Owl Habitat Research Articles

Home ranges, habitat selection, and energy expenditure of Strix varia (Barred Owls): Understanding the full diel cycle matters for enhancing urban landscapes

Abstract We integrated GPS and accelerometer data to examine habitat selection and energy expenditure patterns across the diel cycle in Strix varia (Barred Owls), addressing a critical gap in wildlife research that often overlooks activity during the “inactive” phase. Owls in Baton Rouge, Louisiana, selected forests with tall canopies and open understories, particularly in affluent neighborhoods, supporting the “luxury effect” in urban biodiversity. Nocturnal home ranges were larger (31.8 ha) compared to diurnal home ranges (8.9 ha), indicating broader habitat use at night. The total area of preferred nocturnal habitat was 33% of the Baton Rouge study area, whereas preferred diurnal habitat comprised only 5%. Energy expenditure was inversely related to preference in nocturnal home ranges but increased with preference in diurnal home ranges. Our models were validated using independent data from Clemson, South Carolina, supporting the robustness of our analysis and revealing generalities in owl habitat selection across these regions. This research contributes to a deeper understanding of urban ecology, highlighting habitat components preferred by owls and possibly other forest-dwelling species. It emphasizes the difference in nocturnal and diurnal home range sizes, the scarcity of daytime refuges for S. varia in urban landscapes, and the variation in energy expenditure in preferred habitats. Our findings advocate for urban designs that accommodate wildlife activity throughout the day and night, and highlight the positive correlation between preferred owl habitat and affluent neighborhoods, underscoring the need for equitable distribution of green spaces to foster biodiversity across socioeconomic gradients. These insights will help develop strategies to enhance the ecological value of urban environments and the conservation of S. varia and associated forest-dwelling species in rapidly urbanizing areas.

Detection dogs can help researchers with elusive forest owl conservation

AbstractElusive fauna are often studied indirectly, via traces they leave behind, or via other non‐invasive survey methods. Critically endangered Tasmanian masked owls are both rare and elusive, which hampers conservation efforts. Spotlighting and call playback often have low success rates in accurately determining the presence/absence of Tasmanian masked owls. Using indirect survey techniques for traces such as owl pellets can be more efficient and provide a more reliable source of detailed data regarding presence/absence, diet, health, population structure and environmental contaminants. However, pellets can be difficult for researchers to find in the field. We evaluate whether detection dogs are effective in finding owl pellets in two steps: an experimental trial comparing the performance of a dog team to that of an ecologist with significant field experience with masked owls; and in a pilot field study where the dog team searched potential owl habitat in Tasmanian forests. During the experimental trials, the dog team significantly outperformed the ecologist. The dog team was more sensitive, finding 89% versus 40% of pellets present for the ecologist, and took half as long to search an equivalent‐sized search area. The combined efficiency of the dog team was 4.5 times greater than that of an ecologist working alone. During the pilot study, in searching areas of potential masked owl habitat, no pellets were found. However, when sites were visited where owls were known to have been recently sighted, the dog team were able to find large numbers of owl pellets suitable for collection and potential data extraction. Our trials suggest that dogs can find owl pellets with considerably greater sensitivity and efficiency than ecologists working alone and that they would be best used in combination with targeted surveys, especially when the detection and subsequent collection of as many pellets as possible is desirable for DNA extraction or other analysis.

Can environmental legislation protect a threatened apex predator across different land tenures?

Ecological impact assessments are undertaken in compliance with legislative mandates to evaluate the effects of proposed habitat modification. This task becomes complex when evaluating the impacts on highly mobile species like apex predators. Despite their importance to ecosystem function, environmental policies may inadequately protect apex predator habitat. Here we provide a case study that examines the efficacy of legislation and impact assessment tools in protecting habitat for a wide-ranging and threatened apex predator. The high resource requirements of apex predators, and their utilisation of large areas of high-quality habitat make them ideal conservation surrogates for other less resource demanding species, and as such good case studies in assessing the effectiveness of policy. The powerful owl (Ninox strenua) occurs across many landscape types throughout its distribution, including large tracts of private property and public landholdings, making this species difficult to assess through impact assessments. To examine the level of legislative protection for powerful owls, and how well their habitat use is captured, we compared GPS tracking data to environmental policy and industry impact assessment tools. We found that legislation has limited potential to protect powerful owl habitat and owls are likely dismissed from impact assessments due to their cryptic and wide-ranging behavioural traits. The existing legislative safeguards seem inadequate, and these shortcomings are likely contributing to species decline. There is a critical need for policy to be applicable to both public and private land tenure, and for legislation and impact assessment tools to incorporate research data for effective conservation and management.

What We Owe Owls. Nonideal Relationality among Fellow Creatures in the Old Growth Forest

Though many of us have constructed our lives (or have had them constructed for us) such that it is easy to ignore or forget, human lives are entangled with other animals in many ways. Some interspecies relations would arguably exist in some form or another even under an ideal model of animal ethics. Others have an inescapably non-ideal character – these relationships exist as they do because things have gone wrong. In such circumstances we have reparative duties to animals we have wronged because we have wronged them. Here I draw upon Christine Korsgaard’s “Fellow Creatures” (2018) and other nonideal approaches to animal ethics to critically assess the United States Fish & Wildlife Service practice of killing barred owls to protect endangered spotted owls in the old growth forest of the Pacific Northwest. This is a difficult case to be sure, but one that can benefit from non-ideal moral assessment in terms of interspecies relational repair. I argue for increased spotted owl habitat preservation and forest restoration as an alternative to barred owl removal that better aligns with both nonideal relational animal ethics and stated US Fish & Wildlife Service values.

Spatial and temporal dynamics of Mexican spotted owl habitat in the southwestern US

ContextUnderstanding habitat dynamics is essential for effective conservation as landscapes rapidly change. In a companion paper in this issue, Shirk et al. (2023) introduced an automated habitat monitoring system using Google Earth Engine and applied this framework to develop a dynamic model of Mexican spotted owl (Strix occidentalis lucida) habitat across the southwestern US from 1986 to 2020.ObjectivesWe explored the application of this dynamic model of Mexican spotted owl habitat in the context of the species’ ecology.MethodsWe evaluated environmental correlates of Mexican spotted owl habitat, assessed potential spatial non-stationarity in habitat selection, estimated long-term trends in habitat by quantifying changes in habitat amount and quality between 1986 and 2020, and evaluated the extent to which habitat changes over the past 35 years have been driven by wildfire.ResultsTopography and climate appeared to outweigh reflectance-based (vegetation) metrics in describing Mexican spotted owl habitat and habitat selection was non-stationary across modeling sub-regions. Total habitat area for Mexican spotted owls declined by ~ 21% since 1986 (0.6% annually), but trends varied spatially and some even reversed over the past decade. Wildfire was responsible for between 8 and 35% of total habitat loss, depending on the sub-region considered.ConclusionsThe automated habitat monitoring system allowed trend estimation and accurate assessment of current habitat status for Mexican spotted owls; maps were accurate, spatially detailed, and current. The ability to continually produce accurate maps for large land areas for threatened species such as the Mexican spotted owl facilitates science-based land management on public lands in the southwestern US.

Studi Populasi dan Karakteristik Pohon Bertengger Celepuk Rinjani (Otus jolandae) di Beberapa Jalur Hutan Kemasyarakatan (HKM) Wanalestari Desa Karang Sidemen Kabupaten Lombok Tengah

Rinjani Scops Owl (Otus Jolandae) is an endemic fauna that is included in the family of owls that are found in several forests that have been in the boundary or in the ecosystem of Mount Rinjani. The latest report published by IUCN in 2016 on the Rinjani Scops Owl (Otus Jolandae) is included in the Near Threatened (almost threatened) category. The purpose of this research is to know the population and characteristics of the trees perched Rinjani Scops Owl (Otus Jolandae) in several public forest lines Wanalestari Karang Sidemen village, Central Lombok. The method used in this research is divided into preliminary studies and primary research, where preliminary studies have been a method of literary studies, interviews, and observations. Then the main research has the IPA (Index Point Of Ambudance) method, measurement Of environmental physical condition, and vegetation structure with single compartments. Analysis of the user data is quantitative and qualitative. Results showed that the total population of Rinjani Scops Owl (Otus Jolandae) across the observation line in Hkm Wanalestari amounted to 16 individuals with an density of population each between 0,76-1,27 ha. The tree of the perched Rinjani Scops Owl (Otus Jolandae) consists of six types, namely the Dadap (Erythrina variegata) tree, Jackfruit (Artocarpus Heterophyllius), Durian (Durio zibethinus), Pecan (Aleurites moluccanus), Randu (Ceiba pentandra) and avocado (Parsea americana). The height of the Tengger tree ranges between 5-9 meters, diameter between 31,4-76,6 cm, and an area of heading 31,7-113,4 m2. The average temperature of Rinjani Scops Owl (Otus Jolandae) habitat of 25.4-25.6 °C humidity 76,4-76,6% and light intensity ranged from 0.9-4.68 Lux.
 Key Words : Rinjani Scops Owl, Animals, Population, Characteristics of perched trees

Short-Eared Owl Land-Use Associations during the Breeding Season in the Western United States

ABSTRACT The Short-eared Owl (Asio flammeus) is a species of conservation concern in the western USA, with evidence for declining population sizes. Monitoring of Short-eared Owls is complicated because of their low site fidelity and nomadic movements. We recruited community-science participants to implement a multi-year survey of Short-eared Owls across eight states in the western USA, resulting in a program of sufficient temporal and spatial dimensions to overcome many of the challenges in monitoring this species. We implemented both multi-scale occupancy and colonization/extinction modeling to provide insights into land-cover use, and to identify which cover types supported higher occurrence. Short-eared Owls were associated with native and anthropogenic land-cover types, but site occupancy varied among these categories and at different scales. Native grasslands, marsh/riparian, hay/fallow agriculture, and cultivated croplands were occupied most consistently across years. Occupancy rates differed at different scales (e.g., marsh/riparian was the only land-cover type positively associated with occupancy at both transect and point scales). Contrary to expectations, native shrubland was negatively associated with occupancy at the point scale, and exhibited low colonization and high extinction rates. Our results suggest that conserving native landscapes in general, and grasslands, marsh, and riparian areas specifically, would benefit Short-eared Owls. Furthermore, Short-eared Owl occupancy was positively associated with hay/fallow land-cover types, suggesting that some nonnative land-cover types can function as Short-eared Owl habitat. Lastly, our results highlight how developing a broad-scale community science survey can inform conservation for a species not well monitored by existing survey programs.

Forest restoration limits megafires and supports species conservation under climate change

Climate change and fire suppression have altered disturbance regimes in forest ecosystems globally. In the seasonally dry forests of western North America, large‐scale restoration may reduce severe fire and increase forest resilience but also eliminate existing habitat for sensitive wildlife species. We modeled bioregional‐scale effects of forest restoration on future severe fire activity and occupancy dynamics of an old‐forest species declining in abundance, the spotted owl (Strix occidentalis), in the Sierra Nevada mountains of California. Our findings suggest restoring historical forest structure may mitigate severe fire activity as the climate warms, particularly when restoration occurs in owl habitat. On average, benefits provided by restoration to owls (reduced severe fire) were found to exceed potential costs (direct habitat alteration) by mid‐century. However, the magnitude and direction of restoration trade‐offs varied spatially, which informs restoration planning. When large, old trees are maintained, forest restoration can provide co‐benefits to old‐forest species and forest ecosystem resilience under climate change.

Habitat selection by a predator of rodent pests is resilient to wildfire in a vineyard agroecosystem.

Conservation of uncultivated habitats can increase the potential for ecosystem services in agroecosystems, but these lands are also susceptible to wildfires in the arid western United States. In Napa Valley, California, abundant rodent pests and an interest in integrated pest management have led wine producers to use nest boxes to attract Barn Owls (Tyto furcata) to winegrape vineyards. The viability of this practice as a method to control rodent pests depends heavily on the amount of hunting effort that Barn Owls expend in vineyards, which is known to be influenced by the amount of uncultivated land cover types surrounding the nest box. Wildfires burned nearly 60,000 ha of mainly urban and uncultivated lands surrounding Napa Valley in 2017, altering Barn Owl habitats. We compared GPS tracking data from 32 Barn Owls nesting in 24 individual nest boxes before and after the fires to analyze their hunting habitat selection. Owls with burned areas available to them after the fires had home ranges that shifted toward the fires, but selection was not strongly associated with burned areas. Though there was some spatial use of burned areas, selection of land cover types was similar for birds before and after the fires and in burned and unburned areas. The strongest selection was for areas closest to the nest box, and most recorded locations were in grassland, though selection indicated that owls used land cover types in proportion to their availability. Overall, habitat selection was resilient to changes caused by wildfires. These results are important for farmers who use nest boxes as a means of rodent control, which may be affected after dramatic disturbance events, especially as wildfires increase in the western United States.

Is “Fuel Reduction” Justified as Fire Management in Spotted Owl Habitat?

The California Spotted Owl is an imperiled species that selects mature conifer forests for nesting and roosting while actively foraging in the “snag forest habitat” created when fire or drought kills most of the trees in patches. Federal agencies believe there are excess surface fuels in both of these habitat conditions in many of California’s forests due to fuel accumulation from decades of fire suppression and recent drought-related tree mortality. Accordingly, agencies such as the U.S. Forest Service are implementing widespread logging in Spotted Owl territories. While they acknowledge habitat degradation from such logging, and risks to the conservation of declining Spotted Owl populations, agencies hypothesize that such active forest management equates to effective fuel reduction that is needed to curb fire severity for the overall benefit of this at-risk species. In an initial investigation, I analyzed this issue in a large 2020 fire, the Creek Fire (153,738 ha), in the southern Sierra Nevada mountains of California. I found that pre-fire snag density was not correlated with burn severity. I also found that more intensive forest management was correlated to higher fire severity. My results suggest the fuel reduction approach is not justified and provide indirect evidence that such management represents a threat to Spotted Owls.

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.

Labor market impacts of land protection: The Northern Spotted Owl

Environmental policies often draw criticism due to their potential impacts on labor market outcomes. Previous work has studied sector-specific impacts following air quality regulations, or examined overall employment effects of land-use policies. In the case of the protection of the Northern Spotted Owl under the Endangered Species Act in 1990, millions of acres of highly productive federal timberland in the Pacific Northwest and northern California were set aside. Concerns regarding declining employment in the timber industry following the listing are often mentioned as a cautionary tale regarding future listings under the Act. However, disentangling the policy impact from other economic factors affecting employment such as recessions and sector-specific trends is challenging. We use a range of control groups to estimate the impact of the 1990 listing of the Northern Spotted Owl had on labor market outcomes in the Lumber and Wood Products sector. Our set of main results indicate long-run declines in timber industry employment of 13.9% using a regional perspective, 28.1% using a national perspective, and a 9.5% decline in the number of establishments. In the owl habitat range there were 114,600 timber employees in the pre-treatment period; about 1.4% of total employment in those counties. In terms of jobs, the declines represent around 16,000 or 32,000 timber jobs within the Pacific Northwest and northern California. We find heterogeneous effects with areas having larger shares of protected federal timberland experiencing larger declines in employment. Our findings indicate land protection policies may pose significant employment impacts to land-reliant industries.

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.

Behaviour-specific habitat selection patterns of breeding barn owls

BackgroundThe intensification of agricultural practices over the twentieth century led to a cascade of detrimental effects on ecosystems. In Europe, agri-environment schemes (AES) have since been adopted to counter the decrease in farmland biodiversity, with the promotion of extensive habitats such as wildflower strips and extensive meadows. Despite having beneficial effects documented for multiple taxa, their profitability for top farmland predators, like raptors, is still debated. Such species with high movement capabilities have large home ranges with fluctuation in habitat use depending on specific needs.MethodsUsing GPS devices, we recorded positions for 134 barn owls (Tyto alba) breeding in Swiss farmland and distinguished three main behavioural modes with the Expectation-Maximization binary Clustering (EMbC) method: perching, hunting and commuting. We described barn owl habitat use at different levels during the breeding season by combining step and path selection functions. In particular, we examined the association between behavioural modes and habitat type, with special consideration for AES habitat structures.ResultsDespite a preference for the most common habitats at the home range level, behaviour-specific analyses revealed more specific habitat use depending on the behavioural mode. During the day, owls roosted almost exclusively in buildings, while pastures, meadows and forest edges were preferred as nocturnal perching sites. For hunting, barn owls preferentially used AES habitat structures though without neglecting more intensively exploited areas. For commuting, open habitats were preferred over wooded areas.ConclusionsThe behaviour-specific approach used here provides a comprehensive breakdown of barn owl habitat selection during the reproductive season and highlights its importance to understand complex animal habitat preferences. Our results highlight the importance of AES in restoring and maintaining functional trophic chains in farmland.

Integrating forest restoration, adaptation, and proactive fire management: Rogue River Basin case study

Uncharacteristic disturbances exacerbated by climate change are challenging forests and social systems of North America. To improve efficiency and effectiveness of forest management to address these challenges, we demonstrated structured decision-making in the collaborative development of a novel 20-year dry forest management strategy for southwestern Oregon, USA. We framed priorities and evaluated options with a wildfire risk assessment, then modeled stand-scale prescriptions to estimate management outputs (e.g., area treated, fuels reduced, and timber volume). We mapped landscape-scale objectives and used optimization software to prioritize treatment placement constrained by realistic access considerations and robust habitat protections. The resulting prioritization integrated proactive forest adaptation and fire management (ecological forest thinning, prescribed fire) with protection of imperiled species. To evaluate tradeoffs, we tested three 20-year scenarios, finding that the All-Lands scenario best mitigated wildfire risk; it reduced risk overall by 70%, to homes by 50%, and to core northern spotted owl habitat by 47%. This scenario treated 25% of the 1.9 million ha landscape, including 31% of federal land and 40% of the community at risk. Clear articulation of collaborative objectives and evaluation of scenarios have expanded partnerships and co-investment in actions supporting a shared vision of resilient southwestern Oregon forests applicable to other landscapes.

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 >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.

Agriculture creates subtle genetic structure among migratory and nonmigratory populations of burrowing owls throughout North America.

Population structure across a species distribution primarily reflects historical, ecological, and evolutionary processes. However, large‐scale contemporaneous changes in land use have the potential to create changes in habitat quality and thereby cause changes in gene flow, population structure, and distributions. As such, land‐use changes in one portion of a species range may explain declines in other portions of their range. For example, many burrowing owl populations have declined or become extirpated near the northern edge of the species' breeding distribution during the second half of the 20th century. In the same period, large extensions of thornscrub were converted to irrigated agriculture in northwestern Mexico. These irrigated areas may now support the highest densities of burrowing owls in North America. We tested the hypothesis that burrowing owls that colonized this recently created owl habitat in northwestern Mexico originated from declining migratory populations from the northern portion of the species' range (migration‐driven breeding dispersal whereby long‐distance migrants from Canada and the United States became year‐round residents in the newly created irrigated agriculture areas in Mexico). We used 10 novel microsatellite markers to genotype 1,560 owls from 36 study locations in Canada, Mexico, and the United States. We found that burrowing owl populations are practically panmictic throughout the entire North American breeding range. However, an analysis of molecular variance provided some evidence that burrowing owl populations in northwestern Mexico and Canada together are more genetically differentiated from the rest of the populations in the breeding range, lending some support to our migration‐driven breeding dispersal hypothesis. We found evidence of subtle genetic differentiation associated with irrigated agricultural areas in southern Sonora and Sinaloa in northwestern Mexico. Our results suggest that land use can produce location‐specific population dynamics leading to subtle genetic structure even in the absence of dispersal barriers.

California spotted owl habitat selection in a fire-managed landscape suggests conservation benefit of restoring historical fire regimes

Wildland fire is a disturbance that shapes frequent-fire forest ecosystems and the life-histories of wildlife species that inhabit them. The California spotted owl (Strix occidentalis occidentalis) is an iconic old-forest species that evolved under a frequent-fire regime in western North America. While recent studies have focused on owl response to large, severe fire events, relatively little is known about how owls might respond to prescribed fires and wildfires managed for resource benefit. Therefore, understanding how owls use landscapes that are managed using fire may offer insight into how owls respond to fire management. We studied the breeding season nocturnal foraging habitat selection of 22 GPS-tagged California spotted owls in three national parks (Yosemite, Sequoia, and Kings Canyon) in the Sierra Nevada, California, USA where natural fires have largely been allowed to burn during the past 50 years and controlled burning has been used to target additional areas. Consistent with other studies of this species, owls selected forests dominated by medium and large trees and avoided areas with smaller trees within their home ranges based on step selection analysis. Owls neither selected nor avoided forests burned by low- and moderate-severity, or high-severity fires, yet avoided larger patches of severely-burned forest (odds of selection decreased by 20% for every 10 ha increase in severely-burned patch area). These results indicated the importance of patch characteristics, suggesting that larger patches reflected either lower quality foraging habitat or increased predation risk, even in these frequent-fire landscapes where “large” severely-burned patches were small compared to those common after megafires. Additionally, selection strength increased for areas burned recently by lower-severity fire and, to a lesser extent, by older fires (largely of lower severity) as the extent of these burned areas increased within individual home ranges. These results suggested that lower-severity fire benefitted spotted owls and that these benefits declined over time. Thus, our findings are consistent with the hypothesis that California spotted owls are adapted to historical frequent-fire regimes of overall lower-severity with small high-severity patches. We hypothesize that fire management, coupled with medium- and large-tree retention, likely maintains high quality spotted owl habitat and may contribute to the observed owl population stability in Sequoia and Kings Canyon National Parks, compared to declining populations on three national forests. Finally, our results indicated that fire management, as practiced in these national parks, could benefit owl conservation elsewhere if challenges to the reintroduction of frequent-fire regimes can be overcome.

Annual climate in Mexican Spotted Owl habitat in the Sacramento Mountains, New Mexico: implications for responding to climate change

Annual climate in Mexican Spotted Owl habitat in the Sacramento Mountains, New Mexico: implications for responding to climate change

Mixed‐severity wildfire and habitat of an old‐forest obligate

AbstractThe frequency, extent, and severity of wildfire strongly influence the structure and function of ecosystems. Mixed‐severity fire regimes are the most complex and least understood fire regimes, and variability of fire severity can occur at fine spatial and temporal scales, depending on previous disturbance history, topography, fuel continuity, vegetation type, and weather. During high fire weather in 2013, a complex of mixed‐severity wildfires burned across multiple ownerships within the Klamath‐Siskiyou ecoregion of southwestern Oregon where northern spotted owl (Strix occidentalis caurina) demographics were studied since 1990. A year prior to these wildfires, high‐resolution, remotely sensed forest structural information derived from light detection and ranging (lidar) data was acquired for an area that fully covered the extent of these fires. To quantify wildfire impact on northern spotted owl nesting/roosting habitat, we fit a relative habitat suitability model based on pre‐fire locations used for nesting and roosting, and forest structure variables developed from 2012 lidar data. Our pre‐fire habitat suitability model predicted nesting/roosting locations well, and variable response functions followed known resource selection patterns. These forests had typical characteristics of old‐growth forest, with high density of large live trees, high canopy cover, and complex structure in canopy height. We projected the pre‐fire model onto lidar data collected two months post‐fire to produce a post‐fire suitability map, which indicated that >93% of pre‐fire habitat that burned at high severity was no longer suitable forest for nesting and roosting. We also quantified the probability that pre‐fire nesting/roosting habitat would burn at each severity class (unburned/low, low, moderate, high). Pre‐fire nesting/roosting habitat had lower probability of burning at moderate or high severity compared to other forest types under high burning conditions. Our results indicate that northern spotted owl habitat can buffer the negative effects of climate change by enhancing biodiversity and resistance to high‐severity fires, which are predicted to increase in frequency and extent with climate change. Within this region, protecting large blocks of old forests could be an integral component of management plans that successfully maintain variability of forests in this mixed‐ownership and mixed‐severity fire regime landscape and enhance conservation of many species.