Detecting the disappearance of active leks is the most efficient way to determine large declines in greater sage‐grouse (Centrocercus urophasianus) populations; thus, understanding factors that influence lek abandonment is critical. We evaluated factors that may have influenced the probability of sage‐grouse lek abandonment in the Bighorn Basin (BHB) of north‐central Wyoming from 1980 to 2009. Our objective was to examine lek abandonment based on landscape characteristics that explain differences between occupied and unoccupied leks. We evaluated lek abandonment from 144 occupied and 39 unoccupied leks from the Wyoming Game and Fish Department lek database with sufficient data for our 30‐year analysis. We conducted our analysis with binary logistic regression using landscape predictor variables obtained from geographic coverages at 5 scales (1.0‐, 3.2‐, 4.0‐, 5.0‐, and 6.4‐km radii around leks) to evaluate how these disturbances have influenced lek abandonment. Coverages included anthropogenic characteristics such as agricultural development, oil and gas development, prescribed burned treatments, and roads; and environmental characteristics such as vegetation attributes and wildfire. Our combined model included the number of oil and gas wells in a 1.0‐km radius, percent area of wildfire in a 1.0‐km radius, and variability in shrub height in a 1.0‐km radius around sage‐grouse leks. Abandoned (unoccupied) leks had 1.1‐times the variability of shrub height in a 1.0‐km radius, 3.1‐times the percentage of wildfire in a 1.0‐km radius, and 10.3‐times the number of oil and gas wells in a 1.0‐km radius compared to occupied leks. The model‐averaged odds of lek persistence with every 1 unit increase in oil and gas wells within a 1.0‐km radius was 0.66 (90% CI: 0.37–0.94), odds with every 1% increase in wildfire in a 1.0‐km radius was 0.99 (90% CI: 0.85–1.12), and odds with every 1 unit increase in the standard deviation of shrub height within a 1.0‐km radius around a lek was 0.77 (90% CI: 0.45–1.08). Because the 90% confidence intervals around the odds ratios of wells did not overlap 1.0, we suggest this predictor variable was most influential in our model‐averaged estimates. The BHB has lower developed reserves of oil and gas than many other regions; however, our study supports findings from other studies that demonstrate energy development increases lek abandonment. Our findings indicate conservation efforts should be focused on minimizing well development and implementing wildfire suppression tactics near active sage‐grouse leks. © 2012 The Wildlife Society.

Wyoming big sagebrush (Artemisia tridentata wyomingensis) treatments are often implemented to improve breeding habitat for greater sage‐grouse (Centrocercus urophasianus), a species of considerable conservation concern. In 2008 and 2009, we measured vegetation structure available to sage‐grouse for breeding at 19 sites that were prescribed burned during 1990–1999 and 2000–2006, 6 sites that were mowed during 2000–2006, and 25 paired, untreated reference sites in the Bighorn Basin of north‐central Wyoming, USA. We compared minimum guidelines for canopy cover and height of Wyoming big sagebrush and perennial grass in arid greater sage‐grouse breeding habitat (Connelly et al. 2000b) to measurements at our sampling sites. Sagebrush canopy cover and height at reference sites met the minimum guidelines. Sagebrush canopy cover at burned and mowed sites did not meet the minimum guideline, except for sites mowed on aridic soils measured during 2009. Burned and mowed (3 of 4 cases) sagebrush did not meet minimum height for breeding up to 19 yr and 9 yr post‐treatment, respectively. Perennial grass canopy cover and height met the minimum guidelines for breeding habitat at reference, burned, and mowed sites. Burning increased grass canopy cover, but not height, compared to reference sites in 2 of 8 instances. Because burning, but not mowing, infrequently enhanced grass cover, but not height, and sagebrush structure was reduced by both practices for long periods, managers should consider how treatments may negatively affect Wyoming big sagebrush communities for sage‐grouse and consider other practices, including continued nontreatment and improved livestock grazing, to increase grass cover and height. © 2012 The Wildlife Society.

Common raven (Corvus corax; hereafter “raven”) populations have increased dramatically in the western United States in recent years. Ravens benefit from human resources and are known predators of other avian species. We developed a raven study to determine how primary (large‐scale, high food density, and temporally consistent) anthropogenic subsidies influenced raven movement and space use during the raven and greater sage‐grouse (Centrocercus urophasianus) breeding season and within sagebrush habitat that is commonly used by greater sage‐grouse. We also examined how movement, space use, and anthropogenic subsidization differed among ravens in different breeding statuses. We hypothesized that breeding ravens would use small areas around their nest and that nonbreeding ravens would range widely in search of food. We expected that breeding ravens would frequently use anthropogenic structures and that both breeding and nonbreeding ravens would regularly visit primary point‐source subsidies (e.g., landfills and transfer stations). Twenty ravens were captured and GPS‐tagged between 2012 and 2014. We found that breeding ravens overwhelmingly built nests on anthropogenic structures (96–100%) and subsequently used small portions of the landscape intensively. Movement of nonbreeding ravens (distance average = 2783 m/h) and ravens who had failed nests (distance average = 1357 m/h) ranged widely. Breeding ravens visited highways and railroads inversely proportional to the distance between the nest and the nearest highway/railroad. Nonbreeding ravens regularly visited landfills and transfer stations, but breeding ravens did not (<0.1% of locations). We found that nonbreeding ravens travel widely to utilize primary point‐source subsidies, breeding ravens focus on areas near the nest, and ravens with failed nests switch to movement behaviors and space use similar to wide‐ranging nonbreeding ravens. These findings have implications for the management of ravens and anthropogenic subsidies in sagebrush landscapes to potentially reduce depredation of greater sage‐grouse nests.

Wyoming big sagebrush (Artemisia tridentata wyomingensis A. t. Nutt. ssp. wyomingensis Beetle and Young) communities provide structure and forbs and insects needed by greater sage-grouse (Centrocercus urophasianus) for growth and survival. We evaluated forb, insect, and soil responses at six mowed and 19 prescribed burned sites compared to 25, paired and untreated reference sites. Sites were classified by treatment type, soil type, season, and decade of treatment (sites burned during 1990-1999 and sites burned or mowed during 2000-2006). Our objective was to evaluate differences in ten habitat attributes known to influence sage-grouse nesting and brood rearing to compare responses among treatment scenarios. Contrary to desired outcomes, treating Wyoming big sagebrush through prescribed burning or mowing may not stimulate cover or increase nutrition in food forbs, or increase insect abundance or indicators of soil quality compared with reference sites. In some cases, prescribed burning showed positive results compared with mowing such as greater forb crude protein content (%), ant (Hymenoptera; no./trap), beetle (Coleoptera/no./trap), and grasshopper abundance (Orthoptera; no./sweep), and total (%) soil carbon and nitrogen, but of these attributes, only grasshopper abundance was enhanced at burned sites compared with reference sites in 2008. Mowing did not promote a statistically significant increase in sage-grouse nesting or early brood-rearing habitat attributes such as cover or nutritional quality of food forbs, or counts of ants, beetles, or grasshoppers compared with reference sites.

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