Wildfire is an increasingly important driver of changes within sagebrush (Artemisia spp. L.) ecosystems of the western USA, often resulting in increased spread of exotic annual grasses, such as cheatgrass (Bromus tectorum L.), and subsequent losses of native vegetation and wildlife habitat. Fuel breaks— areas of land treated to reduce or redistribute fuel loads — are widely implemented to help prevent the spread of wildfires and provide areas to facilitate firefighting efforts. However, localized installation and maintenance of fuel breaks directly reduce or remove vegetation and may propagate the spread of exotic annual grasses into fuel break boundaries and surrounding areas, inadvertently weakening ecological resilience to disturbance. To investigate if exotic annual grass cover was associated with mowed or green strip fuel breaks across the sagebrush biome, we combined multiple data sources and methodologies. We used targeted field surveys and land-management agency monitoring data within a space-for-time substitution framework coupled with a progressive-change before-after control-impact (PC BACI) study design using historical remotely sensed vegetation cover data which allowed us to account for potential confounding effects of roads on annual grass cover. Models using both field collected and remotely sensed vegetation indices estimated increases in exotic annual grass cover over time following mowed fuel break installation, and higher exotic annual grass cover closer to mowed fuel breaks. These increases in exotic annual grass occurred within, at 500 m and at 1000 m from mowed fuel breaks. However, we found variable patterns of exotic annual grass after green strip fuel break installation depending on the data source. No increase in exotic annual grass were indicated by either analysis at distances greater than 500 m from green strip fuel breaks. However, our and field data analyses disagreed on the direction of the association of exotic annual grass cover and green strip fuel breaks. Although fuel breaks are an important tool in managing wildland fire, our analysis underscores the importance of planting fire-resistant vegetation, rather than mowing alone, to reduce invasion by annual grasses within and around fuel breaks in sagebrush ecosystems. In addition, site characteristics that hinder the proliferation of exotic annual grasses could be evaluated when installing fuel breaks to minimize unintended effects of exotic annual grass on surrounding sagebrush habitat.

Abstract Common ravens ( Corvus corax ; ravens) are generalist avian predators whose populations have rapidly increased across North America, concomitant with anthropogenic development. Raven populations are bolstered by anthropogenic food and nesting resources in areas outside of their historical range and are impactful predators for many prey species of conservation concern, including greater sage‐grouse ( Centrocercus urophasianus ; sage‐grouse), primarily through reductions in sage‐grouse nest survival. Previous research suggests that coating developing raven eggs in non‐toxic oil, a form of egg‐addling, positively affects sensitive prey species because the nesting ravens no longer need to provision for young, and thereby forage less. We sought to understand the effects of oiling raven eggs on raven population density and reproductive success, as well as nest survival and population growth rate of co‐occurring populations of sage‐grouse. By evaluating oil‐treated, control, and sham‐treated (applied water rather than oil) raven nests in a before‐after‐control‐impact (BACI) research study design, we found that application of oil to raven eggs reduced raven egg hatchability by 94.5% and reduced raven densities at treatment sites relative to control sites. Sage‐grouse nest survival probabilities more than doubled at egg‐oiled treatment sites, resulting in a relative increase of 93.0% at treatment sites relative to control sites over the same period of inference. Finally, estimated abundances of sage‐grouse increased at oil‐treated sites by 44% relative to controls following oil treatments of raven eggs, also measured in a BACI framework. Oiling of raven eggs had strong and immediate impacts on co‐occurring populations of sage‐grouse and ravens.

The ongoing expansion of human enterprise into remote environments has contributed to degradation and fragmentation of ecosystems globally, reducing plant and animal species' habitats and viability. Western North America's sagebrush ecosystems have been reduced to half the area of their historical range, largely driven by anthropogenic activities. A relatively recent advancement has been the rapid construction of wireless communication infrastructure. While modern communication technology is essential for economic progress and critical to rural communities, its associated infrastructure may have undesired influences on sagebrush ecosystems and associated wildlife. These influences, along with their potential remediation to benefit species conservation, are poorly understood. We investigated the effects of communication tower infrastructure over 25 years (1996-2020) on the greater sage-grouse (Centrocercus urophasianus; hereafter, sage-grouse), a species of conservation concern often considered to be an indicator for the health of sagebrush ecosystems. We used hierarchical population state-space models coupled with male lek counts to investigate spatiotemporal effects of towers on sage-grouse annual rate of change ((lambda))over cap in apparent abundance while considering influences of other anthropogenic infrastructure and environmental characteristics at multiple spatial scales. Both tower density and proximity were negatively related to (lambda)over cap at distances up to 12.5 km away from tower sites. Higher elevation and sagebrush cover positively influenced (lambda)over cap while tree cover and annual grass cover exhibited negative associations. We used model results to inform a decision support framework that could guide location siting of future communication infrastructure based on minimization of effects to sage-grouse populations. Increases in communication tower infrastructure was one of the factors contributing to a similar to 1.6 % overall decrease in expected (lambda)over cap during the study, but simulations demonstrated how placing infrastructure away from sage-grouse breeding areas could minimize negative effects. Our findings, coupled with decision support analyses, can help inform local, regional, and national conservation strategies that seek to minimize or mitigate undesired effects of communication infrastructure.

Natural resource managers strive to improve restoration efficiency across the vast network of public lands of the United States, seeking the best return on investment through innovation, geographic prioritization, and adaptive management. This challenge is exemplified by ecosystems dominated by sagebrush (Artemisia spp.), which occur across the western United States and have been degraded by increasing wildfire frequency driven by invasive plant spread, among other factors. However, both costs and effectiveness of sagebrush restoration can vary spatially due to management practices in addition to biotic and abiotic factors, and characterizing this variation could inform broad-scale planning. We leveraged published models of sagebrush recovery and treatment costs to predict and evaluate cost-effectiveness of aerial and drill seeding Artemisia spp. across 429 718 km2 that overlapped 12 US states. Compared to natural recovery, effectiveness for both methods was generally low, yet effectiveness was often greater, and costs were always greater, for drill than aerial seeding, resulting in slightly higher cost-effectiveness on average for drill seeding. Cost-effectiveness for both treatments increased near major roads and in areas with more repeated burns. Cost-effectiveness also increased with predisturbance cover of sagebrush but decreased with herbaceous cover. However, we also identified areas where aerial seeding was more cost-effective than drill seeding, particularly with greater slope. Our results provide spatially explicit estimates and potential mechanisms of cost-effectiveness for two common seeding methods for sagebrush, which can help prioritize limited resources, guide land use, and improve restoration efficiency and effectiveness across public rangelands of the western United States.

We compiled and verified a comprehensive inventory dataset of communication tower infrastructure across the range of the greater sage-grouse (Centrocercus urophasianus) and Gunnison sage-grouse (Centrocercus minimus), two species of conservation concern that are viewed as ecosystem health indicators for the entire sagebrush biome within the United States. Our dataset includes all known towers with emphasis on validating construction year and month for towers built between 1990-2023. The annual spatial time series format of the data allows users to visualize, assess, and download tower locations and duration (including dates of construction and dismantlement) across the sagebrush biome of the western U.S. Tower data were acquired from publicly available infrastructure databases and records were filtered to include communication tower structures within the area of interest. Data records were validated and checked for accuracy with high resolution aerial and satellite imagery, and a subset were verified during field visits. The final filtered dataset comprises 4,322 tower sites, of which 3,528 tower site locations were verified via satellite imagery or field visits, and 794 were unverified tower sites (tower presence could not be confirmed via satellite imagery). Each tower record includes geographic coordinates, structure height, estimated date of construction, number of towers at each site, and, if applicable, date of dismantlement. The data product closes spatiotemporal gaps and resolves discrepancies present in other public versions of similar data and can be used in ecological research, infrastructure planning/siting/permitting, decision support tools for biological or landscape management, environmental assessments, or general use pertaining to the historic and current locations of communication infrastructure across sagebrush ecosystems.

Aim: Population ecologists often focus on changes in the distribution and abundance of wildlife species, which are useful for trend analyses and status assessments. However, rarely are these responses evaluated simultaneously for a single species, despite their unique contributions to fully assess a species' viability. For example, focusing solely on total abundance can mask important losses in overall distribution within a metapopulation structure that may contribute to long-term population instability that results from the extirpation of small peripheral populations. Location: Bi-State region of Nevada and California, USA. Methods: We simultaneously evaluated changes in population abundance and distribution for greater sage-grouse (hereafter sage-grouse; Centrocercus urophasianus) within the Bi-State Distinct Population Segment (DPS), a genetically distinct and isolated population straddling the border of Nevada and California. We combined population counts, demographic data, and information on space use from marked individuals to evaluate changes in population distribution and abundance over three time periods that corresponded to the three most recent population nadirs (1995-2019, 2002-2019 and 2008-2019). Results: The Bi-State DPS exhibited evidence of similar to 1.2%-2.5% declines annually, over the short/medium-term (1995-2019; (lambda) over cap = 0.987, 95% CRI: 0.970-0.999), short-term (2002-2019; (lambda) over cap = 0.975, 95% CRI: 0.963-0.985) and recent-term (2008-2019; (lambda) over cap = 0.988, 95% CRI: 0.973-1.001). Since 1995, the spatial distribution of sage-grouse abundance in the Bi-State DPS shifted amongst subpopulations, with peripheral subpopulations suffering the largest declines. Main Conclusions: Gains in abundance and distribution amongst expanding subpopulations did not offset losses in the remaining subpopulations, with a net loss in occupied distribution of 156 km(2) since 1995. Reductions in spatial distribution could have implications for metapopulation persistence as peripheral populations become more vulnerable to stochastic events, which would not have been apparent from the evaluation of overall metapopulation abundance on its own.

Greater sage-grouse (Centrocercus urophasianus; hereafter, sage-grouse) populations have declined across their range, resulting in high conservation concerns among state and federal wildlife managers. While interspecific nest parasitism by chukar (Alectoris chukar) on sage-grouse nests has been observed previously, the parasitic effects benefiting or harming the reproduction of either species are unknown. Additionally, while chukar eggs have been documented in sage-grouse nests previously, we know of no documented occurrences of chukar chicks parasitizing sage-grouse broods. Here, we report a novel observation of interspecific brood parasitism on a 9-day-old sage-grouse brood by a chukar chick in the Virginia Mountains of northwestern Nevada. Because chukar are an introduced exotic species whose western North American distribution largely overlaps sage-grouse distribution, understanding the dynamics and implications of brood parasitism may inform wildlife management strategies and conservation efforts for sage-grouse throughout their range.

Accurate maps of habitat availability for greater sage-grouse (Centrocercus urophasianus) across broad extents are of paramount importance to conservation efforts in sagebrush ecosystems across the Great Basin, particularly for habitat assessments and mitigation efforts. However, the ability to manage sage-grouse microhabitat is constrained by the spatial and spectral resolution of most remotely sensed vegetation products. Fractional approaches that yield estimates of percent cover at relatively coarse resolution (e.g., 30 ×30 m pixels) are well suited for regional and local estimates at relatively broad spatial scales (e.g., third-order macrohabitat selection and availability). However, precision at individual pixels that could represent finer selection patterns by sage-grouse (e.g., fourth-order microhabitat selection) is often poor. Here, results are presented from a study in central Nevada where previous fractional mapping approaches are advanced by applying regression tree (Cubist) modeling techniques at finer spatial resolutions, with estimates of shrub cover in training plots derived from ultra-high-resolution (< 3 cm) imagery collected with uncrewed aircraft systems (UAS) being applied to multi-spectral WorldView-2 scenes. The approach yields fractional estimates of shrub cover at a 2 m resolution. Compared to other fractional products, this product more closely correlates with actual field measurements that reflect finer selection patterns of sage-grouse. An advantage of the UAS-regression tree approach is that large volumes of training data can be collected rapidly from UAS compared to traditional ground-based vegetation surveys, which could ultimately yield previously lacking estimates of microhabitat availability across macrohabitat or landscape level extents. Our results provide high-resolution maps of shrub cover with multiple conservation applications, including the development of continuous microhabitat maps to inform sage-grouse habitat restoration efforts and incorporation into planning tools that simulate outcomes of multiple sagebrush management decisions.

Global climate change is contributing to declines in biodiversity, although changes vary across geographic regions and species. The iconic greater sage-grouse (Centrocercus urophasianus; sage-grouse) is central to conservation within the North American sagebrush ecosystem, yet its vulnerability to climate effects remains poorly understood. We used hierarchical models to explore weather and climatic influences on sage-grouse across nearly four decades, focusing first on pattern (population change), then process (demographic life stage). We quantified eight indicators of temperature and/or moisture conditions across time lags of 0-1.5 years leading up to current year breeding activities. Sage-grouse population growth tended to increase following above-average growing season precipitation. Precipitation or drought timing influenced whether process effects were positive or negative. More summer and/or fall moisture corresponded with increases in subsequent year brood and adult survival, while concurrent seasonal drought led to reductions in nest survival. Positive concurrent spring drought associations with adult and brood survival were largely outweighed by positive prior year moisture effects. Density-dependence and indirect effects of precipitation through vegetation and forage resource pathways likely contributed to nuanced responses across life stages. Our research improves mechanistic understanding of this indicator species' sensitivity to climatic factors, while reinforcing the importance of large-scale conservation initiatives for sagebrush ecosystems.

Pinyon and juniper ecosystems in the interior western United States are undergoing changes due to wildfire, drought, climate change, and associated disturbance agents (e.g., insect outbreak), while also infilling within some existing woodlands and expanding into other ecosystems (e.g., sagebrush). These multiple, often interacting disturbances are likely affecting wildlife, including species of conservation concern. However, study findings have been highly varied, conflicting, or constrained by data availability. We performed a systematic literature review to provide an overview of wildlife responses to disturbance in pinyon-juniper (PJ) ecosystems, identifying and cataloguing published literature based on geography, study type, primary research focus, ecological characteristics, and response type. We then applied a narrative approach to synthesize the current knowledge from the included studies to identify important knowledge gaps and to identify future research priorities. Our findings highlight the complexity and variability in wildlife responses to disturbance. Drought, insect outbreak, and wildfire impact PJ-associated wildlife in multifaceted ways, with species responses differing based on habitat type and species-specific traits. We also identify notable gaps in the research literature, due in part to taxonomic biases (limiting exploration of the diversity of PJ ecosystems and associated taxa), a lack of data on long-term and interacting disturbance effects (particularly under experimental conditions), and a limited understanding of direct mechanisms driving wildlife responses. Filling these research gaps and monitoring wildlife in PJ ecosystems can inform long-term management and improve the resiliency of wildlife communities in these important ecological systems.

Conservation translocation (hereafter translocation), the intentional movement of organisms from one location to another as a management tool, can be an extremely useful conservation action to increase the abundance of isolated populations following successful habitat restoration. However, managers seek to weigh the benefits against costs to the source population from which individuals are removed. Using two small and imperiled greater sage-grouse (Centrocercus urophasianus; hereafter sage-grouse) populations, we demonstrated the usefulness of translocation as a conservation management tool and the value of evaluating the potential consequences of translocation action. Using integrated population models and a before-after-control-impact (BACI) design, we quantified the extent to which translocation influenced the finite rate of change (lambda) of apparent abundance (N) in both reinforced and source populations. We also assessed changes in underlying demographic rates in one population, allowing for identification of the specific mechanisms causing differences in population trends following translocation. In both reinforced populations, 2 substantially increased following translocation. In the population for which we had sufficient demographic data, the increase in 2 resulted from a 179 % increase in egg hatchability following reinforcement. In one translocation, we did not observe adverse effects on the source populations. The source population for the second translocation exhibited reduced population growth rates after translocation, although BACI ratios indicated causes for population declines independent of trans- location effects, highlighting the need to investigate processes together with observed patterns. Overall, we demonstrated the ability to rescue isolated sage-grouse populations via translocation, preserving population viability and metapopulation persistence.

We fit an N -mixture model to lek (breeding area) count data to estimate annual population sizes of greater sage-grouse ( Centrocercus urophasianus ; sage-grouse) within the state of Oregon, USA between 2017–2024. Population estimates were delineated among 24 Priority Areas for Conservation (PACs) and considered additional sources of information including male-to-female sex ratios, lek attendance rates, numbers of unmodeled leks, and the existence of unsampled/unknown leks. In 2024, the state of Oregon was estimated to contain approximately 41,875 sage-grouse (95% credible interval [CRI] = 38,980–54,634), which was down from a high of 50,869 (95% CRI = 41,794–66,238) in 2017. A nadir (low point) was identified during 2019, when the median statewide population estimate was 30,644 birds. A complete population oscillation was not evident during the inferential period based on local maxima that were observed during the start (2017) and stop (2024) years of analysis. In addition to estimating population sizes, we evaluated N -mixture model estimates for precision and accuracy after randomly removing single and repeat counts in 10% increments (relative to total sample size). We estimated an increase in absolute bias of approximately 1.6% for every 10% reduction in effort. ### Competing Interest Statement The authors have declared no competing interest. Oregon Department of Fish and Wildlife, https://ror.org/00w64gh11 United States Geological Survey, https://ror.org/035a68863

Robust science is needed to inform natural resource management and policy decisions. Predictive species habitat maps are frequently employed in conservation decision-making but are often based on a single metric representing habitat quality. We outlined a framework that combines multiple spatially explicit indices of potential habitat quality that could be used to identify and prioritize habitat management areas, using the greater sage-grouse (Centrocercus urophasianus; hereafter sage-grouse) as an example species. Due to large-scale changes in sagebrush ecosystems, sage-grouse have suffered significant population declines in recent decades and have become key to land management plans throughout the western United States, where comprehensive habitat maps are crucial to effective conservation efforts. We evaluated habitat selection and survival patterns of sage-grouse across six distinct annual life stages and seasons to generate predictive habitat map surfaces, mapped the distribution of current occupancy, and combined maps of potential selection and survival patterns with space use and occupancy indices to delineate example habitat management categories. Our approach facilitates identification of priority areas to target for habitat preservation and areas where anthropogenic impacts could occur with likely minimal impact to the species. Overall, by combining indices representing selection, survival, and current occupancy, we provide a framework to allow for a flexible and targeted management approach that could be adapted to a wide variety of species.

Anthropogenic infrastructure has contributed to increasing common raven ( Corvus corax ) abundance across the Great Basin region of the United States, particularly in sagebrush ecosystems, where high raven densities are correlated with reduced sage‐grouse ( Centrocercus urophasianus ) nest survival. Our understanding of how raven reproductive behavior affects sage‐grouse nest predation is limited, especially considering their overlapping breeding seasons. Understanding differences in space use and resource selection between breeding and non‐breeding ravens could help identify high‐use areas and corresponding predation risk for sage‐grouse nests. We analyzed space use and resource selection of breeding ( n = 13) and non‐breeding ( n = 32) global positioning system (GPS)‐marked ravens in Nevada, USA (2017–2022) during the breeding season (1 March–31 June). We compared home‐range size, core area size, step lengths, and resource selection within a Bayesian framework with inference made by comparing Bayesian credible intervals (CRI). We generated home range and core area estimates using autocorrelated kernel density methods. We did not find a difference in home range size between breeding (469.33 km 2 , 95% CRI = 228.79–709.45 km 2 ) and non‐breeding (525.26 km 2 , 95% CRI = 410.71–654.10 km 2 ) ravens. However, breeding ravens had smaller core areas (10.77 km 2 , 95% CRI = 3.16–35.78 km 2 ) and shorter step lengths (1,160.33 m/hr, 95% CRI = 1,087.78–1,277.17 m/hr) than non‐breeding ravens (core area = 279.50 km 2 , 95% CRI = 206.77–363.72 km 2 ; step length = 1,953.74 m/hr, 95% CRI = 1,898.42–2,009.56 m/hr). Ravens in both breeding classes selected high normalized difference vegetation index (NDVI) and low annual grass and shrub cover, but non‐breeding ravens showed stronger selection for low annual grass and shrub cover areas. We found strong differences in selection between breeding classes for 6 of our 9 covariates: distance to road, solar radiation, distance to natural water, distance to forest edge, percent annual grass cover, and percent shrub cover. Non‐breeding ravens concentrated activity near forest edges, natural water sources, and anthropogenic features, whereas breeding ravens focused activity close to their nests. Our findings suggest that raven management could be more effective if it targeted areas with high NDVI and low annual grass and shrub cover, especially in anthropogenically modified landscapes and near forest edges, and prevented raven nest establishment near prey populations of concern.

Habitat features needed by wildlife can change in composition throughout the year, particularly in temperate ecosystems, leading to distinct seasonal spatial‐use patterns. Studies of species‐habitat associations therefore often focus on understanding relationships within discrete seasonal periods with common goals of prediction (e.g., habitat mapping) and inference (e.g., interpreting model coefficients). Across the range of the greater sage‐grouse ( Centrocercus urophasianus ) of western North America, the increasing use of high‐frequency tracking devices has led to a surge in habitat association studies covering multiple temporal periods and spatial extents. We reviewed the literature for seasonal habitat association studies corresponding to the second and third orders of selection (Johnson 1980). Our objectives were to summarize the methodological approaches used to estimate habitat associations to aid understanding in cross‐study comparisons and identify common habitat features reported as selected or avoided within different seasonal periods. We reviewed 71 second‐ and third‐order studies published from 2007–2023 that evaluated covariates collected in a geographic information system (GIS) and modeled probability of selection or intensity of use. The most common study design evaluated a single level of selection (third‐order) and was multi‐scale (i.e., covariates were measured at varying spatial grains). The most common model approach estimated habitat associations using resource selection functions (RSFs) fit with logistic regression. Studies mostly focused on the breeding periods and winter, but all seasons throughout the annual cycle were covered. There was clear support for selection of sagebrush and avoidance of trees and rugged terrain across seasons, and strong selection of mesic conditions in summer. However, habitat associations for most covariates were mixed, with proportionally equivalent selection and avoidance reported, even within the same seasons. Different factors hampered cross‐study comparisons, including variation in study design, but additional contributors likely included important context‐dependent habitat associations, such as functional responses to changing habitat availability. We suggest collaborative studies leveraging multiple datasets can help improve seasonal habitat inference by removing the effects of variable study designs.

The frequency and extent of wildfire are increasing globally, and understanding the ecosystem impacts of fire can help guide management of burned areas. Cyanobacteria are widespread in surface soils of semi-arid and arid rangelands and confer soil stabilization and resistance to exotic-plant invasions. We examined the probability of encountering cyanobacteria of the order Oscillatoriales in 2022, via microscopic counts of rewetted soils in the lab, following nine recent wildfires that burned as recently as 2012-2017 and up to four times repeatedly until then, in the northern Great Basin of the western U.S. Much of the variability in Oscillatoriales was attributed to the identity of the wildfire, i.e. unexplained variation. Tree cover estimated from gridded satellite-based models was scarce before and especially after fire yet was the second-most predictive covariate. Estimated cover of Oscillatoriales (lab derived) was 0.48 where trees were absent compared to 0.42 where tree cover was detected in the 30-m pixel surrounding soil samples. Presence of sand conferred nearly the opposite effect, which was counter to expectations but could be related to reduced vegetative cover on coarser soils. Other site factors including climatic precipitation and soil fertility were also predictive of Oscillatoriales. Cyanobacteria are considered to be cosmopolitan, i.e. ubiquitous in soils, but these spatial patterns of Oscillatoriales indicate relationships to landscape factors that have not been considered before. Understanding these relationships could aid land managers in identifying post-fire conditions most favorable to soil stabilizing cyanobacteria, which, in turn, could help achieve management goals of moderating soil erosion and additional invasion of fire-promoting exotic plants.

Since the passage of the Wild Free-Roaming Horses and Burros Act of 1971, federal agencies have been responsible for managing free-roaming equids in the United States. Over the last 20 years, management has been hampered by direct opposition from advocacy groups, budget limitations, and a decline in the public's willingness to adopt free-roaming horses (Equus caballus). As a result, free-roaming equid numbers have increased to >3 times the targeted goal of 26,785 (horses and burros [E. asinus] combined), the cumulative sum of the appropriate management levels (AML) for all 177 designated herd management areas (HMA) managed by the Bureau of Land Management. This increase is one of the causes of greater sage-grouse (Centrocercus urophasianus) population declines, owing to habitat alteration from free-roaming equids exacerbated by ongoing drought. To evaluate potential demographic mechanisms influencing these declines, we compiled survival data from 4 studies in central Wyoming, USA, including 995 adult female (first-year breeders or older) sage-grouse during the breeding season, 1,075 nests, 372 broods, and 136 juveniles (i.e., overwinter survival for fledged young), from 2008-2022. During this period, we also obtained population information for free-roaming horses from 9 HMAs used by individual grouse in our sample. Population estimates of free-roaming horses for these HMAs ranged from 59% to 7 times of the maximum appropriate management level (AML(max)). Sage-grouse monitored outside of HMAs represented control populations and, because we assumed they were not exposed to populations of free-roaming horses, we set values of AML(max) to zero for all grouse located outside of HMAs. To evaluate whether free-roaming horses were negatively affecting sage-grouse, we modeled daily survival of breeding age females, nest, broods, and juveniles. There was strong or moderate evidence that overabundant free-roaming horses negatively affected nest, brood, and juvenile survival. When horse abundance increased from AML(max) to 3 times AML(max), survival was reduced 8.1%, 18.3%, 18.2%, and 18.2% for nests, early broods (<= 20 days after hatch), late broods (>20 days to 35 days after hatch), and juveniles, respectively. These results indicate increasing free-roaming horse numbers affected vital rates for important life stages of sage-grouse, and that maintaining free-roaming horse numbers below AMLmax would reduce negative effects to sage-grouse populations.

First posted February 23, 2024 For additional information, contact: Western Ecological Research CenterU.S. Geological Survey3020 State University Drive EastSacramento, California 95819 Greater sage-grouse (Centrocercus urophasianus) are at the center of state and national land-use policies largely because of their unique life-history traits as an ecological indicator for health of sagebrush ecosystems. This updated population trend analysis provides state and federal land and wildlife managers with best-available science to help guide management and conservation plans aimed at benefitting sage-grouse populations. This analysis relied on previously published population trend modeling methodology from Coates and others (2021, 2022a) and incorporates population lek count data for 1960–2023. Included in this update are changes in terminology. Specifically, we now use the terms Period 1 (previously Long), Period 2 (previously Medium/Long), Period 3 (previously Medium), Period 4 (previously Short/Medium), Period 5 (previously Short), and Period 6 (previously Recent) to identify specific trends. State-space models estimated 2.8-percent average annual decline in sage-grouse populations between 1966 and 2021 (Period 1, six population oscillations) across their geographical range. Average annual decline among climate clusters for the same number of oscillations ranged between 2.1 and 3.1 percent. Cumulative declines were 41.1, 64.5, and 78.4 percent range-wide during Period 5 (19 years), Period 3 (35 years), and Period 1 (55 years), respectively. Population growth during 2022 and 2023 continue to point to 2021 as the most recent range-wide nadir.