Seasonal Micro-Habitat Relationships of Ruffed Grouse in Southeastern Idaho

Abstract

We summarized characteristics of micro-habitats selected by ruffed grouse (Bonasa umbellus) in southeastern Idaho for all seasons. Ruffed grouse preferred stands dominated by quaking aspen (Populus tremuloides). Drumming sites selected by males were typified by high vegetation density. Brood hens selected relatively open areas with high cover of herbaceous vegetation. Drumming sites differed (P 2,130 m): quaking aspen, aspen/conifer mixed, dense conifer, and open conifer. A description of each of the vegetation types is in Stauffer and Peterson (1985). Size of stands in each cover type ranged from 23 cm dbh/ha 35 (17) 86 (31) 12 (8) 73 (38) Maple/ha 300 (82) 0 (-) 94 (76) 9 (9) a Sample size. b Standard error. >200 ha. Cover types generally were well interspersed throughout the study area. We spent 1,593 hours (spring, 322 hours; summer, 543 hours; autumn, 296 hours; winter, 432 hours) searching for grouse from May 1979 through May 1981. At these times, an area comprising one or a few vegetation types was selected and thoroughly searched. Searching effort was distributed among each vegetation type in approximate proportion to the type's occurrence on the study area. Locations of grouse flushes were used as the center of a 0.01-ha circular plot for which we recorded (Noon 1981): percent of area within 40 m of the plot center that was comprised of coniferous or deciduous cover or open; percent tree canopy and ground canopy cover; canopy height and average height of herbaceous vegetation; number of woody stems 69 cm); slope; aspect; and vegetation type. Counts of woody stems and trees were converted to number per ha. Additional data recorded at drumming sites included drumming log diameter and length and an ocular estimate of the percent of five strata (0-0.5 m, 0.51-1.5 m, 1.51-3.0 m, 3.01-6.0 m, >6.0 m) with vegetation. Means for data recorded in the 0.01-ha plots at grouse locations were calculated for various combinations of vegetation type and season to describe the characteristics of sites selected. We used Hotelling's T2 and multivariate analysis of variance (MANOVA, Morrison 1976) to test hypotheses of no difference in habitat use by groups of grouse as described in the objectives. We established 150 random plots to sample habitat characteristics assumed available to grouse in aspen and aspen/conifer stands, which were preferred vegetation types (Stauffer and Peterson 1985). Random plot data were subjected to a principal components analysis (Morrison 1976) to reduce the set of correlated variables to independent components that represented habitat gradients occurring within aspen and aspen/conifer stands. We then assigned observations of ruffed grouse in aspen and aspen/conifer vegetation scores on each of the habitat gradients to compare characteristics of microhabitats where we observed ruffed grouse to what was available. Appropriate transformations (log, square-root, or arc-sine) were applied to non-normal variables. RESULTS AND DISCUSSION Ruffed grouse exhibited a preference for sites dominated by aspen (Stauffer and Peterson 1985), thus only data from grouse observations in aspen and aspen/conifer stands (N = 207) are presented here.