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Greater Sage-Grouse Research



Nest Site Selection Project

Introduction: Loss of nesting habitat is believed to be a factor in the decline of Greater sage-grouse (Centrocercus urophasianus) throughout their range.  Few data are available for sage-grouse in Mono County, California, in the southwestern most portion of the species’ range.
Methods: We studied habitat selection of nesting sage-grouse in Mono County, California, from 2003 to 2005 by capturing and radio tracking females to identify nesting locations.  We sampled vegetation at nest sites and randomly selected sites within 200 m of nests and within each of five subareas within Mono County.
Findings: Nest sites were characterized by 42.4 % ± 1.3 (± SE) shrub canopy cover, 10.5 cm ± 1.0 cm residual grass height, and 2.7 ± 1.0 % residual grass cover.  Shrub cover was the only variable found to differentiate nest sites from randomly selected sites.  Unlike some other studies, we did not find understory vegetation to be important for selecting nest sites.  Mean shrub cover was 38.7 ± 1.5 % at random sites within 200 m of nests and  33.6 ± 1.6 % at random sites at the approximate scale of home ranges, indicating that nesting females selected nesting areas that contained denser shrubs than their home range, and nest sites that contained greater shrub cover than the vicinity immediately surrounding nests. 
Implications: Our results suggest that managers should consider managing for greater shrub cover in Mono County than what is currently called for in other parts of sage-grouse range and that management for sage-grouse habitat may need to be tied more closely to local conditions.

Nest success 
Sagebrush Landscape2 
Nest Site

Nest Survival Project

Introduction: We studied nest survival of sage-grouse in five subareas of Mono County, California from 2003 to 2005.
Methods: We captured and radio-tracked females (n=72) to identify nest sites and monitor nest survival.  We measured vegetation at nest sites and within a 10 m radius area around each nest to evaluate possible vegetation factors influencing nest survival.  We estimated daily nest survival and the effect of explanatory variables on daily nest survival using nest survival models in Program MARK.  We assessed effects on daily nest survival of total, sagebrush (Artemisia spp.), and non-sagebrush live shrub cover, Robel visual obstruction, the mean of grass residual height and grass residual cover measurements within 10 m of the nest shrub, and area of the shrub, shrub height, and shrub type at the nest site itself.
Findings: Our nest survival estimate, assuming a 38 day exposure period, was 43.4 %, and percent cover of shrubs other than sagebrush was the variable most related to nest survival.  Nest survival increased with increasing cover of shrubs other than sagebrush.  Also, daily nest survival decreased with nest age, and there was considerable variation in nest survival among the five subareas.
Implications: A diversity of shrub species within sagebrush habitats may be important to sage-grouse nest success in Mono County.

Abandoned Nest 
Abandoned Nest
 Successful Hatch
Successfully Hatched Eggs from Nest

Nest Predation Project

Introduction: Nest predation is a natural component of greater sage-grouse (Centrocercus urophasianus) reproduction, but changes in nesting habitat and predator communities may adversely affect grouse populations.
Methods: We used a 2-part approach to investigate sage-grouse nest predation. First, we used information criteria to compare nest survival models that included indices of raven abundance with other survival models that consisted of day of incubation, grouse age, and nest microhabitat covariates using measurements from 77 of 87 sage-grouse nests. Second, we used video monitoring at a subsample of 55 of 87 nests to identify predators of depredated nests (n = 16) and evaluated the influence of microhabitat factors on the probability of predation by each predator species.
Findings: The most parsimonious model for nest survival consisted of an interaction between day of incubation and abundance of common ravens (Corvus corax; wraven × incubation day = 0.67). An estimated increase in one raven per 10-km transect survey was associated with a 7.4% increase in the odds of nest failure. Nest survival was relatively lower in early stages of incubation, and this effect was strengthened with increased raven numbers. Using video monitoring, we found the probability of raven predation increased with reduced shrub canopy cover. Also, we found differences in shrub canopy cover and understory visual obstruction between nests depredated by ravens and nests depredated by American badgers (Taxidea taxus).
Implications: Increased raven numbers have negative effects on sage-grouse nest survival, especially in areas with relatively low shrub canopy cover. We encourage wildlife managers to reduce interactions between ravens and nesting sage-grouse by managing raven populations and restoring and maintaining shrub canopy cover in sage-grouse nesting areas.

Raven Perched on Telephone Pole. 
Coates/ Delehanty

Sage-Grouse Brood Survival Project

Introduction: Examining links between the fitness of individual organisms and their habitat-based decisions is useful to identify key resources for conservation and management of a species, especially at multiple spatial scales because selection of habitat attributes may vary with spatial scale. Decisions of habitat use by brood-rearing Greater Sage-Grouse (Centrocercus urophasianus) may influence the survival of chicks.
Methods: We conducted radio-telemetry on 38 sage-grouse broods within Mono County, California during 2003–2005. At relocation and random sites, we measured habitat characteristics at three spatial scales using field procedures (scale, 0.03 ha) and Geographical Information System tools (scales, 7.9 ha and 226.8 ha). We then conducted three data analyses using an information-theoretic modeling approach. The purpose of these analyses was to: (1) identify habitat factors that were selected (defined as use disproportionate to availability) by sage-grouse broods; (2) identify habitat factors associated with brood success (defined as ³1 live chick at 50 days post-hatch; 24 were successful, 14 unsuccessful); and (3) evaluate brood success as a function of habitat selection indices for brood-rearing sage-grouse.
Findings: At the smallest spatial scale (0.03 ha), grouse with broods selected areas with greater perennial forbs and higher richness of plant species. At larger scales (7.9 ha and 226.8 ha), areas encroached by Utah juniper (Juniperus osteosperma) and single leaf pinyon pine (Pinus monophylla) were avoided by grouse. Most importantly, the probability of fledging a brood increased as sage-grouse females selected habitats with greater densities of perennial forbs (0.03 ha) and higher meadow edge (perimeter to edge ratio; 7.9 ha), perhaps because these areas provided a balance of food and protective cover for chicks.
Implications: These results suggest that managers should discourage tree encroachment and preserve and enhance sagebrush stands interspersed with perennial forbs and a mixture of small upland meadows.

Female Grouse with Radio Collar
Greater Sage Grouse Chick 
Greater Sage-Grouse Chicks (3)
 spatial analysis
Vegetation Classificaton for Analysis

Sage-Grouse Survival and Habitat Project

Introduction: Greater sage-grouse populations have declined throughout their range in North America. Mono Basin sage-grouse populations has been determined to be a distinct population segment by U.S. Fish and Wildlife Service. We examined land cover use in relation to survival by including proportion of land cover type used by sage-grouse as individual time-varying covariates.
Methods: We captured and placed radio collars on n = 29 males, and n = 110 female sage-grouse during the spring and fall of 2003-2005. We relocated the radio-collared grouse at least 2 or more times per week for 32 months. Individual land cover use, age, sex, and spatial variation was related to survival.
Findings: Top group models – included spatial variation between sub-areas and age, accounting for 90% of AICc weights. Survival rates were highest during winter and lowest during summer seasons. Adults had lower survival rates than yearlings, especially males. Sub-adults are less conspicuous, increasing the probability of survival than adults.
Implications: Land-management practices should include reducing the encroachment of forest and non-sagebrush dominated shrub lands into sage-grouse habitat. Effects of habitat patch configurations at the landscape-level on sage-grouse fitness will provide additional insight into best management practices for sage-grouse.

Mel grouse bistate
Melissa with Sage-grouse 
Matt Telemetry, bistate
Radio-Telemetry to Locate Tagged Grouse 
Mortality of tagged sage-grouse 

Pinyon/ Juniper Encroachment Project

Introduction: The range of pinyon pine and juniper woodland expansion into the sagebrush ecosystem has increased 10-fold since the 1800’s and is thought to adversely affect sage-grouse populations. We identified spatial scale at which sage-grouse avoid sagebrush/tree areas (MST; phase I encroachment) and examined sources of variation by age, sex, and season.
Methods: We captured greater sage-grouse at four study areas between 2002 – 2005 and placed radio-transmitters to be able to relocate each individual grouse. Three parts were examined: disproportionate use to availability, sources of variation in use, and patch size analysis.
Findings: Sage-grouse avoided MST (≤ 40 trees/ha) at both scales but the larger scale had greater support. Yearling grouse varied seasonally in their avoidance behavior and differed from adults. Avoidance of MST was most supported when patch widths exceeded 200m.
Implications: Management directed at preventing the width of a patch that consists of a relatively low tree density from exceeding > 200 m will likely reduce avoidance behavior of those areas by grouse. Further studies that focus on variation in tree density within patches would be beneficial.

Sagebrush Steppe
Pinyon and Juniper Encroachment into Sagebrush Habitat.

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