Abstract
Understanding selection of breeding habitat is critical to conserving and restoring habitats for the Greater Sage-Grouse (Centrocercus urophasianus), particularly in xeric landscapes (≤25 cm annual precipitation). We monitored radio-marked female sage-grouse in south-central Wyoming in 2008 and 2009 to assess microhabitat use during nesting and brood rearing. For each model we grouped variables into three hypothesis sets on the basis of the weight of support from previous research (a priori information). We used binary logistic regression to compare habitat used by grouse to that at random locations and used an information-theoretic approach to identify the best-supported models. Selection of microhabitat for nests was more positively correlated with mountain big sagebrush (Artemisia tridentata vaseyana) than with Wyoming big sagebrush (A. t. wyomingensis) and negatively correlated with cheatgrass. Nesting hens also selected microhabitats with greater litter cover. Microhabitat for brood-rearing had more perennial grass and sagebrush cover than did random locations. Microhabitat variables most supported in the literature, such as forb cover and perennial grass cover, accounted for only 8% and 16% of the pure variation in our models for early and late brood rearing, respectively. Our findings suggest sage-grouse inhabiting xeric sagebrush habitats rely on sagebrush cover and grass structure for nesting as well as brood-rearing and that at the microhabitat scale these structural characteristics may be more important than forb availability. Therefore, in xeric sagebrush, practices designed to increase forb production by markedly reducing sagebrush cover, as a means to increase sage-grouse productivity, may not be justified.
Highlights
Quantity and quality of breeding habitat have been suggested as the most important factors dictating the productivity of greater sage-grouse (Centrocercus urophasianus; hereafter, sagegrouse) populations [1,2,3]
The purpose of our study was to use microhabitat data collected over a broad range of sagebrush habitats in Wyoming to 1) identify microhabitat characteristics that influence sage-grouse selection of nest sites, 2) compare available microhabitat within and outside of Core Areas, 3) compare microhabitat used by sagegrouse for nesting between areas protected and not protected under the Core Area Policy, and 4) evaluate the influence of microhabitat on nest success and compare nest success within and outside of Core Areas
Model averaging indicated that the 95% confidence interval for the odds ratio estimate of Gap3m, PerGrass_H, Grass5m, Forb1m, BioCrust5m, and Litter5m overlapped 1 (Table 4); we considered those to be marginal predictor variables and limited our interpretations to primarily focus on the Shrub1m, Artr2.5m, Artr_H, Gap0.5m, V0, and BareRock5m variables
Summary
Quantity and quality of breeding habitat have been suggested as the most important factors dictating the productivity of greater sage-grouse (Centrocercus urophasianus; hereafter, sagegrouse) populations [1,2,3]. Studies have reported that sage-grouse select nest sites based on a preference for different microhabitat characteristics, such as sagebrush density [4,5], sagebrush cover [6,7], shrub height [8], grass height [7,8,9], and grass cover [7,10]. These studies all indicated that sage-grouse choose nest locations in habitats with greater concealment cover. Studies across broader ranges and more diverse microhabitat have the greatest potential to identify microhabitat variables that influence nest selection and success of sage-grouse at regional scales
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