Abstract
The purpose of our study was to identify microhabitat characteristics of greater sage-grouse (Centrocercus urophasianus) nest site selection and survival to determine the quality of sage-grouse habitat in 5 regions of central and southwest Wyoming associated with Wyoming’s Core Area Policy. Wyoming’s Core Area Policy was enacted in 2008 to reduce human disturbance near the greatest densities of sage-grouse. Our analyses aimed to assess sage-grouse nest selection and success at multiple micro-spatial scales. We obtained microhabitat data from 928 sage-grouse nest locations and 819 random microhabitat locations from 2008–2014. Nest success was estimated from 924 nests with survival data. Sage-grouse selected nests with greater sagebrush cover and height, visual obstruction, and number of small gaps between shrubs (gap size ≥0.5 m and <1.0 m), while selecting for less bare ground and rock. With the exception of more small gaps between shrubs, we did not find any differences in availability of these microhabitat characteristics between locations within and outside of Core Areas. In addition, we found little supporting evidence that sage-grouse were selecting different nest sites in Core Areas relative to areas outside of Core. The Kaplan-Meier nest success estimate for a 27-day incubation period was 42.0% (95% CI: 38.4–45.9%). Risk of nest failure was negatively associated with greater rock and more medium-sized gaps between shrubs (gap size ≥2.0 m and <3.0 m). Within our study areas, Wyoming’s Core Areas did not have differing microhabitat quality compared to outside of Core Areas. The close proximity of our locations within and outside of Core Areas likely explained our lack of finding differences in microhabitat quality among locations within these landscapes. However, the Core Area Policy is most likely to conserve high quality habitat at larger spatial scales, which over decades may have cascading effects on microhabitat quality available between areas within and outside of Core Areas.
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]
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
Model averaging indicated that the 95% confidence interval for the odds ratio estimates of Gap0.5m, AnGrass, Bare5m, and Rock5m overlapped 1 (Table 4); we considered those to be marginal predictor 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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