High climatic variability and livestock grazing are ubiquitous across greater sage-grouse (Centrocercus urophasianis) range and may influence the population dynamics of this imperiled rangeland species. We examined how annual variability in climate, vegetation productivity, grazing intensity, and conservation grazing program enrollment influenced a greater sage-grouse population in a 1500-km2 rangeland landscape in central Montana (2002-2022). Using a Gompertz density-dependent population model, we found that winter temperatures positively influenced annual population dynamics (standardized coefficient = 0.18; 95% CRI: 0.02-0.34). We found no clear evidence that annual dynamics were influenced by variation in the previous year's breeding season weather, drought indices, or remotely sensed rangeland productivity, unlike findings documented in other parts of sage-grouse range (e.g., Great Basin). We found no compelling evidence that landscape-scale variation in grazing intensity or percent area enrolled in 3-year conservation grazing program contracts affected populations. Our results suggest that, in a relatively intact rangeland of the northern Great Plains, drought sensitivity and prevailing grazing management did not limit populations. Strategies to protect or expand intact rangelands including those that encompass winter habitat should be evaluated further.

Understanding where on landscapes to make investments, such as designating protected areas, is a critical component of biodiversity management. Locations for management actions should achieve current management objectives while also having the best chance of continued success in the future. Climate change has the potential to undermine biodiversity management, as it may lead to substantial changes in environmental conditions that are outside local managers' control. Following changes in environmental conditions, areas on the landscape may become unsuitable for the species or habitats that the initial actions were intended to benefit. The potential for local actions to be undermined by global-scale threats makes it essential to account for and minimize exposure to temperature change. We present a series of analyses identifying priority areas for wildlife and habitat management. We conducted our analyses using a systematic landscape planning approach that identifies areas within species' ranges or current distributions of key habitats that are predicted to be less affected by future temperature change. We used the ranges of 142 animal and 149 plant species identified as species of greatest conservation need (SGCN) together with the distributions of 14 terrestrial and 19 aquatic key habitats in Utah, USA. We measured temperature change in 2 ways: as changes in mean annual temperature between 2020 and the year 2100 (temperature difference) and by quantifying how far a species range or habitat would have to shift to maintain its current temperature envelope (climate velocity). We identified the sub-watersheds with hydrologic unit code 12 (HUC 12) that collectively encompassed the ranges of our SGCNs and key habitats while minimizing overall exposure to temperature change. These high priority HUC 12s represented areas that were not only hotspots for SGCNs and key habitats but also acted as temperature refugia, where management actions are likely to be robust to temperature change. We hope that our identification of high-priority HUC 12s will help inform and guide future management actions to improve their long-term outcomes. This study identifies priority areas for wildlife and habitat management in Utah that are predicted to be less affected by future temperature changes. By using a systematic landscape planning approach, the research highlights high priority regions that act as temperature refugia, aiming to ensure effective and robust conservation efforts for 142 animal and 149 plant species, and 33 key habitats. image

Greater sage-grouse (Centrocercus urophasianus; sage-grouse) populations in the western United States have declined, necessitating conservation efforts. The United States Department of Agriculture Natural Resources Conservation Service and livestock producers implemented the Sage Grouse Initiative (SGI) to improve sage-grouse habitat using regional-specific management actions such as rotational grazing. We assessed the effect of SGI grazing management, the influence of brood female and chick morphometric traits, and multiple environmental and anthropogenic disturbance factors on chick mortality risk in a sage-grouse population in central Montana, USA, from 2011-2019. We used a Kaplan-Meier survival function to evaluate chick survival, Cox proportional hazards models to evaluate chick mortality risk as a function of brood female and chick morphometric traits, and the Andersen-Gill formulation of the Cox proportional hazards model to assess the effects of time-dependent habitat characteristics on chick mortality risk. Survival to 45 days post-hatch for 510 chicks varied annually from 0.26 +/- 0.07 (SE) to 0.69 +/- 0.07. The 45-day survival rate for all years combined was 0.51 +/- 0.03. Chick mortality risk was not affected by changes in livestock grazing management implemented through the SGI grazing program. Brood female age and body condition, sex of chicks, vegetation, and anthropogenic variables were also unassociated with chick mortality risk. There were small protective effects of chick mass adjusted for age and mean minimum monthly temperature; greater chick mass and lower monthly temperatures correlated with reduced mortality risk. Overall, our study suggests the SGI grazing program does not confer additional benefits to sage-grouse chicks beyond existing grazing practices. Incentivizing grazing practices that adhere to fundamental principles of rangeland ecology and maintain intact rangelands may be more effective than specific prescribed grazing systems for sage-grouse conservation in this region.

Sagebrush steppe is one of the most threatened ecosystems in North America. Adult density of songbirds within sagebrush steppe is a metric used to evaluate conservation actions. However, relying on only adult density to guide conservation may be misleading. Information on how conservation actions influence the nest density and nest survival of songbird species, in addition to adult density, are needed. We evaluated the relationships between nest density, nest survival, and adult density of Brewer's sparrow (Spizella breweri) and vesper sparrow (Pooecetes gramineus) over 3 breeding seasons in central Montana. Our findings suggest that adult pairs of both species were often present in higher numbers than nests, and this relationship was most prominent for Brewer's sparrows. However, our results do not support density dependence when considering nest survival. This discrepancy suggests that songbirds may not breed every year and that density dependence may be operating on nest densities within these populations differently than we examined. This study provides information on relationships between population demographics for 2 songbird species in grazed sagebrush steppe that will improve monitoring and management activities of conservation efforts.

The Thick-billed Longspur (Rhynchophanes mccownii) is a bird species of conservation concern that relies on shortgrass prairies and steppes of western North America. These habitats have been greatly altered from expansive and diverse ecosystems into small patches of homogeneous pastures interspersed with agricultural lands, yet little information exists on how land use affects Thick-billed Longspur demography. This study evaluates the benefits of an incentivized private land conservation-based program (CRP) on Thick-billed Longspur reproduction. We compared Thick-billed Longspur nest success and density on data collected on pastures enrolled in CBP with pastures not enrolled. CBP pastures experienced a rest-rotation specified grazing regime, while there were no requirements for the pastures outside the program. We use a time-to-event state-space superpopulation model that accounts for the availability of nests when estimating detection. We detected and monitored 74 Thick-billed Longspur nests over 2 breeding seasons, including 28 nests in CBP pastures. Our results suggest similar estimates of nest success and nest density between nests in CBP pastures and nests in pastures not participating in the conservation program. Our estimates of nest success and nest density advance our understanding of the influence of an incentivized conservation program on songbirds and give insight into 2 metrics of Thick-billed Longspur reproduction.

Variation in nutrient allocation can influence the timing of breeding and ultimately reproductive output. Time and space constraints might exist, however, if fewer food resources are available to meet the costs of reproduction early during the reproductive season. Here, for the first time, we test whether nutrient-allocation strategies for reproduction in a shrub-dependent avian species differ with timing of breeding in different ecoregions: a high-elevation landscape, containing spatially complex vegetation (Rocky Mountains) vs. a low-elevation, more homogenous landscape (Great Plains). We analyzed data collected from radio-telemetry and stable isotopes to assess the degree to which endogenous (body) reserves are used for reproduction and whether variation in allocation strategies was associated with time of year, ecoregion, habitat quality (including sagebrush type and plant greenness), or maternal characteristics. Using a Bayesian statistical framework, we found that females relied on a similar amount of endogenous reserves for reproduction in first nesting and renesting attempts. Additionally, endogenous contributions declined more rapidly throughout the nesting season in the Rocky Mountains than in the Great Plains. Individuals in high- and intermediate-elevation sagebrush types in the Rocky Mountains used similar amounts of endogenous reserves, whereas females nesting in low-elevation sagebrush used less. Females nesting at intermediate elevations, which experience the greatest flush of new green vegetation during the nesting season, switched their reliance from endogenous-to-exogenous sources for reproduction as green vegetation became available during spring. Our study highlights adaptations of a nutrient-allocation strategy across areas with varying levels of resources in time and space in a habitat specialist bird. Nutrient allocation by individuals residing in high-elevation areas favors a strategy that mainly uses nutrients gained from wintering habitats, whereas individuals residing in low-elevation areas mainly use exogenous sources for reproduction.

Habitat selection links individual behavior to population abundance and dynamics, so evaluation of habitat selection is necessary for conservation and management. Land management can potentially alter both the structure and composition of habitats, thus influencing habitat selection and population size. Livestock grazing is the dominant land use worldwide and, while overstocking has been linked to the decline of many wildlife species, properly managed grazing could improve habitat quality and maintain native rangeland habitats. We evaluated breeding season habitat selection of female sharp-tailed grouse, an indicator species for grassland ecosystems, in relation to grazing management and landscape features in eastern Montana and western North Dakota. At broad spatial scales, females selected for multiple landscape features, including grassland, but exhibited no selection for either landscape or management variables when selecting habitat at smaller spatial scales. Females selected for pastures managed with rest-rotation grazing when choosing a home range, but selection did not equate to improved fitness. Moreover, we observed strong individual variation in both home range size and third-order habitat selection. While the high variability among individuals makes specific management recommendations difficult, selection for grassland habitats at broad scales suggests that strategies that maintain intact native rangelands are important for the conservation of sharp-tailed grouse.

ABSTRACTLivestock grazing is a predominant land use worldwide and can influence wildlife populations by altering grassland composition, structure, and productivity. Conceptually, rest‐rotation livestock grazing could increase pasture‐level heterogeneity that would allow wildlife to balance the need for resources with the risk of predation. Prairie‐grouse (Tympanuchus spp.) are recognized as important indicator species for grassland ecosystems, so identifying management approaches suitable for prairie‐grouse could have implications for other species. We monitored radio‐collared female sharp‐tailed grouse (T. phasianellus) to evaluate the effects of 3 systems of livestock grazing management on the breeding season survival and habitat‐associated mortality risk of adult grouse in the northern mixed‐grass prairie in eastern Montana and western North Dakota, USA, during 2016–2018. Cumulative breeding season survival was 0.65 ± 0.04 (SE) and annual survival varied from 0.28 ± 0.04 to 0.50 ± 0.05. Grazing management did not have a meaningful influence on any aspect of the cumulative breeding season survival of adult female sharp‐tailed grouse, although the seasonal timing of peaks in mortality risk differed among systems. A 10% increase in cropland increased mortality risk of adult female sharp‐tailed grouse by a factor of 1.27. Overall, our results suggest that strategies that preserve economically viable ranching systems in unfragmented grasslands may have greater benefits for sharp‐tailed grouse survival than prescriptive livestock grazing systems. © 2020 The Wildlife Society.

Many grassland species coevolved with large herbivores and require habitats along the entire structural gradient created by grazing. Widespread declines of grassland birds, however, have prompted concerns about rangeland management. Conceptually, rest-rotation grazing functions as a conservation strategy to mimic historic disturbance regimes and create pasture-level heterogeneity in the absence of fire, but its utility for improving wildlife habitat has not been directly tested, particularly in the mesic mixed-grass prairie. We evaluated rest-rotation grazing as a conservation management technique compared with more traditional grazing systems, including summer rotation and season-long grazing, and assessed effects of different grazing systems and stocking rates on nest site selection and nest survival of sharp-tailed grouse (Tympanuchus phasianellus), an indicator species for grassland ecosystems. Both nest site selection and nest survival were directly related to vertical nesting cover, which was only weakly related to grazing management variables, including grazing system and stocking rate, at moderate stocking rates (≤ 2 animal unit month [AUM] ha−1). Cattle presence during the nesting period had a positive effect on daily nest survival, potentially through an effect by either the cows or rancher presence on predator behavior. Overall, our results suggest that rest-rotation grazing did not contribute to pasture-level vegetation heterogeneity and that both the selective foraging of cattle and inherent topographic and edaphic variability in our study area may be stronger drivers of heterogeneity at the small spatial scale required by female grouse.

Grassland birds have undergone substantial population declines throughout much of their historic ranges in North America. Most of the remaining grassland bird habitat is restricted to rangelands managed for livestock production, so grazing management has strong implications for grassland bird conservation efforts. We conducted 1 830 point-count surveys at 305 sites during 2016–2017 to evaluate the relative effects of three livestock grazing systems on the abundance and community composition of grassland birds in a northern mixed-grass prairie ecosystem of eastern Montana, United States. Our objectives were to 1) evaluate effects of grazing management on abundance and community composition of grassland obligate birds, focusing specifically on grazing systems, stocking rates, and interactions with rangeland productivity; 2) evaluate the importance of local vegetation characteristics for grassland birds within grazing systems; and 3) assess the effectiveness of rest-rotation grazing to create patch-heterogeneity in rangeland vegetation through the alteration of structural components and the response of grassland birds to these treatments. Overall, we found inconsistent responses in abundances of grassland birds relative to livestock grazing systems and no discernable differences among grazing systems relative to community composition. However, local abundances were often driven by interactions between grazing system and rangeland production potential, suggesting the effects of livestock grazing management were generally mediated by rangeland productivity. In addition, associations between avian abundance and grazing management parameters (e.g., stocking rate) were species specific. Ubiquitous guidelines for livestock grazing systems may be inappropriate for grassland bird conservation efforts in the northern mixed-grass prairie, and high stocking rates may negatively impact populations of dense-grass obligate grassland birds in this region.

ABSTRACTGrazing by domestic livestock is ubiquitous in the sagebrush (Artemisia spp.) biome of western North America. Widespread, long‐term population declines in greater sage‐grouse (Centrocercus urophasianus) have elicited concern about negative effects of livestock grazing on sage‐grouse populations. Hypothesized relationships, mostly untested, between livestock and sage‐grouse nesting ecology have played a prominent role in shaping public land livestock grazing policy and broader discussions about management of grazing in sagebrush ecosystems. We tested predictions arising from several commonly hypothesized mechanisms by which livestock may affect nesting habitat quality for sage‐grouse in a grazed landscape in central Montana, USA. We employed Bayesian variable selection methods to identify factors related to both nest site selection and nest success, focusing on indices of livestock use at local and pasture scales and including other factors known to influence nesting ecology such as anthropogenic features and weather. In spite of some evidence nest survival was positively associated with senesced vegetation height, evidence for effects of livestock presence and indices of local livestock use on nest site selection and survival was equivocal at best. In contrast, we found strong evidence that females selected nest sites based on relatively static features such as sagebrush cover and distance from gravel and paved roads, whereas nest failure was driven primarily by extended periods of heavy precipitation. Management of sage‐grouse nesting habitat in this region should focus on conserving areas of adequate shrub cover and preventing further fragmentation by roads. © 2018 The Wildlife Society.

ABSTRACTGrazing by domestic livestock is a ubiquitous land use in the sagebrush (Artemisia spp.) biome of western North America. Widespread, long‐term population declines in greater sage‐grouse (Centrocercus urophasianus) have elicited concern about potential negative effects of livestock management practices on sage‐grouse populations. We evaluated how recently implemented rotational grazing systems affected sage‐grouse nesting habitat quality as part of a large‐scale, replicated, natural experiment in central Montana, USA. We used Bayesian methods to assess support for effects of rotational grazing management and rest from grazing on daily survival rates of nearly 500 sage‐grouse nests monitored over 6 years, and mixed effects models to test for effects of rotational grazing and rest on vegetation structure. Though nests on rotationally grazed ranches displayed a trend toward greater daily survival rates, the evidence for an effect was weak. There was no evidence that rest from grazing (≥12 months) increased daily survival rates. Furthermore, rotational grazing systems and rest had negligible effects on herbaceous vegetation height and cover relative to other grazing strategies used in the study area. Results do not support the hypothesis that rotational grazing systems or rest from grazing increase nest success in the northern Great Plains. Estimated nest success, however, was comparable to range‐wide averages, suggesting concealing cover for nests is unlikely to be limiting growth of this population regardless of grazing strategy. In light of these results and recent research questioning reported relationships between grass height and nest survival, maximization of hiding cover may be overemphasized in grazing management guidelines and policies. Rather, our findings suggest a variety of locally appropriate grazing strategies focused on fundamental range health principles may provide adequate habitat quality for nesting sage‐grouse. © 2017 The Wildlife Society.

Sagebrush-steppe ecosystems in western US are characterized as a landscape mix of sagebrush shrubs and grass vegetation. A large portion of sagebrush-steppe across the west is used for grazing of domestic livestock, primarily cattle. We compared songbird communities over four breeding seasons in eastern Montana between two grazing systems: rest-rotation and traditional grazing. Rest-rotation involves grazing areas (or pastures) at different annual seasons across years allowing pastures to be rested between the same consecutive seasons. Traditional grazing is defined as grazing a pasture repeatedly at the same annual season each year. Recently, rest-rotation has been used as a conservation management tool by the Natural Resource Conservation Service’s (NRCS) Sage Grouse Initiative (SGI) program. The goal is to improve habitat for greater sage grouse (Centrocercus urophasianus) through livestock grazing. We explore the effects of rest-rotation compared to traditional grazing on songbird population breeding demographics: adult abundance, nest densities and nest success. Abundance is a metric often used to assess conservation actions given the ease in collecting data to estimate this parameter. However, information on how the conservation actions influences the life histories, such as nest density and nest success, that determine abundance are lacking. Our goal is to understand the relationship between patterns in abundance, nest density, and nest success and how rest-rotation grazing influences those patterns. This knowledge will provide information on how to best manage for multiple songbird species in sagebrush-steppe by determining how conservation management tool affects individual songbird populations.

AbstractMuch interest lies in the identification of manageable habitat variables that affect key vital rates for species of concern. For ground‐nesting birds, vegetation surrounding the nest may play an important role in mediating nest success by providing concealment from predators. Height of grasses surrounding the nest is thought to be a driver of nest survival in greater sage‐grouse (Centrocercus urophasianus; sage‐grouse), a species that has experienced widespread population declines throughout their range. However, a growing body of the literature has found that widely used field methods can produce misleading inference on the relationship between grass height and nest success. Specifically, it has been demonstrated that measuring concealment following nest fate (failure or hatch) introduces a temporal bias whereby successful nests are measured later in the season, on average, than failed nests. This sampling bias can produce inference suggesting a positive effect of grass height on nest survival, though the relationship arises due to the confounding effect of plant phenology, not an effect on predation risk. To test the generality of this finding for sage‐grouse, we reanalyzed existing datasets comprising >800 sage‐grouse nests from three independent studies across the range where there was a positive relationship found between grass height and nest survival, including two using methods now known to be biased. Correcting for phenology produced equivocal relationships between grass height and sage‐grouse nest survival. Viewed in total, evidence for a ubiquitous biological effect of grass height on sage‐grouse nest success across time and space is lacking. In light of these findings, a reevaluation of land management guidelines emphasizing specific grass height targets to promote nest success may be merited.

ABSTRACT Mechanisms underlying habitat use in most species are poorly understood. Therefore, we integrated behavioral and forest cover type data to test hypotheses underlying the choice of two key cover types used by male Ruffed Grouse (Bonasa umbellus) in northern Minnesota, USA. Forests of aspen (Populus spp.) are the presumptive highest quality cover type for Ruffed Grouse because this bird species achieves its highest breeding densities in this cover type. Yet, males select cover types of conifer even when nearby cover types of aspen remain vacant. We examined this conundrum – selection of inferior cover types when presumed better types are available – by randomly selecting 23 male Ruffed Grouse from among a contiguous population of territorial males and used automated video systems to monitor their breeding display behavior. We predicted that if conifer cover types were indeed inferior habitat for Ruffed Grouse, males that established territories in these cover types would either drum (auditory display) more frequently to attract mates or have fewer conspecific interactions, detected by observing visual display rates, than males which established territories in aspen cover types. We used drumming rates and visual display rates as two separate response variables, and used generalized linear models to evaluate each of these response variables as a function of several predictors in a priori models including cover type, male density on the study area, distance to the nearest neighbor, cover type of the nearest neighbor, and distance to the nearest neighbor in aspen cover. Information-theoretic model selection was used to rank these models with Akaike's Information Criterion adjusted for small sample sizes. The best predictor (top model) of drumming rates among our model set, was cover type, but our null model was competitive, which suggested uncertainty in our result. We were unable to explain visual display rates given our model set and predictor variables, because our intercept only [null] model was the top model, which suggested visual display behavior was not correlated with either cover type or the other factors we included in models. We conclude the reason grouse select display sites likely has more to do with suitable protective cover (i.e., predator avoidance) than with the general classification (aspen vs. conifer) of the cover type. Thus, the link between relative fitness and habitat selection of specific cover types is more likely to be revealed by studying the habitat requirements and survival probabilities of females visiting males which occupy these two prominent breeding-display covers.

Six years of point count data in eastern Nebraska and western Iowa, USA, were used to investigate how the community structure of grassland birds and the densities of four focal species (common yellowthroat, dickcissel, grasshopper sparrow and sedge wren) varied on conservation lands with differing management strategies (i.e., warm- versus cool-season grasses and low- to high-diversity plantings), and between conservation and unmanaged marginal grasslands (e.g., field borders and terraces). Model-selection results indicated that grasshopper sparrow and dickcissel densities were influenced by grassland type, with higher densities in parcels dominated by warm-season grasses. Species-specific changes in density in response to planting diversity reinforced the value of creating heterogeneous habitat for grassland birds. Densities for all four species were substantially lower in unmanaged marginal grasslands versus conservation parcels and the community structure between the two habitats differed significantly, with generalist species (e.g., American robins, common grackles and grassland species associated with shorter, sparse and patchy vegetation (e.g., horned lark and vesper sparrow)) largely replacing tallgrass specialists in unmanaged marginal grassland parcels. (C) 2014 Elsevier B.V. All rights reserved.

Partnerships across agencies and land ownerships established to maintain wildlife-compatible “working landscapes” are critical for conserving and managing wildlife in the West. Preliminary results from the first three years of a 10-yr study in central Montana demonstrate this management approach. We are evaluating prescribed grazing systems implemented by NRCS’s Sage Grouse Initiative (SGI) that are designed to improve hiding cover and food availability for Greater sage grouse (Centrocercus urophasianus) during critical life stages via voluntary, incentive-based modifications of livestock grazing management. Extensive vegetation sampling across 8 SGI-enrolled ranches and 20 non-enrolled ranches in 2013 revealed significant increases in residual grass height, live grass height, and herbaceous vegetation cover on SGI-enrolled lands. In 2011-2013, we monitored adult female sage-grouse and chicks with radiotelemetry to measure vital rates and habitat use. Annual hen survival ranged from 57-74 percent, nest success ranged from 12-61 percent, and chick survival ranged from 9-23 percent. Using an information theoretic approach in program MARK, the top-ranked nest success model showed that grass height was positively correlated with nest success. During late nesting to early brood rearing periods of 2012 and 2013 we used pitfall traps to collected ground-dwelling arthropods from cattle grazed and rest-rotation phase pastures enrolled in the SGI program. Collected arthropods were identified and appropriate specimens were classified as sage grouse chick food items. During both years of study, food item catches were greatest (P < 0.03) in rested versus grazed pastures indicating that strategic pasture rest may increase the availability of sage grouse chick food resources.

Abstract When land managers incorporate the habitat needs of grassland birds into their planning, they typically rely on management recommendations based on habitat use by adults during nesting. Habitat requirements for other critical life stages are seldom known and may differ from those of nesting adults. Using radio-telemetry, we examined survival and habitat use by juvenile Dickcissels (Spiza americana) during the postfledging period. In 2003 and 2004, we monitored 60 fledgling Dickcissels for ≤30 days after they left the nest. Mortality rates were highest during the first week after leaving the nest, and only 33% of the fledglings survived the first four weeks after leaving the nest. Estimated mean survival times were 16.9 ± 1.6 days after birds left the nest. In both years, fledgling survival was positively associated with dense vertical and horizontal structure of forbs at nests. Survival tended to be positively associated with vertical grass density on adult territories and negatively associated with patchily distributed forbs on adult territories. Fledgling habitat use was restricted to areas where Dickcissels nested and adjacent fields. Habitats used included corn and soybean fields, grasslands, and wetlands. Our results suggest that the fledgling period is a critical stage for Dickcissels and that fledglings require habitat similar to habitat used for nesting. Supervivencia Durante el Período Posterior al Emplumamiento en Spiza americana: Implicancias para el Manejo de Hábitat y Conservación