Intensifying disturbances such as high-severity wildfire and prolonged drought-related tree mortality - along with forest management activities intended to curb these disturbances - are reshaping wildlife habitat. As a result, older forest-dependent species are being affected in fire-prone forests. Yet, mapping these dynamic processes at fine spatial resolution across broad spatiotemporal scales remains challenging. Using 37 years (1986-2022) of California spotted owl (Strix occidentalis occidentalis) detection data from Southern California - the subspecies' southern range limit - we integrated a recently developed statewide fuels management database and remotely-sensed data with random forest models to (1) map annual habitat changes at 30-m resolution, and (2) attribute those changes to major disturbance types. Our analysis revealed that nesting/roosting habitat declined by 54 % since 1986, with 92 % of the remaining habitat concentrated in the San Bernardino National Forest. Prey acquisition habitat decreased by 40 % within this forest. Wildfire primarily drove nesting/roosting habitat loss, explaining 80 % of attributable declines post-2006, followed by drought/other (14 %) and fuels management (6 %). Potential territories with >= 48 ha of nesting/roosting habitat declined by 53 %, those with >= 48 ha of prey acquisition habitat declined by 47 %, and territories meeting both thresholds declined by 73 %. These results underscore dramatic habitat loss for spotted owls, highlight wildfire's disproportionate impact, and emphasize the San Bernardino National Forest's importance as a refuge. Limited nesting/roosting habitat declines from fuels management highlight its potential to reduce wildfire impacts on older forests. By integrating species distribution models with multi-disturbance mapping, our study offers a regional-scale framework that can be transferred to other species and ecosystems to monitor habitat dynamics and disturbance impacts.

Abstract Understanding drivers of habitat loss and fragmentation can inform conservation policy and action. However, drivers vary across space and time, and complete datasets of potential drivers that align with time series of species habitat are rare. We developed a 38‐year time‐series of nesting/roosting habitat for the California spotted owl in the Sierra Nevada, CA, USA, and used a novel disturbance dataset to attribute habitat changes to potential drivers. We found that the total area of high‐quality nesting/roosting habitat declined by 43% between 1985 and 2022. Moreover, the average high‐quality habitat patch became 68% smaller and 33% more isolated over the study period. During 2002–2022, drought was the most abundant disturbance in spotted owl habitat (49% of habitat affected), followed by high‐severity fire (32%) and fuels management (20%). However, the amount of disturbance did not always match impact. Drought, while most common, was responsible for only 20% of estimated habitat losses. High‐severity fire was responsible for nearly half (45%) of habitat loss, while fuels management was responsible for only 9% of habitat loss (and 14% of habitat gains). Dominant drivers of habitat loss varied spatially, suggesting the potential to use local information to calibrate conservation action. Previously, the absolute and relative impacts of fuels management, severe wildfires, drought, and other disturbance agents on spotted owl habitat were unknown. Here, we demonstrated that the most influential factor driving losses of high‐quality spotted owl habitat was high‐severity fire, and that fuels management, while associated with relatively smaller habitat losses, was also associated with habitat gains, suggesting net benefits of fuels management via its effect of reducing high‐severity fire. We demonstrate the power of using dynamic species distribution models to map and track habitat over time and understand the factors that may be contributing to observed habitat losses and gains.

Disturbances shape assemblages and spatial patterns of flora and fauna across the globe, with many disturbances increasing in severity and extent because of anthropogenic climate change and changes in land use. Accurate disturbance mapping and attribution can aid conservation science and decision-making in this era of rapid environmental change, but doing so remains challenging at fine resolutions and broad spatial scales. Here we demonstrate a novel approach for integrating remote sensing products with the US Forest Service's (USFS) Forest Activity Tracking System (FACTS) to map forest change and attribute those changes to wildfire, fuels management, and drought/other disturbance across 34,000 km2 of USFS lands in the Sierra Nevada and Southern California (2003-2022). We compared FACTS fuels management areas with annual remote sensing derived estimates of canopy loss (Mortality Magnitude Index (MMI) in the eDaRT system for Landsat processing) to develop FACTS querying filters that accounted for nearly all fuels management detected by eDaRT. We overlaid these data with fire severity (composite burn index) and drought/other (MMI) to attribute annual forest canopy change to these three primary disturbance agents and found 74 % of the area disturbed. Of the 25,000 km2 that experienced disturbance, wildfire dominated (69 %), followed by drought/other mortality (51 %), and fuels management (14 %; including prescribed fire), with overlap among categories. These results underscore recent widespread disturbance and the possible transformation of California forests and biodiversity. The accompanying disturbance dataset and code provide new and potentially powerful opportunities for scientists and managers studying and stewarding these rapidly changing ecosystems.

Climate and land-use change are dramatically altering the frequency, intensity, and extent of ecological disturbances, which threaten the persistence of at-risk species. To curb the pace and scale of disturbances, balance management and conservation priorities, and alleviate associated population declines, managers require high-quality information on species' responses to disturbance and their population trends across broad spatial scales that challenge the capacity of traditional, local-scale monitoring programs. Passive acoustic monitoring is a scalable approach to obtain occurrence data, but the extent to which it can be used to model occupancy dynamics and their environmental drivers remains uncertain. Here, we demonstrate how passive acoustic surveys can be analyzed within a Bayesian dynamic occupancy modeling framework to robustly estimate occupancy dynamics and responses to disturbance in the California spotted owl (Strix occidentalis occidentalis), which is threatened by increasingly large, severe "megafires." From 2021 to 2024, we collected ~2 million hours of audio from autonomous recording units deployed across seven national forests in the Sierra Nevada, California, USA. Spotted owls were less likely to initially occupy and colonize sites that were severely burned, and more likely to go locally extinct following high-severity fire. Further, we observed declining postfire occupancy trajectories, particularly when sites burned ≥50% high severity. Occupancy trends varied by national forest, but declined by 2% across the entire region. Our findings-which closely align with those from intensive, traditional demographic studies-demonstrate that large-scale passive acoustic monitoring paired with dynamic occupancy models can effectively detect species' responses to disturbance and estimate population trends, offering valuable insights for management across multiple spatial scales. Finally, we provide specific recommendations to help other passive acoustic monitoring programs successfully detect ecological responses to disturbance and track population changes.

ABSTRACT Controlling invasive species is a global conservation priority but is typically resource-limited, necessitating strategies to optimize control. Spatial prioritization methods can improve the efficiency of invader control by quantifying the benefits, costs, and risks of alternative intervention strategies. Yet prioritization designs are sensitive to the distinction between protecting native populations that are currently sympatric with invaders versus safeguarding presently allopatric native populations by preventing invader expansion. Gaining a better understanding of this distinction stands to improve our ability to prioritize the management of invaders whose distributions—and thus impacts on native species—are dynamic. We asked how prioritization designs addressing current versus future invader threats affected tradeoffs among focal species protection, biodiversity conservation, disturbance risk, and overlap with existing conservation infrastructure. As a case study, we spatially prioritized population control of invasive barred owls ( Strix varia ) in the northwestern US. We found that distinguishing between current versus future threats posed by barred owls to the native spotted owl ( S. occidentalis ) strongly mediated whether invader control stood to benefit native at-risk animal communities. Furthermore, this distinction also affected the degree to which population control would overlap with fire risk and federally protected forests, both of which plausibly affect the viability and success of conservation action. These results thus illustrate that deciding to prioritize the control of invaders based on their current versus future impacts on native species can dramatically affect the distribution and characteristics of high-priority areas for management. Our findings also directly inform control of barred owls in the northwestern US: we found that prioritizing future threats to spotted owls could protect at-risk amphibian communities from novel barred owl predation, but that high fire risk and minimal protected forest may complicate implementation. Thus, in both our system and more broadly, spatial prioritization methods are an important tool for quantitative, reproducible, and successful invader control.

Reducing fuel densities is the primary tool available to improve forest resilience to intensifying disturbance, but implementation is constrained by concern of effects to mature-forest associated species, such as spotted owls (Strix occidentalis). While the negative effects of severe fire on spotted owls are well studied, the influence of drought and fuels management on populations is uncertain, impeding fuels management. We integrated a novel dataset of California disturbance history with passive acoustic monitoring to compare the effects of severe fire, drought, and fuels management over 13 years on spotted owl occupancy across the Sierra Nevada, California, USA. Spotted owls were less likely to occupy 4 km(2) survey sites with a greater proportion of forest that burned at high severity and sites with a greater proportion of "heavier" fuels management (>25 % canopy reduction) but were insensitive to the proportion of "lighter" fuels management (<25 % canopy reduction) at sites. Across 7161 sites in the Sierra Nevada, severe fire resulted in an estimated loss of 482 occupied sites compared to only 65 lost from heavier treatments, owing to the limited implementation of fuels management in the region. Conversely, spotted owls were more likely to occur at sites containing a greater proportion of drought or other canopy reducing disturbance, presumably because of foraging opportunities facilitated by heterogenous forest conditions. Thus, recent severe fire has had a greater negative effect on spotted owls than fuels management, underscoring the potential benefits of increasing the pace and scale of fuels management for promoting both forest resilience and conserving mature-forest species.

Climate change and fire exclusion have changed disturbance regimes in forest ecosystems globally. In many seasonally dry forests, fuels management can mitigate severe wildfire behavior and create more resilient forests. Yet concern that fuels management might simplify forests and adversely impact biodiversity, particularly older forest associated species, has constrained the pace and scale of fuels management efforts. The California spotted owl (Strix occidentalis occidentalis), emblematic of this conundrum, will likely face local and widespread extirpation if wildfires continue to increase in size and severity. Here, we leveraged bioregional passive acoustic monitoring and a novel disturbance dataset in the Sierra Nevada, California to examine 1) the impact of disturbance legacies and fuels management on wildfire severity, 2) the effect of fuels management and wildfire severity on spotted owl occupancy across the bioregion, and 3) the net effects of fuels management on spotted owl occupancy via their direct (i.e., by altering habitat) and indirect effects (i.e., by changing fire behavior and mitigating severe fire effects). We found that the net effects of fuels management on spotted owl occupancy depended on their intensity. High-intensity fuels management (>= 35 % reduction in canopy cover) resulted in net increases in spotted owl occupancy when implemented across 1-25 % of a landscape. Low-intensity management (<35 % reduction in canopy cover) resulted in net increases to spotted owl occupancy when implemented across up to 100 % of a landscape. Combining low levels of high-intensity fuels management and high levels of lowintensity fuels management in occupied owl sites-in addition to conserving existing nesting and roosting habitat-may effectively modify fire behavior and directly create habitat structures that benefit spotted owls. Our work suggests that restoring resilient forests through fuels management and conserving a vulnerable forest specialist can be viewed as complementary objectives.

In fire-adapted forests around the world, nature-based solutions (NbS) are increasingly used as a tool to promote resilience to catastrophic fire through actions like fuels reduction and prescribed burning. This work also has many potential co-benefits, including climate change mitigation through stable carbon storage and biodiversity through habitat protection. One key mechanism for realizing both of these co-benefits is the protection of large and ancient trees, keystone components that sequester a disproportionate amount of carbon and serve as unique habitat for old forest associated species, many of which are declining or at risk of extinction. However, climate change poses a substantial risk to both tree recruitment and survival, either directly (temperature and drought tolerance) or indirectly (wildfire and insect occurrence). These impacts are not fully understood in the scientific literature nor, as a result, fully accounted for in the design of NbS management projects.Therefore, to help inform near-term NbS restoration priorities, we investigated how a changing climate will impact the retention of large trees on the landscape and the ecosystem functions they support. Focusing on the Sierra Nevada, California, USA, a biophysically diverse and at-risk mountain ecoregion, we evaluated the intersection of current and future climate with large tree occurrence and two critical functions: carbon storage and habitat for the California spotted owl (Strix occidentalis occidentalis; CSO), an old growth associated species whose core population is limited to the Sierra Nevada and that requires large trees for nesting habitat. We mapped large trees across the Sierra Nevada, evaluated the climatic drivers of large tree biogeography, and forecasted how conditions supportive of large tree populations might shift geographically in the future under two emission levels (RCP 4.5 and 8.5). Using a bivariate fuzzy logic approach, we mapped the joint probability of current CSO occupancy and carbon storage and then evaluated future climate vulnerabilities and associated management strategies. We found that carbon and CSO occupancy corresponded closely with the current distribution of large trees in the Sierra, primarily at mid-elevations in the central Sierra. Similarly, we found that these mid-elevation montane forests are likely to continue to support large trees and CSO habitat and carbon storage through mid-century (e.g., consistent with "monitor" and "protect" climate-informed management strategies). Conversely, climate conditions in the southern Sierra and the upper elevations of the central Sierra are likely to constrain the persistence and recruitment of large trees, affecting the potential to recruit CSO habitat and enhance the carbon storage of higher elevation forests. We hope these findings will encourage the design of and investment in climate-informed NbS projects, and we propose that this method could be used in other ecosystems to jointly assess the climate change mitigation and biodiversity impacts of NbS-based management.

The Anthropocene is defined by rapid environmental changes such as biological invasions and shifting disturbance regimes that threaten native species. Understanding the drivers of endangerment for species facing multiple simultaneous threats is challenging without experimental methods. Here, we examined the relative and combined effects of severe wildfires and an early-stage barred owl (Strix varia) invasion on an assemblage of three native forest owl species in the Sierra Nevada, California, USA, leveraging manipulative (lethal barred owl removals) and natural (severe wildfires) experiments and a regional passive acoustic monitoring program from 2018 to 2023. Wildfires reduced flammulated owl (Psiloscops flammeolus) occupancy by 71% in severely burned areas (sites experiencing near-complete high-severity fire) for at least 3 years postfire but did not affect great horned (Bubo virginianus) or northern pygmy owl (Glaucidium californicum) occupancy. Because flammulated owls have small home ranges and an insectivorous diet that depends on nearby mature forest foraging habitat and secondary-cavity nest sites, they showed a strong negative response to extensive high-severity burn areas that eliminate these resources. Flammulated owl occupancy increased approximately twofold from 0.09 (85% CI: 0.03, 0.20) to 0.18 (85% CI: 0.07, 0.36) following lethal barred owl removals (with only 4% posterior distribution overlap), but removals did not affect the other two native species. Despite evidence of habitat segregation between barred owls and the native species, where barred owls typically occupied intermediate-to-late seral forests in flatter, lower elevation areas, this niche partitioning was insufficient to prevent nonconsumptive or predatory effects on flammulated owls. In contrast, the resilience of great horned and pygmy owls may have stemmed from their larger body size and diurnal activity, respectively, suggesting that life history mediates forest owl vulnerability to invasive barred owls. The negative effects of barred owls on flammulated owls, even during the early invasion stage, coupled with well-documented effects on other small, nocturnal forest owl species in regions with high barred owl densities, reinforce the conservation value of proactive invasive species management. Our study demonstrates the power of regional-scale experimentation, facilitated by bioacoustic monitoring, for understanding biological community responses-mediated by species' life history-to rapid environmental changes.

Many regions of the world have seen an increase in highly destructive wildfires, driven by well-documented increases in burned area and growth of housing in the wildland–urban interface (WUI), which exposes more homes to fire. However, it is unclear whether wildfires are also becoming more destructive due to changes in wildfire behavior or in the development patterns of exposed communities. Here, we assessed trends in wildfire building exposure and destruction rates in the conterminous United States from 2002 to 2022. We mapped destroyed and surviving buildings within 100 m of all wildfires that destroyed 10 or more buildings (n = 362) and assessed trends relative to major ecoregions and vegetation types. We used logistic regression to assess relationships between destruction rates and landscape factors. We found that 10% of exposed buildings were destroyed in 2002–2012, but this percentage increased to 32% in 2013–2022. This increase was largely due to greater building exposure in evergreen forests in the northwestern United States, where exposed buildings were more than 3.4 times as likely to be destroyed as those in grass and shrublands. However, annual destruction rates also significantly increased in all other vegetation types and were correlated with development type, weather, and burn severity. These results indicate that increasing wildfire destruction in the United States has resulted not only from increased exposure but from rising rates of building destruction, potentially indicating more extreme wildfire behavior. This finding underscores the need to better understand how fuel management, community planning, and hardening buildings can reduce vulnerability.

Fire shapes biodiversity in many forested ecosystems, but historical management practices and anthropogenic climate change have led to larger, more severe fires that threaten many animal species where such disturbances do not occur naturally. As predators, owls can play important ecological roles in biological communities, but how changing fire regimes affect individual species and species assemblages is largely unknown. Here, we examined the impact of fire severity, history, and configuration over the past 35 years on an assemblage of six forest owl species in the Sierra Nevada, California, using ecosystem-scale passive acoustic monitoring. While the negative impacts of fire on this assemblage appeared to be ephemeral (1-4 years in duration), spotted owls avoided sites burned at high-severity for up to two decades after a fire. Low- to moderate-severity fire benefited small cavity-nesting species and great horned owls. Most forest owl species in this study appeared adapted to fire within the region's natural range of variation, characterized by higher proportions of low- to moderate-severity fire and relatively less high-severity fire. While some species in this assemblage may be more resilient to severe wildfire than others, novel "megafires" that are larger, more frequent, and contiguously severe may limit the distribution of this assemblage by reducing the prevalence of low- to moderate-severity fire and eliminating habitat for a closed-canopy species for multiple decades. Management strategies that restore historical low- to moderate-severity fire with small patches of high-severity fire and promote a mosaic of forest conditions will likely facilitate the conservation of this assemblage of forest predators.

Preserving biodiversity is a central goal of conservation, but, in practice, monitoring biodiversity often involves assessing population trends for one or a handful of species that are presumed proxies for biodiversity. Despite the popularity of surrogate species strategies, the links between biodiversity and surrogate species are rarely tested, especially across the broad spatial scales at which they are applied. We quantitatively evaluated a prominent surrogate species strategy across 25,000 km2 of California's Sierra Nevada, an ecosystem undergoing substantial forest loss due to changing fire regimes and climate. We used passive acoustic monitoring and multispecies occupancy models to quantify pairwise co-occurrence among 6 indicator species and much of the avian community (63 species). We found that 95% of the sampled avian community had a positive association with at least one indicator species and that latitude played an important role in shaping co-occurrence for many species. Our work provides an important test of a long-standing conservation tool, suggests that a well-chosen suite of surrogate species can represent the occurrence patterns of a large portion of the rest of the community, and demonstrates the importance of explicitly considering the spatial scale over which surrogate species are effective.

In many forests globally, resilience-focused restoration is necessary to prevent fire-driven regime shifts. However, restoration planning is challenged by limited resources for monitoring biodiversity responses to management intervention and to natural disturbances. Bioregional-scale passive acoustic monitoring, when combined with automated species identification tools and management-relevant habitat data, can be a tractable method to simultaneously monitor suites of complementary indicator species and rapidly generate species-specific information for resource managers. We demonstrate these methods by mapping the occurrence of ten avian indicator species while examining the impact of fire history on patterns of occurrence across 25,000 km(2 )of California's Sierra Nevada mountains. Monitoring complementary indicator species with rapidly developing bioacoustics technology and relating their occurrence to policy-ready habitat metrics have the potential to transform restoration planning by providing managers with high-resolution, ecosystem-scale information that facilitates adaptive management in an era of rapid environmental change.

Forested landscapes are naturally heterogeneous, with the distribution of resources influencing animal habitat selection at multiple spatial scales. However, anthropogenic activities and changing disturbance regimes have reorganized how forests are structured from fine- to landscape-scales, generally with unknown consequences for forest-associated wildlife. For instance, fire suppression and selective logging in the western US has led to more homogeneous forests with fewer small patches of early-successional vegetation. As forest management aims to improve forest resilience to extreme fire and drought by restoring historical disturbance regimes and modifying forest structure through fuel management, there is a need for studies that evaluate how animals respond to forest heterogeneity at multiple scales. Here, we estimated occupancy for the dusky-footed woodrat (Neotoma fuscipes), an important prey species for many forest predators including the California spotted owl (Strix occidentalis occidentalis), relative to forest structure and composition at site-, patch-, and landscape-scales within landscapes where forest heterogeneity was created by even-aged timber management. Woodrats were more likely to occupy sites with greater canopy cover, understory cover, and hardwoods - particularly tanoak (Notholithocarpus densiflorus) - and smaller patches of young forest. Woodrats were also more likely to occupy mature forests in close proximity to younger forests, suggesting that young forest patches with more favorable local conditions can produce populations that recruit into adjacent, lower-quality mature forests. Our results suggest that creating small (similar to 2 ha) patches of high-quality woodrat habitat (i.e., young forests with dense understory and hardwoods) could provide "fishing holes" for spotted owls and other predators by supporting higher woodrat densities in surrounding mature forests managed for fuels - thus helping to meet both spotted owl conservation and forest resilience objectives. More broadly, we highlight the benefits of multi-scale studies and demonstrate that restoring landscape heterogeneity, including the creation of small early-successional forests, may benefit species conservation without compromising efforts to improve resilience in forest ecosystems globally.

Characterizing natal dispersal can help manage the spread of invasive species expanding their ranges in response to land use and climate change. The Barred Owl (Strix varia) is a prominent example of an apex predator undergoing a rapid range expansion, having spread from eastern to western North America where it is now hyperabundant—threatening the Northern Spotted Owl (S. occidentalis caurina) with extinction and potentially endangering many other native species. We attached satellite tags to 31 Barred Owl juveniles at the southern leading edge of the Barred Owl’s expanding range in California to characterize natal dispersal patterns and inform management. Juveniles traveled up to 100 km from natal territories and experienced high mortality (annual survival = 0.204). At landscape scales, juveniles preferentially used forests, shrublands, and lower elevations during dispersal and avoided grasslands and burned areas. At finer scales, juveniles preferred shorter (younger) forests, lower elevations, and drainages, and avoided unforested areas. Our results suggest the Barred Owl range expansion is being driven primarily by high reproductive rates and densities despite low juvenile survival rates and dispersal through putatively suboptimal younger forests as a result of exclusion from high-quality habitat by territorial individuals. These findings also point to several strategies for conserving Spotted Owls and other native species in the Barred Owl’s expanded range, including: (1) creating and maintaining Barred Owl-free reserves bounded by open or high elevation areas; (2) creating reserves large enough to reduce immigration by long-distance dispersers; and (3) removing Barred Owls from large riparian corridors.

The California spotted owl (Strix occidentalis occidentalis) is an older-forest associated species that resides at the center of forest management planning in the Sierra Nevada and Southern California, USA, which are experiencing increasingly large and severe wildfires and drought-related tree mortality. We leveraged advances in passive acoustic survey technologies to develop an acoustically assisted survey design that could increase the efficiency and effectiveness of project-level surveys for spotted owls, allowing surveys to be completed in a single year instead of in multiple years. We deployed an array of autonomous recording units (ARUs) across a landscape and identified spotted owl vocalizations in the resulting audio using BirdNET. We then evaluated spatio-temporal patterns in spotted owl vocalizations near occupied territories and the ability of a crew na & iuml;ve to the location of occupied territories to locate spotted owls based on patterns of acoustic detections. After only 3 weeks of acoustic surveys, >_1 ARU within 750 m of all 17 occupied territories obtained spotted owl detections across >_2 nights. When active surveys using broadcast calling were conducted near ARUs with spotted owl detections by surveyors na & iuml;ve to territory occupancy status and locations, surveyors located owls in 93% to 100% of occupied territories with <= 3 surveys. To further improve the efficiency of spotted owl surveys, we developed a statistical model to identify and prioritize areas across the Sierra Nevada for different survey methods (active only, acoustically assisted, no surveys) based on the expected probability of occupancy predicted from remotely sensed measurements of tree height and historical occupancy. Depending on managers' tolerance for false negatives, this model could help identify large areas that might not benefit from surveys based on low expected occupancy probabilities and areas where acoustically assisted surveys might enhance survey effectiveness and efficiency. Collectively, these findings can help managers streamline the survey process and thus increase the pace of forest restoration while minimizing potential near-term adverse effects on California spotted owls.

Context The concept of landscape heterogeneity is central to species conservation; yet understanding the processes by which heterogeneity affects species can be challenging in practice. Complex and sometimes difficult-to-measure responses of species may reflect the outcome of life-history trade-offs shaped by different landscape properties. Objectives We tested the hypothesis that a mosaic of forest stand types affected hunting and breeding success for California spotted owls ( Strix occidentailis occidentalis ). Methods We integrated high-temporal-resolution GPS tags, video monitoring of nest sites, long-term assessments of reproductive status, and high-resolution remotely sensed vegetation data in a mixed-ownership landscape in the Sierra Nevada, California to test our hypothesis. Results Spotted owls made shorter nocturnal movements in homogenous territories with large areas of medium-aged forest apparently because this forest type allowed direct movement paths to foraging sites. However, spotted owls delivered prey at a higher rate to nest sites when they had more forest edge in their territory, which presumably provided greater access to large-bodied woodrat ( Neotoma spp.) prey. Further, spotted owl reproductive output was relatively high in heterogenous territories containing a mix of mature and open forest. Conclusions The benefits heterogenous forests provide to hunting success appeared to outweigh costs associated with additional commuting distance to foraging sites and provided potential fitness benefits to spotted owls. We suggest that the effects of landscape heterogeneity can vary not only among, but also within, species and can reflect the outcome of trade-offs among different life history activities. Understanding the effects of landscape properties on biological communities will benefit from additional empirical and mechanistic studies of individual species.

Lay Summary center dot Identifying where prey is captured can help understand high-quality hunting habitat for predators but is very difficult to do for small cryptic predators. center dot We combined high-resolution GPS and camera technology to examine how vegetation conditions influence prey capture, delivery rate, and reproductive success for a small nocturnal predator, the Spotted Owl (Strix occidentalis occidentalis). center dot Spotted Owl prey captures increased with heterogeneous vegetation, larger trees, complex multilayered canopies, and more forest-chaparral edge. Prey delivery increased with more cover type heterogeneity and forest-chaparral edge. center dot Spotted Owl reproductive success was higher in territories having taller canopies, greater canopy cover, and more shrubby vegetation. center dot Forest management activities that increase the number of large trees, promote multilayered canopies, and enhance vegetative heterogeneity are likely to benefit Spotted Owls. Predator-prey interactions can be profoundly influenced by vegetation conditions, particularly when predator and prey prefer different habitats. Although such interactions have proven challenging to study for small and cryptic predators, recent methodological advances substantially improve opportunities for understanding how vegetation influences prey acquisition and strengthen conservation planning for this group. The California Spotted Owl (Strix occidentalis occidentalis) is well known as an old-forest species of conservation concern, but whose primary prey in many regions-woodrats (Neotoma spp.)-occurs in a broad range of vegetation conditions. Here, we used high-resolution GPS tracking coupled with nest video monitoring to test the hypothesis that prey capture rates vary as a function of vegetation structure and heterogeneity, with emergent, reproductive consequences for Spotted Owls in Southern California. Foraging owls were more successful capturing prey, including woodrats, in taller multilayered forests, in areas with higher heterogeneity in vegetation types, and near forest-chapparal edges. Consistent with these findings, Spotted Owls delivered prey items more frequently to nests in territories with greater heterogeneity in vegetation types and delivered prey biomass at a higher rate in territories with more forest-chaparral edge. Spotted Owls had higher reproductive success in territories with higher mean canopy cover, taller trees, and more shrubby vegetation. Collectively, our results provide additional and compelling evidence that a mosaic of large tree forest with complex canopy and shrubby vegetation increases access to prey with potential reproductive benefits to Spotted Owls in landscapes where woodrats are a primary prey item. We suggest that forest management activities that enhance forest structure and vegetation heterogeneity could help curb declining Spotted Owl populations while promoting resilient ecosystems in some regions.

Wildfire risks to homes are increasing, especially in the wildland-urban interface (WUI), where wildland vegetation and houses are in close proximity. Notably, we found that more houses are exposed to and destroyed by grassland and shrubland fires than by forest fires in the United States. Destruction was more likely in forest fires, but they burned less WUI. The number of houses within wildfire perimeters has doubled since the 1990s because of both housing growth (47% of additionally exposed houses) and more burned area (53%). Most exposed houses were in the WUI, which grew substantially during the 2010s (2.6 million new WUI houses), albeit not as rapidly as before. Any WUI growth increases wildfire risk to houses though, and more fires increase the risk to existing WUI houses.