GREATER SAGE-GROUSE IN A GRAZED LANDSCAPE: HABITAT SELECTION, DEMOGRAPHIC RATES, AND POPULATION TRENDS IN CENTRAL MONTANA

Greater sage-grouse (Centrocercus urophasianus) abundance has declined across the species’ range due to habitat loss, degradation, and fragmentation. To address this decline, information is needed to guide habitat conservation priorities and population management efforts. This includes information about patterns of habitat selection at multiple spatial scales, habitat and land use variables that affect demographic rates, and population trend estimates. We collected ten years of data (2011-2020) on sage-grouse demographic rates and habitat selection, as well as on vegetation and livestock grazing patterns, to address these topics. We were specifically interested in the effects of a rotational grazing system implemented through the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Sage Grouse Initiative (SGI). In Chapter 1, we investigated whether sage-grouse hens select seasonal home ranges based on topographic, grazing, and vegetation variables. We found that hens select for shrub cover across all seasons, with seasonal differences in other variables. We also found that sage-grouse located within livestock pastures select for areas with higher used animal unit months (“used AUMs,” or a measure of the amount of forage grazed) in addition to shrub cover. In Chapter 2, we evaluated the effects of the SGI rotational grazing system on sage-grouse nest success. We found that neither SGI rotational grazing systems nor other indices of livestock use had measurable effects on nest success, but we saw a very minor positive effect of senesced grass height. The majority of interand intra-annual variation in nest success was unexplained by grazing-related variables. Taken together, these results suggest that the patterns of land use and livestock management observed during the study are not affecting sage-grouse in this study area, as there is no evidence for a negative effect of livestock grazing on estimated demographic rates or habit