Effects of forest characteristics on ruffed grouse nesting ecology in central Maine, USA

Effective wildlife management requires a broad understanding of how forest structure and composition influence habitat use and vital rates during all aspects of species' life-cycles, however habitat characteristics may have variable importance during different life phases. Even though the ruffed grouse Bonasa umbellus is a popular game bird that has long been a focal species for management, a greater understanding of the links between forest characteristics and components of ruffed grouse reproduction would enhance managers' ability to promote the species. We monitored 45 nests belonging to 37 females during 2015-2017 in central Maine, USA, and evaluated the influence of forest characteristics on nest-site selection, nest survival and female survival while nesting. Ruffed grouse females selected nest sites with greater horizontal visual obstruction (beta = 0.16 +/- 0.06 85% CI) than found at other sites that were locally available to them, however this characteristic did not appear to improve nest survival or female survival while nesting. Cumulative nest success was 42.8% and daily nest survival was reduced when coarse woody debris (CWD) was present at nest sites (beta = -0.41 +/- 0.33 85% CI), but we found no evidence that other habitat characteristics or features of nests themselves were related to nest survival. However, reduced female survival while nesting was associated with presence of CWD (beta = -1.27 +/- 0.91 85% CI), greater tree basal area (beta = -0.96 +/- 0.81 85% CI) and greater conifer stem density (beta = -0.45 +/- 0.28 85% CI) at nest sites; females had a 74.4% chance of survival during the length of time required to successfully nest. Our results demonstrate the importance of forest characteristics on multiple components of species' nesting ecology, and we provided management suggestions to promote attractive ruffed grouse nesting habitat while potentially mitigating sources of nesting failure.