Ruffed Grouse Selection of Drumming Sites in the Black Hills National Forest

Article excerpt

ABSTRACT.-

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.

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INTRODUCTION

Ruffed grouse (Bonasa umbellus) are the management indicator species for the condition of quaking aspen (Populus lremuloides) in the Black Hills National Forest of western South Dakota and northeastern Wyoming (BHNF; U.S. Forest Service, 1997) because of their dependence on multiple age-classes of aspen (Populus spp.) for food and cover (Bump et al, 1947; Gullion and Svoboda, 1972; Kubisiak, 1985, 1989). Given their status and popularity as a game bird, there has been interest by the U.S. Forest Service and South Dakota Department of Game, Fish and Parks to assess the status of ruffed grouse in the Black Hills and develop greater knowledge of the vegetative features that influence ruffed grouse occurrence. Recent ruffed grouse drumming surveys showed that the probability of ruffed grouse occupying a sample site (550-m buffer surrounding the survey point) was positively associated with the amount of aspen-dominated vegetation within the site (Hansen, 2009). Results from that study describe ruffed grouse selection of dominant vegetation types at a landscape scale (95 ha), but do not consider micro-site vegetation attributes that might also influence selection.

During the spring, male ruffed grouse "drum" on elevated structures, such as fallen logs, stumps and rocks to attract females and maintain their territory (Bump et al, 1947). Thus, characteristics of the drumming structure (e.g., height, diameter, length) and the adjacent vegetation (e.g., stem density, basal area, visibility, overstory canopy cover) might be important in the selection of drumming sites. Studies investigating the selection of ruffed grouse drumming sites throughout the United States and Canada have found that selection is positively correlated with the amount of understory cover (Stoll et al, 1979; Palmer, 1963; Thompson et al, 1987; Stauffer and Peterson, 1985; Buhler and Anderson, 2001). However, not all studies agree that drumming structure characteristics affect ruffed grouse site selection of drumming sites. …