Ruffed grouse selection of drumming sites in the Black Hills National Forest

Ruffed grouse (Bonasa umbellus) are important game birds that depend on multiple forest age-classes of aspen (Populus spp.) for food and cover, which makes them an appropriate management indicator species for the condition of quaking aspen (Populus tremuloides) communities in the Black Hills National Forest of western South Dakota and northeastern Wyoming (BHNF). Recent landscape-scale drumming surveys showed that occupancy of ruffed grouse in the BHNF depended primarily on the amount of aspen-dominated vegetation within a 95 ha site. However, an investigation of drumming site characteristics is lacking. To evaluate drumming site selection, we located and measured the drumming structure and surrounding vegetation for 49 primary drumming sites and 147 paired unused sites during 2007 and 2008. We used discrete-choice modeling with an information-theoretic approach to evaluate resource characteristics of drumming sites associated with use. Percent area exposed (visibility) between 0.9 m and 1.8 m in height around the drumming structure had a negative, exponential relationship with drumming site selection and the combined density of woody and herbaceous plants ≥1-m tall with a stem diameter <2.54 cm had a positive, asymptotic relationship with site selection. Reducing the visibility between 0.9 m and 1.8 m around the structure from 40% to 0% increased the relative probability of selection of drumming sites 9-fold. Increasing the density of woody and herbaceous stems from 8000 stems/hectare to 24,000 stems/hectare increased the relative probability of selection 20-fold. The selection of drumming sites with a high density of vegetation ≥1 m in height and low visibility between 0.9 m and 1.8 m suggests ruffed grouse select drumming sites that might reduce the chances of predation. Thus, management actions to improve ruffed grouse breeding habitat should focus on increasing the density of vegetation cover ≥1 m in height.