systems to recommend several improvements to the standards of transparency in applied research in natural resource management. These recommendations will help to prevent value-based distortions of science that can result in unsustainable uses and eventual extinctions of populations. We describe methods for communicating about values that avoid commingling factual claims and discuss approaches to communicating science that do not perpetuate the misconception that science alone can dictate policy without consideration of values. Our remedies can improve transparency in both expert and public debate about preserving and using natural resources, and thereby help prevent non-human population declines worldwide.

Megafire causes persistent loss of an old‐forest species

AbstractClimate change and a long legacy of fire suppression are leading to an increased prevalence of ‘mega‐disturbances’ such as drought and wildfire in terrestrial ecosystems. Evidence for the immediate effects of these novel disturbances on wildlife is accumulating, but little information exists on longer term impacts to species and ecosystems. We studied the occurrence dynamics of an iconic old‐forest species, the spotted owl (Strix occidentalis), on a long‐term study area in the Sierra Nevada, CA, USA from 1989 to 2020 to evaluate their multi‐scale population response following a 2014 megafire (the ‘King’ Fire) that affected a portion of our study area. We found that extensive severe fire within spotted owl sites resulted in both immediate site abandonment and prolonged lack of re‐colonization by owls six years post‐fire. Sites that experienced high pyrodiversity – a mosaic of burn severities – were more likely to persist after the fire, but this effect was only apparent at finer spatial scales. A potentially confounding factor, post‐fire salvage logging, did not explain variability in the probability of either owls persisting at sites or sites becoming re‐colonized; effects could be attributed only to severe fire extent and pyrodiversity. Our study demonstrates the prolonged effects of severe fire on the occupancy of this forest‐dependent species, suggesting that forest restoration that reduces megafires could benefit spotted owls. Our work emphasizes that long‐term monitoring can offer surprising learning opportunities and provide unparalleled value for understanding and addressing emerging environmental concerns.

Pyrodiversity and biodiversity: A history, synthesis, and outlook

AbstractAimPyrodiversity is the spatial or temporal variability in fire effects across a landscape. Multiple ecological hypotheses, when applied to the context of post‐fire systems, suggest that high pyrodiversity will lead to high biodiversity. This resultant “pyrodiversity–biodiversity” hypothesis has grown popular but has received mixed support by recent empirical research. In this paper, we sought to review the existing pyrodiversity literature, appraise support for the pyrodiversity–biodiversity hypothesis, examine potential mechanisms underlying the hypothesis and identify outstanding questions about pyrodiversity and future research needs.LocationGlobal terrestrial ecosystems.MethodsWe performed a systematic literature review of research related to pyrodiversity and the pyrodiversity–biodiversity hypothesis. We also examined how two individual species with distinct relationships with fire (spotted owl Strix occidentalis and black‐backed woodpecker Picoides arcticus) respond to pyrodiversity as case studies to illustrate underlying mechanisms.ResultsWe identified 41 tests of the pyrodiversity–biodiversity hypothesis reported from 33 studies; 18 (44%) presented evidence in support of the pyrodiversity–biodiversity hypothesis, while 23 (56%) did not. Our literature review suggested that support for the pyrodiversity–biodiversity hypothesis varies considerably with no consistent patterns across taxonomic groups and ecosystem types. Studies examining the pyrodiversity–biodiversity hypothesis often define pyrodiversity in different ways, examine effects at different scales and are conducted in ecosystems with different natural fire regimes, baseline levels of biodiversity, and evolutionary histories. We suggest these factors independently and jointly have led to widely varying support for the pyrodiversity–biodiversity hypothesis.Main ConclusionsClarifying the pyrodiversity–biodiversity hypothesis will be facilitated by stronger development of the different potential mechanisms underlying pyrodiversity–biodiversity relationships, which can be aided by examining how individual species respond to pyrodiversity. Future research would benefit from a closer examination of the role of scale (e.g. scale dependence) in pyrodiversity–biodiversity relationships, standardization of pyrodiversity metrics, broad‐scale mapping of pyrodiversity, and macroecological study of pyrodiversity–biodiversity relationships.

Elevational gradients strongly mediate habitat selection patterns in a nocturnal predator

AbstractMountain ecosystems contain strong elevational gradients in climate and vegetation that shape species distributions and the structure of animal communities. Nevertheless, studies of habitat selection for individual species rarely account for such gradients that often result in species being managed uniformly across their range, which may not improve conservation as intended. Therefore, we characterized variation in nocturnal habitat selection by 18 GPS‐tagged California spotted owls (Strix occidentalis occidentalis) along a 1400‐m elevational gradient in the Sierra Nevada, California. We characterized three‐dimensional forest structure with light detection and ranging data that we used in mixed‐effects resource‐ and step‐selection analyses of owl habitat selection. At lower elevations, owls selected stands with shorter trees, sites closer to hard edges between tall forests and open areas, sites with less diversity in forest seral types and sites with more ridge and southwest aspects. In contrast, owls at higher elevations selected the opposite. Within public forests that had taller trees and within their home range core (45% kernel density estimate of GPS points) areas, owls selected forests with less and more canopy cover at low and high elevations, respectively. Outside of their core areas, owls selected areas with fewer and more tall trees at low and high elevations, respectively. These findings may be explained by elevational gradients in prey distribution and variation in owl diet because owls consume more woodrats (Neotoma spp; earlier seral species) at lower elevations and more flying squirrels (Glaucomys sabrinus; older forest species) at higher elevations. Thus, at low elevations and in areas unlikely to support nesting, spotted owls could benefit from management that promotes woodrat habitat by encouraging oak regeneration and creating small brushy openings within forests with shorter (younger) trees. Conversely, at higher elevations, (1) enhancing flying squirrel habitat by promoting large trees and denser canopy on mesic sites and (2) managing for greater cover type diversity on southwest‐facing slopes and ridgetops is more likely to improve foraging habitat quality for spotted owls. The patterns of owl selection over elevational gradients has not been explicitly considered in most habitat management plans but clearly would improve management throughout mountain ecosystems.

Disentangling Post-Fire Logging and High-Severity Fire Effects for Spotted Owls

The Spotted Owl is a rare and declining raptor inhabiting low/middle-elevation forests of the Pacific Northwest, California, and the Southwest in the USA. It is well established that Spotted Owls select dense, mature, or old forests for nesting and roosting. High-severity fire transforms such forests into a unique forest type known as “snag forest habitat”, which the owls select for foraging. This habitat is disproportionately targeted by post-fire logging projects. Numerous recent articles have explored the influence of high-severity fire and post-fire logging on this species. Studies have shown that post-fire logging significantly reduces Spotted Owl occupancy, but efforts have generally not been made to disentangle the effects of such logging from the influence of high-severity fire alone on Spotted Owls. We conducted an assessment of published, peer-reviewed articles reporting adverse impacts of high-severity fire on Spotted Owls, exploring the extent to which there may have been confounding factors, such as post-fire logging. We found that articles reporting adverse impacts of high-severity fire on Spotted Owls were pervasively confounded by post-fire logging, and in some cases by a methodological bias. Our results indicate a need to approach analyses of high-severity fire and Spotted Owls differently in future research.

Genomic Variation and Recent Population Histories of Spotted (Strix occidentalis) and Barred (Strix varia) Owls.

Spotted owls (SOs, Strix occidentalis) are a flagship species inhabiting old-growth forests in western North America. In recent decades, their populations have declined due to ongoing reductions in suitable habitat caused by logging, wildfires, and competition with the congeneric barred owl (BO, Strix varia). The northern spotted owl (S. o. caurina) has been listed as “threatened” under the Endangered Species Act since 1990. Here, we use an updated SO genome assembly along with 51 high-coverage whole-genome sequences to examine population structure, hybridization, and recent changes in population size in SO and BO. We found that potential hybrids identified from intermediate plumage morphology were a mixture of pure BO, F1 hybrids, and F1 × BO backcrosses. Also, although SO underwent a population bottleneck around the time of the Pleistocene–Holocene transition, their population sizes rebounded and show no evidence of any historical (i.e., 100–10,000 years ago) population decline. This suggests that the current decrease in SO abundance is due to events in the past century. Finally, we estimate that western and eastern BOs have been genetically separated for thousands of years, instead of the previously assumed recent (i.e., <150 years) divergence. Although this result is surprising, it is unclear where the ancestors of western BO lived after the separation. In particular, although BO may have colonized western North America much earlier than the first recorded observations, it is also possible that the estimated divergence time reflects unsampled BO population structure within central or eastern North America.

Illuminating the Nocturnal Habits of Owls with Emerging Tagging Technologies

ABSTRACTOwls play important cultural, ecological, and indicator roles throughout the world. Yet owls’ cryptic behavior has led to uncertainties about their basic ecology, including foraging, communication, and functional roles within the community, and potentially hindered the implementation of effective conservation measures. Here we demonstrate the potential for next‐generation GPS tags capable of recording high‐precision, minute‐by‐minute locations paired with other technologies to resolve some of these uncertainties. We combined high‐precision GPS tagging data with infrared (IR) video recorded by arboreally‐mounted cameras at 5 spotted owl (Strix occidentalis) nest sites in the Sierra Nevada, USA to provide a uniquely detailed examination of owl foraging patterns. Our approach allowed us to identify the precise time and location of 54 predation events and prey identity. We also used high‐precision GPS tags with on‐board audio recorders to map the vocal activity of 8 individuals by matching the time of vocalizations in the audio data to GPS locations recorded at one‐minute intervals. The combined spatial and acoustic data revealed that nonbreeding males had the most widespread territorial vocal activity (i.e., producing 4‐note territorial calls), while females provisioning fledglings displayed extensive nonterritorial vocal activity (i.e., producing many contact calls). Thus, the GPS‐tag technologies we employed can provide opportunities to better understand owl foraging, communication, territoriality, and population dynamics. The methods we describe are time‐ and resource‐intensive but can be paired with techniques that are more applicable at landscape scales, such as stable isotope analyses, LiDAR‐based habitat analyses, and passive acoustic monitoring to link local processes to broad‐scale ecological patterns. Therefore, our approach could be applied to many species whose behavior inhibits direct observation. © 2021 The Wildlife Society.

Impacts of Postfire Management Are Unjustified in Spotted Owl Habitat

In mixed-conifer forests inhabited by California spotted owls, land managers hypothesize that without human intervention natural conifer regeneration will take many decades or longer to begin within interior areas of large high-severity fire patches, due to long distances from live tree seed sources. As a result, widespread post-fire logging, followed by sprayed application of herbicides and planting of conifer seedlings, are used to create tree plantations. These are activities routinely conducted in spotted owl territories following fires, despite current data that indicate this approach has adverse impacts on spotted owl occupancy. Land managers acknowledge such impacts, but continue these forest management practices, assuming they are a necessary harm, one that is warranted to ensure the later return of mature conifer forests used by spotted owls for nesting and roosting. However, few data have been gathered to test this hypothesis. At 5 years post-fire, we surveyed field plots on a grid within large high-severity fire patches in spotted owl habitat within the Rim fire of 2013 in the Sierra Nevada, California. In our analysis the percentage of plots lacking conifer regeneration decreased significantly with larger plot sizes, a finding contrary to previous studies which assumed vast “deforested” areas in wildland fires, a bias created by small plot size. We found higher conifer regeneration closer to live-tree edges, but we consistently found natural post-fire conifer regeneration at all distances into interior spaces of large high-severity fire patches, including &amp;gt;300 m from the nearest live trees. Distance from live-tree edges did not affect pine dominance in post-fire regeneration. The post-fire natural conifer regeneration reported in our results suggests that the adverse effects of current post-fire management in spotted owl habitat are not necessary practices that can be justified.

Invited Commentary: When a Conservation Conflict Comes Full Circle—The Spotted Owl Conflict is a Wicked Problem

The conservation of the Spotted Owl (Strix occidentalis) has been the center of a 40-yr conflict between those who wish to conserve owls and old growth forests and those who wish to log trees as commodities. Although the Spotted Owl conflict seems unique because it has lasted so long, it is no different than many other conservation conflicts in which many scientists—and raptor biologists specifically—might find themselves engaged. Therefore, I explore the commonality among conflicts, including specific details of the Spotted Owl case, to illustrate the problems inherent in conservation conflicts and why these disputes last so long. I suggest two general motivations that I believe capture the reasons behind people's willingness to engage in conflict: money and passion. Yet the specific motivations (e.g., economic well-being and ideology) nested within these general motivations are complex and interconnected. This complexity can lead to intractable situations, such as Spotted Owl conservation, which have been defined as “wicked problems” that cannot be resolved to the satisfaction of most. But understanding these broad motivations and identifying the wide variety of specific motivations nested within them may yield opportunities to manage—rather than resolve—a conservation conflict. Accordingly, I present a conceptual overview of the owl situation as a case study, along with some guidelines for raptor biologists working in conflict environments.