Effects of conifer expansion on greater sage-grouse nesting habitat selection

Expansion of conifer woodlands into sagebrush (Artemisia spp.) ecosystems is a primary threat to the greater sage-grouse (Centrocercus urophasianus) in the Great Basin, southeast Oregon, USA. Conifer removal to restore sage-grouse habitats has been widely implemented, yet limited information exists on the effects of conifer expansion on sage-grouse habitat selection. Our objective was to evaluate the landscape-scale effects of conifer expansion on selection of sites for nesting and to estimate direction, magnitude, and scale of effects. We classified 160 nests and 167 available sites with random forests during 2010–2011 to assess effects of conifer cover and tree clustering at multiple scales along with other vegetation and topographic covariates on selection of nesting habitat. Relative probability of nesting was negatively associated with >3% conifer cover within 800 m of nests. When trees were present within 800 m of nests, sage-grouse nested where trees were clustered rather than dispersed, suggesting selection for more open habitat. Results further indicated that sage-grouse are nesting in landscapes susceptible to conifer expansion that have yet to be invaded. Sage-grouse are expected to lose nesting habitat as conifer expansion continues, but management intervention may be a possible solution to increase habitat availability where open space for nesting is a limiting factor.