Greater Sage-Grouse Winter Habitat Selection and Energy Development

Abstract Recent energy development has resulted in rapid and large-scale changes to western shrub-steppe ecosystems without a complete understanding of its potential impacts on wildlife populations. We modeled winter habitat use by female greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB) of Wyoming and Montana, USA, to 1) identify landscape features that influenced sage-grouse habitat selection, 2) assess the scale at which selection occurred, 3) spatially depict winter habitat quality in a Geographic Information System, and 4) assess the effect of coal-bed natural gas (CBNG) development on winter habitat selection. We developed a model of winter habitat selection based on 435 aerial relocations of 200 radiomarked female sage-grouse obtained during the winters of 2005 and 2006. Percent sagebrush (Artemisia spp.) cover on the landscape was an important predictor of use by sage-grouse in winter. The strength of habitat selection between sage-grouse and sagebrush was strongest at a 4-km² scale. Sage-grouse avoided coniferous habitats at a 0.65-km² scale and riparian areas at a 4-km² scale. A roughness index showed that sage-grouse selected gentle topography in winter. After controlling for vegetation and topography, the addition of a variable that quantified the density of CBNG wells within 4 km² improved model fit by 6.66 Akaike's Information Criterion points (Akaike wt = 0.965). The odds ratio for each additional well in a 4-km² area (0.877; 95% CI = 0.834- 0.923) indicated that sage-grouse avoid CBNG development in otherwise suitable winter habitat. Sage-grouse were 1.3 times more likely to occupy sagebrush habitats that lacked CBNG wells within a 4-km² area, compared to those that had the maximum density of 12.3 wells per 4 km² allowed on federal lands. We validated the model with 74 locations from 74 radiomarked individuals obtained during the winters of 2004 and 2007. This winter habitat model based on vegetation, topography, and CBNG avoidance was highly predictive (validation R² = 0.984). Our spatially explicit model can be used to identify areas that provide the best remaining habitat for wintering sage-grouse in the PRB to mitigate impacts of energy development.     

Nest Site Selection by Greater Sage-Grouse in Mono County,California

ABSTRACT Loss of nesting habitat is believed to be a factor in the decline of greater sage-grouse (Centrocercus urophasianus) throughout its range. Few data are available for sage-grouse in Mono County, California, USA, in the most southwestern portion of the species’ range. We studied habitat selection of nesting sage-grouse in Mono County, California, from 2003 to 2005 by capturing and radiotracking females to identify nesting locations. We sampled vegetation at nest sites and randomly selected sites within 200 m of nests and within each of 5 subareas within Mono County. Nest sites were characterized by 42.4 ± 1.3% (x̄ ± SE) shrub canopy cover, 10.5 ± 1.0 cm residual grass height, and 2.7 ± 1.0% residual grass cover. Shrub cover was the only variable found to differentiate nest sites from randomly selected sites. Unlike some other studies, we did not find understory vegetation to be important for selecting nest sites. Mean shrub cover was 38.7 ± 1.5% at random sites within 200 m of nests and 33.6 ± 1.6% at random sites at the approximate scale of home ranges, indicating that nesting females selected nesting areas that contained denser shrubs than their home range, and nest sites that contained greater shrub cover than the vicinity immediately surrounding nests. Our results suggest that managers should consider managing for greater shrub cover in Mono County than what is currently called for in other parts of sage-grouse range and that management for sage-grouse habitat may need to be tied more closely to local conditions.     

Landscape-Level Assessment of Brood Rearing Habitat for Greater Sage-Grouse in Nevada

Abstract: Loss of quality brood rearing habitat, resulting in reduced chick growth and poor recruitment, is one mechanism associated with decline of greater sage-grouse (Centrocercus urophasianus) populations. Low chick survival rates are typically attributed to poor-quality brood rearing habitat. Models that delineate suitability of sage-grouse nesting or brood rearing habitat at the landscape scale can provide key insights into the relationship between sage-grouse and the environment, allowing managers to identify and prioritize habitats for protection or restoration. We used Southwest Regional Gap landcover types to identify early and late greater sage-grouse brood rearing in east-central Nevada. We conducted an Ecological Niche Factor Analysis to 1) examine the effect these landcover types and other ecogeographical variables have on sage-grouse selection of brood rearing habitat, and 2) generate landscape-scale suitability maps. We also evaluated if incorporating a fitness component (brood survival) in landscape spatial analyses of habitat quality influenced our assessment of habitat suitability. Because 36% of our 6,500-km² study area was identified as early brood rearing habitat, we believe this habitat may not be limiting greater sage-grouse populations in east-central Nevada, USA, at least in wet years. We found strong selection for particular landcover types (e.g., higher elevation, moist sites with riparian shrubs or montane sagebrush) during late brood rearing. Late brood rearing habitat on which broods were successfully reared represented only 2.8% of the study area and had a restricted distribution, suggesting the potential that such habitat could limit sage-grouse populations in east-central Nevada.     

Sage-Grouse Habitat Selection During Winter in Alberta

ABSTRACT Greater sage-grouse (Centrocercus urophasianus) are dependent on sagebrush (Artemisia spp.) for food and shelter during winter, yet few studies have assessed winter habitat selection, particularly at scales applicable to conservation planning. Small changes to availability of winter habitats have caused drastic reductions in some sage-grouse populations. We modeled winter habitat selection by sage-grouse in Alberta, Canada, by using a resource selection function. Our purpose was to 1) generate a robust winter habitat-selection model for Alberta sage-grouse; 2) spatially depict habitat suitability in a Geographic Information System to identify areas with a high probability of selection and thus, conservation importance; and 3) assess the relative influence of human development, including oil and gas wells, in landscape models of winter habitat selection. Terrain and vegetation characteristics, sagebrush cover, anthropogenic landscape features, and energy development were important in top Akaike's Information Criterion-selected models. During winter, sage-grouse selected dense sagebrush cover and homogenous less rugged areas, and avoided energy development and 2-track truck trails. Sage-grouse avoidance of energy development highlights the need for comprehensive management strategies that maintain suitable habitats across all seasons.     

Greater Sage-Grouse Population Response to Energy Development and Habitat Loss

ABSTRACT Modification of landscapes due to energy development may alter both habitat use and vital rates of sensitive wildlife species. Greater sage-grouse (Centrocercus urophasianus) in the Powder River Basin (PRB) of Wyoming and Montana, USA, have experienced rapid, widespread changes to their habitat due to recent coal-bed natural gas (CBNG) development. We analyzed lek-count, habitat, and infrastructure data to assess how CBNG development and other landscape features influenced trends in the numbers of male sage-grouse observed and persistence of leks in the PRB. From 2001 to 2005, the number of males observed on leks in CBNG fields declined more rapidly than leks outside of CBNG. Of leks active in 1997 or later, only 38% of 26 leks in CBNG fields remained active by 2004–2005, compared to 84% of 250 leks outside CBNG fields. By 2005, leks in CBNG fields had 46% fewer males per active lek than leks outside of CBNG. Persistence of 110 leks was positively influenced by the proportion of sagebrush habitat within 6.4 km of the lek. After controlling for habitat, we found support for negative effects of CBNG development within 0.8 km and 3.2 km of the lek and for a time lag between CBNG development and lek disappearance. Current lease stipulations that prohibit development within 0.4 km of sage-grouse leks on federal lands are inadequate to ensure lek persistence and may result in impacts to breeding populations over larger areas. Seasonal restrictions on drilling and construction do not address impacts caused by loss of sagebrush and incursion of infrastructure that can affect populations over long periods of time. Regulatory agencies may need to increase spatial restrictions on development, industry may need to rapidly implement more effective mitigation measures, or both, to reduce impacts of CBNG development on sage-grouse populations in the PRB.     

Ecological Factors Influencing Nest Survival of Greater Sage-Grouse in Mono County,California

ABSTRACT We studied nest survival of greater sage-grouse (Centrocercus urophasianus) in 5 subareas of Mono County, California, USA, from 2003 to 2005 to 1) evaluate the importance of key vegetation variables for nest success, and 2) to compare nest success in this population with other greater sage-grouse populations. We captured and radiotracked females (n = 72) to identify nest sites and monitor nest survival. We measured vegetation at nest sites and within a 10-m radius around each nest to evaluate possible vegetation factors influencing nest survival. We estimated daily nest survival and the effect of explanatory variables on daily nest survival using nest-survival models in Program MARK. We assessed effects on daily nest survival of total, sagebrush (Artemisia spp.), and nonsagebrush live shrub-cover, Robel visual obstruction, the mean of grass residual height and grass residual cover measurements within 10 m of the nest shrub, and area of the shrub, shrub height, and shrub type at the nest site itself. Assuming a 38-day exposure period, we estimated nest survival at 43.4%, with percent cover of shrubs other than sagebrush as the variable most related to nest survival. Nest survival increased with increasing cover of shrubs other than sagebrush. Also, daily nest survival decreased with nest age, and there was considerable variation in nest survival among the 5 subareas. Our results indicate that greater shrub cover and a diversity of shrub species within sagebrush habitats may be more important to sage-grouse nest success in Mono County than has been reported elsewhere.     

Greater sage-grouse winter habitat use on the eastern edge of their range

Greater sage-grouse (Centrocercus urophasianus) at the western edge of the Dakotas occur in the transition zone between sagebrush and grassland communities. These mixed sagebrush (Artemisia sp.) and grasslands differ from those habitats that comprise the central portions of the sage-grouse range; yet, no information is available on winter habitat selection within this region of their distribution. We evaluated factors influencing greater sage-grouse winter habitat use in North Dakota during 2005–2006 and 2006–2007 and in South Dakota during 2006–2007 and 2007–2008. We captured and radio-marked 97 breeding-age females and 54 breeding-age males from 2005 to 2007 and quantified habitat selection for 98 of these birds that were alive during winter. We collected habitat measurements at 340 (177 ND, 163 SD) sage-grouse use sites and 680 random (340 each at 250 m and 500 m from locations) dependent sites. Use sites differed from random sites with greater percent sagebrush cover (14.75% use vs. 7.29% random; P < 0.001), percent total vegetation cover (36.76% use vs. 32.96% random; P ≤ 0.001), and sagebrush density (2.12 plants/m² use vs. 0.94 plants/m² random; P ≤ 0.001), but lesser percent grass cover (11.76% use vs. 16.01% random; P ≤ 0.001) and litter cover (4.34% use vs. 5.55% random; P = 0.001) and lower sagebrush height (20.02 cm use vs. 21.35 cm random; P = 0.13) and grass height (21.47 cm use vs. 23.21 cm random; P = 0.15). We used conditional logistic regression to estimate winter habitat selection by sage-grouse on continuous scales. The model sagebrush cover + sagebrush height + sagebrush cover × sagebrush height ( = 0.60) was the most supported of the 13 models we considered, indicating that percent sagebrush cover strongly influenced selection. Logistic odds ratios indicated that the probability of selection by sage-grouse increased by 1.867 for every 1% increase in sagebrush cover (95% CI = 1.627–2.141) and by 1.041 for every 1 cm increase in sagebrush height (95% CI = 1.002–1.082). The interaction between percent sagebrush canopy cover and sagebrush height (β = −0.01, SE ≤ 0.01; odds ratio = 0.987 [95% CI = 0.983–0.992]) also was significant. Management could focus on avoiding additional loss of sagebrush habitat, identifying areas of critical winter habitat, and implementing management actions based on causal mechanisms (e.g., soil moisture, precipitation) that affect sagebrush community structure in this region. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Using Human-Imprinted Chicks to Evaluate the Importance of Forbs to Sage-Grouse

Abstract Although several studies have indicated the importance of forbs in brood habitats, no studies have quantified direct effects of the amount of forb cover on sage-grouse (Centrocercus urophasianus) chicks. In 2002 and 2003, we conducted field experiments in Middle Park and Moffat County, Colorado, USA, respectively. Our objective was to quantify effects of 3 levels of forb cover in brood habitat on mass gain and feather growth of human-imprinted sage-grouse chicks. The results indicate that increasing forb cover in brood areas with <20% forb cover may lead to increased chick survival and grouse productivity.     

Factors Affecting Nest Survival of Greater Sage-Grouse in Northcentral Montana

Abstract: We studied greater sage-grouse (Centrocercus urophasianus) in northcentral Montana, USA, to examine the relationship between nest success and habitat conditions, environmental variables, and female sage-grouse characteristics. During 2001-2003, we radiomarked 243 female greater sage-grouse, monitored 287 nests, and measured 426 vegetation plots at 4 sites in a 3,200-km² landscape. Nest survival varied with year, grass canopy cover, daily precipitation with a 1-day lag effect, and nesting attempt. In all years, daily survival rate increased on the day of a rain event and decreased the next day. There was temporal variation in nest success both within and among years: success of early (first 28 d of nesting season) nests ranged from 0.238 (SE = 0.080) in 2001 to 0.316 (SE = 0.055) in 2003, whereas survival of late (last 28 d of nesting season) nests ranged from 0.276 (SE = 0.090) in 2001 to 0.418 (SE = 0.055) in 2003. Renests experienced higher survival than first nests. Grass cover was the only important model term that could be managed, but direction and magnitude of the grass effect varied. Site, shrub and forb canopy cover, and Robel pole reading were less useful predictors of nest success; however, temporal and spatial variation in these habitat covariates was low during our study. We note a marked difference between both values and interpretations of apparent nest success, which have been used almost exclusively in the past, and maximum-likelihood estimates used in our study. Annual apparent nest success (0.46) was, on average, 53% higher than maximum-likelihood estimates that incorporate individual, environmental, and habitat covariates. The difference between estimates was variable (range = +8% to +91%). Management of habitats for nesting sage-grouse should focus on increasing grass cover to increase survival of first nests and contribute to favorable conditions for renesting, which should be less likely if survival of first nests increases.     

Reptiles Under the Conservation Umbrella of the Greater Sage-Grouse

In conservation paradigms, management actions for umbrella species also benefit co-occurring species because of overlapping ranges and similar habitat associations. The greater sage-grouse (Centrocercus urophasianus) is an umbrella species because it occurs across vast sagebrush ecosystems of western North America and is the recipient of extensive habitat conservation and restoration efforts that might benefit sympatric species. Biologists' understanding of how non-target species might benefit from sage-grouse conservation is, however, limited. Reptiles, in particular, are of interest in this regard because of their relatively high diversity in shrublands and grasslands where sage-grouse are found. Using spatial overlap of species distributions, land cover similarity statistics, and a literature review, we quantified which reptile species may benefit from the protection of intact sage-grouse habitat and which may be affected by recent (since about 1990) habitat restoration actions targeting sage-grouse. Of 190 reptile species in the United States and Canadian provinces where greater sage-grouse occur, 70 (37%) occur within the range of the bird. Of these 70 species, about a third (11 snake and 11 lizard species) have >10% of their distribution area within the sage-grouse range. Land cover similarity indices revealed that 14 of the 22 species (8 snake and 6 lizard species) had relatively similar land cover associations to those of sage-grouse, suggesting greater potential to be protected under the sage-grouse conservation umbrella and greater potential to be affected, either positively or negatively, by habitat management actions intended for sage-grouse. Conversely, the remaining 8 species are less likely to be protected because of less overlap with sage-grouse habitat and thus uncertain effects of sage-grouse habitat management actions. Our analyses of treatment databases indicated that from 1990 to 2014 there were at least 6,400 treatments implemented on public land that covered approximately 4 million ha within the range of the sage-grouse and, of that, >1.5 million ha were intended to at least partially benefit sage-grouse. Whereas our results suggest that conservation of intact sagebrush vegetation communities could benefit ≥14 reptiles, a greater number than previously estimated, additional research on each species' response to habitat restoration actions is needed to assess broader claims of multi-taxa benefits when it comes to manipulative sage-grouse habitat management. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.     

Recovery of Greater Sage-Grouse Habitat Features in Wyoming Big Sagebrush following Prescribed Fire

The ability of prescribed fire to enhance habitat features for Greater Sage-Grouse ( Centrocercus urophasianus ) in Wyoming big sagebrush ( Artemisia tridentata wyomingensis ) in western North America is poorly understood. We evaluated recovery of habitat features important to wintering, nesting, and early brood-rearing Sage-Grouse in Wyoming big sagebrush following prescribed fire. Our case study included 1 year of preburn (1989) and 10 years of postburn data collected over 14 years (1990–2003) from control and burned study areas in the Big Desert of southeastern Idaho, U.S.A. We compared recovery and rate of change for 12 features in four categories between burned and control transects and recovery in burned transects including change in variation. Our results indicate that prescribed fire induced quantifiable changes in wintering, nesting, and early brood-rearing Sage-Grouse habitat features 14 years after fire in Wyoming big sagebrush in our study area. Specifically, grass and litter required by Sage-Grouse for nest and brood concealment recovered relatively rapidly following fire; major forb cover was similar between burned and control sites, but the rate of increase for major forb cover and richness was greater in control transects, and structurally mediated habitat features required by Sage-Grouse for food and cover in winter and for nest and brood concealment in spring recovered slowly following fire. Because shrub structural features in our study did not recover in magnitude or variability to preburn levels 14 years after fire, we recommend that managers avoid burning Wyoming big sagebrush to enhance Sage-Grouse habitat, but rather implement carefully planned treatments that maintain Sagebrush.     

Greater sage‐grouse respond positively to intensive post‐fire restoration treatments

Habitat loss is the most prevalent threat to biodiversity in North America. One of the most threatened landscapes in the United States is the sagebrush (Artemisia spp.) ecosystem, much of which has been fragmented or converted to non‐native grasslands via the cheatgrass‐fire cycle. Like many sagebrush obligates, greater sage‐grouse (Centrocercus urophasianus) depend upon sagebrush for food and cover and are affected by changes to this ecosystem. We investigated habitat selection by 28 male greater sage‐grouse during each of 3 years after a 113,000‐ha wildfire in a sagebrush steppe ecosystem in Idaho and Oregon. During the study period, seeding and herbicide treatments were applied for habitat restoration. We evaluated sage‐grouse responses to vegetation and post‐fire restoration treatments. Throughout the 3 years post‐fire, sage‐grouse avoided areas with high exotic annual grass cover but selected strongly for recovering sagebrush and moderately strongly for perennial grasses. By the third year post‐fire, they preferred high‐density sagebrush, especially in winter when sagebrush is the primary component of the sage‐grouse diet. Sage‐grouse preferred forb habitat immediately post‐fire, especially in summer, but this selection preference was less strong in later years. They also selected areas that were intensively treated with herbicide and seeded with sagebrush, grasses, and forbs, although these responses varied with time since treatment. Wildfire can have severe consequences for sagebrush‐obligate species due to loss of large sagebrush plants used for food and for protection from predators and thermal extremes. Our results show that management efforts, including herbicide application and seeding of plants, directed at controlling exotic annual grasses after a wildfire can positively affect habitat selection by sage‐grouse.     

Thresholds and Time Lags in Effects of Energy Development on Greater Sage-Grouse Populations

ABSTRACT Rapid expansion of energy development in some portions of the Intermountain West, USA, has prompted concern regarding impacts to declining greater sage-grouse (Centrocercus urophasianus) populations. We used retrospective analyses of public data to explicitly investigate potential thresholds in the relationship between lek attendance by male greater sage-grouse, the presence of oil or gas wells near leks (surface occupancy), and landscape-level density of well pads. We used generalized linear models and generalized estimating equations to analyze data on peak male attendance at 704 leks over 12 years in Wyoming, USA. Within this framework we also tested for time-lag effects between development activity and changes in lek attendance. Surface occupancy of oil or gas wells adjacent to leks was negatively associated with male lek attendance in 5 of 7 study areas. For example, leks that had ≥ 1 oil or gas well within a 0.4-km (0.25-mile) radius encircling the lek had 35–91% fewer attending males than leks with no well within this radius. In 2 of these 5 study areas, negative effects of well surface occupancy were present out to 4.8 km, the largest radius we investigated. Declining lek attendance was also associated with a higher landscape-level density of well pads; lek attendance at well-pad densities of 1.54 well pads/km² (4 well pads/mile²) ranged from 13% to 74% lower than attendance at unimpacted leks (leks with zero well pads within 8.5 km). Lek attendance at a well-pad density of 3.09 well pads/km² (8 well pads/mile²) ranged from 77% to 79% lower than attendance at leks with no well pad within 8.5 km. Further, our analysis of time-lag effects suggested that there is a delay of 2–10 years between activity associated with energy development and its measurable effects on lek attendance. These results offer new information for consideration by land managers on spatial and temporal associations between human activity and lek attendance in sage-grouse, and suggest that regional variation is an important consideration in refining existing management strategies.     

Use of Implanted Radiotransmitters to Estimate Survival of Greater Sage-Grouse Chicks

ABSTRACT Reduced chick survival has been implicated in declines of greater sage-grouse (Centrocercus urophasianus) populations. Because monitoring survival of unmarked sage-grouse chicks is difficult, radiotelemetry may be an effective technique to estimate survival rates, identify causes of mortality, and collect ecological data. Previous studies have used subcutaneous implants to attach radiotransmitters to hatchlings of several species of birds with precocial young. Previous researchers who used subcutaneous implants in free-ranging populations removed chicks from the capture location and implanted transmitters at an alternate site. Because logistics precluded removing newly hatched greater sage-grouse chicks from the field, we evaluated a method for implanting transmitters at capture locations. We captured 288 chicks from 52 broods and monitored 286 radiomarked chicks daily for 28 days following capture during May and June 2001–2002. Two (>1%) chicks died during surgery and we did not radiomark them. At the end of the monitoring period, 26 chicks were alive and 212 were dead. Most (98%, 207/212) radiomarked chick mortality occurred < 21 days posthatch and predation (82%, 174/212) was the primary cause of death. Necropsies of 22 radiomarked chicks did not indicate inflammation or infection from implants, and they were not implicated in the death of any chicks. Fate of 48 chicks was unknown because of transmitter loss (n = 16), radio failure (n = 29), and brood mixing (n = 3). Overall, the 28-day chick survival rate was 0.220 (SE = 0.028). We found that mortalities related to the implant procedure and transmitter loss were similar to rates reported by previous researchers who removed chicks from capture sites and implanted transmitters at an alternate location. Subcutaneous implants may be a useful method for attaching transmitters to newly hatched sage-grouse chicks to estimate survival rates, identify causes of mortality, and collect ecological data.     

Survival of Greater Sage-Grouse Chicks and Broods in the Northern Great Basin

ABSTRACT Reduced annual recruitment because of poor habitat quality has been implicated as one of the causative factors in the range-wide decline of sage-grouse (Centrocercus urophasianus) populations since the 1950s. Because chick and brood survival are directly linked to annual recruitment and may be the primary factors that limit sage-grouse population growth, we estimated 28-day survival rates of radiomarked chicks and broods from 2000 to 2003. We examined relationships between survival and several habitat variables measured at brood sites, including food availability (insects and forbs); horizontal cover of sagebrush, grasses, and forbs; and vertical cover of sagebrush and grass. We monitored 506 radiomarked chicks from 94 broods; chick survival was 0.392 (SE = 0.024). We found evidence that both food and cover variables were positively associated with chick survival, including Lepidoptera availability, slender phlox (Phlox gracilis) frequency, total forb cover, and grass cover. The effect of total grass cover on chick survival was dependent on the proportion of short grass. The hazard of an individual chick's death decreased 8.6% (95% CI = −1.0 to 18.3) for each percentage point increase in total grass cover when the proportion of short grass was >70%. Survival of 83 radiomarked broods was 0.673 (SE = 0.055). Lepidoptera availability and slender phlox frequency were the only habitat variables related to brood survival. Risk of total brood loss decreased by 11.8% (95% CI = 1.2–22.5) for each additional Lepidoptera individual and 2.7% (95% CI = −0.4 to 5.8) for each percentage point increase in the frequency of slender phlox found at brood sites. Model selection results revealed that temporal differences in brood survival were associated with variation in the availability of Lepidoptera and slender phlox. Years with high brood survival corresponded with years of high Lepidoptera availability and high slender phlox frequency. These foods likely provided high-quality nutrition for chicks during early growth and development and enhanced survival. Habitat management that promotes Lepidoptera and slender phlox abundance during May and June (i.e., early brood rearing) should have a positive effect on chick and brood survival in the short term and potentially increase annual recruitment.     

Nest Predation of Greater Sage-Grouse in Relation to Microhabitat Factors and Predators

ABSTRACT Nest predation is a natural component of greater sage-grouse (Centrocercus urophasianus) reproduction, but changes in nesting habitat and predator communities may adversely affect grouse populations. We used a 2-part approach to investigate sage-grouse nest predation. First, we used information criteria to compare nest survival models that included indices of common raven (Corvus corax) abundance with other survival models that consisted of day of incubation, grouse age, and nest microhabitat covariates using measurements from 77 of 87 sage-grouse nests. Second, we used video monitoring at a subsample of 55 of 87 nests to identify predators of depredated nests (n = 16) and evaluated the influence of microhabitat factors on the probability of predation by each predator species. The most parsimonious model for nest survival consisted of an interaction between day of incubation and abundance of common ravens (w_{ravenXincubation day} = 0.67). An estimated increase in one raven per 10-km transect survey was associated with a 7.4% increase in the odds of nest failure. Nest survival was relatively lower in early stages of incubation, and this effect was strengthened with increased raven numbers. Using video monitoring, we found the probability of raven predation increased with reduced shrub canopy cover. Also, we found differences in shrub canopy cover and understory visual obstruction between nests depredated by ravens and nests depredated by American badgers (Taxidea taxus). Increased raven numbers have negative effects on sage-grouse nest survival, especially in areas with relatively low shrub canopy cover. We encourage wildlife managers to reduce interactions between ravens and nesting sage-grouse by managing raven populations and restoring and maintaining shrub canopy cover in sage-grouse nesting areas.     

Achieving Better Estimates of Greater Sage-Grouse Chick Survival in Utah

Abstract: Declining sage-grouse (Centrocercus urophasianus) populations may be characterized by poor recruitment largely attributed to low chick survival. However, few published studies have explicitly examined factors that influence chick survival. We used a suture method to radiomark 1-2-day-old sage-grouse chicks (n = 150) in 2005-2006 on Parker Mountain in south-central Utah, USA, and monitored their survival to 42 days. We modeled effects of year, hatch date, chick age, brood-female age, brood-mixing, and arthropod abundance on chick survival. Our best model revealed an average survival estimate of 0.50 days to 42 days, which is the highest level ever documented for this long-lived species. Brood-mixing occurred in 21% (31/146) of chicks and 43% (18/42) of broods we studied. Moreover, yearling females had more chicks leave their broods than did adults. We found that survival may be higher among chicks that switch broods compared to those that stayed with their natal mother until fledging. Thus, brood-mixing may be an adaptive strategy leading to increased sage-grouse chick survival and higher productivity, especially among chicks born to yearling females. Our findings also indicate that arthropod abundance may be an important driver of chick survival, particularly during the early brood-rearing period and, therefore, sage-grouse populations may benefit from a management strategy that attempts to increase arthropod abundance via brood habitat management.     

Greater Sage-Grouse Response to the Physical Footprint of Energy Development

Energy infrastructure and associated habitat loss can lead to reduced reproductive rates for a variety of species including the greater sage-grouse (Centrocercus urophasianus). Our goal was to refine our understanding of how the physical footprint of energy development relates to sage-grouse nest and brood survival. Our survival analyses were conditional upon the amount of surface disturbance female sage-grouse were exposed to during reproductive stages. We quantified levels of exposure and compared them to the surface disturbance levels of the surrounding area. From 2008–2014, we collected data in 6 study areas in Wyoming, USA, containing 4 primary types of renewable and nonrenewable energy development. Our research focused on press disturbance (i.e., disturbance sustained after initial disturbance and associated with existing energy infrastructure and human activity). Our results suggest exposure to press disturbance during nesting and brood-rearing was related to lower nest and brood survival, which manifested at different spatial scales. Our analysis of nest survival suggested that the likelihood of a successful nest was negatively associated with the amount of press disturbance within an 8-km² area. Broods exposed to any press disturbance within a 1-km² area were less likely to survive compared to broods not exposed to press disturbance. Female sage-grouse consistently used habitat with lower disturbance levels during reproductive periods. Greater than 90% of nest and brood-rearing locations were in habitat with <3% press disturbance within a 2.7-km² area. Our research links surface disturbance associated with press disturbance to reproductive costs incurred by sage-grouse exposed to diverse energy development. Our results demonstrate a pattern of female avoidance of areas where press disturbance was high during nesting and brood-rearing and survival of nests and broods were highest in areas that had the least amount of disturbance. Our findings underscore the importance of minimizing disturbance to maintain viable sage-grouse populations. © 2020 The Wildlife Society.     

Crucial nesting habitat for gunnison sage-grouse: A spatially explicit hierarchical approach

Gunnison sage-grouse (Centrocercus minimus) is a species of special concern and is currently considered a candidate species under Endangered Species Act. Careful management is therefore required to ensure that suitable habitat is maintained, particularly because much of the species' current distribution is faced with exurban development pressures. We assessed hierarchical nest site selection patterns of Gunnison sage-grouse inhabiting the western portion of the Gunnison Basin, Colorado, USA, at multiple spatial scales, using logistic regression-based resource selection functions. Models were selected using Akaike Information Criterion corrected for small sample sizes (AIC_c) and predictive surfaces were generated using model averaged relative probabilities. Landscape-scale factors that had the most influence on nest site selection included the proportion of sagebrush cover >5%, mean productivity, and density of 2 wheel-drive roads. The landscape-scale predictive surface captured 97% of known Gunnison sage-grouse nests within the top 5 of 10 prediction bins, implicating 57% of the basin as crucial nesting habitat. Crucial habitat identified by the landscape model was used to define the extent for patch-scale modeling efforts. Patch-scale variables that had the greatest influence on nest site selection were the proportion of big sagebrush cover >10%, distance to residential development, distance to high volume paved roads, and mean productivity. This model accurately predicted independent nest locations. The unique hierarchical structure of our models more accurately captures the nested nature of habitat selection, and allowed for increased discrimination within larger landscapes of suitable habitat. We extrapolated the landscape-scale model to the entire Gunnison Basin because of conservation concerns for this species. We believe this predictive surface is a valuable tool which can be incorporated into land use and conservation planning as well the assessment of future land-use scenarios. © 2011 The Wildlife Society.