Population dynamics, habitat use and movements of greater sage-grouse in Moffat County, Colorado

Long-term declines in greater sage-grouse (Centrocercus urophasianus) abundance may be associated with low productivity due to habitat degradation. Therefore, I investigated the effects of vegetation characteristics on nest site selection and success, and created predictive models using forward stepwise logistic regression. Greater sage-grouse nested in sites having greater sagebrush canopy cover, nest shrub height and visual obstruction than random sites. Forb cover was greater at nest sites than random but grass cover and % exotic species at the nest bowl were greater at random sites than nest sites. Nest success was high with 58% (n = I08) of hens hatching 2: 1 egg. Nest success was positively associated with plant species richness, percent sagebrush, grass and forb cover and negatively associated with exotic herbaceous cover. Additionally, grass heights measured at the nest bowl and at I m from the nest bowl were parameters associated with nest success. Vegetation was reduced in 2002, a year with less spring precipitation, and may be associated with lower nest success. Habitat management to encourage greater sage-grouse nest success should promote native herbaceous understory growth in April and May and discourage sagebrush removal. Habitat management guidelines are based, in part, on studies of greater sage-grouse nest site selection, which measure habitat characteristics post-hatch,> 30 days after initiation. Thus, these recommendations may be flawed due to the time lag in sampling. I investigated differences in habitat at initiation versus hatch using previous year's nest sites. A randomized complete block MANOV A indicated differences based on timing of sampling. The difference was largely due to grass height and percent grass cover. Grass heights at the nest bowl and at 1 m were 10 cm and 9 cm at initiation and I6 cm and I3 cm at hatch, respectively. Percent grass cover of the sample plot increased from 4 to 6% cover from initiation to hatch. Sampling techniques conducted at hatch sufficiently describes nest site habitat at selection apart from grass heights and grass cover. Despite extensive research into the habitat requirements of greater sage-grouse, summer night-roosting habitat has received no attention. Therefore, I investigated the vegetation characteristics of brood and night roost selection arid compared diurnal and nocturnal habitat use and selection. Predictive models were created using forward stepwise logistic regression. Greater sage-grouse selected brood-use areas with greater visual obstruction, greater forb cover and less bare ground than random. Night-roost locations were characterized by less bare ground and visual obstruction but greater percent forb cover than at random sites. Mean shrub cover and shrub height at night roost locations was lower (9% vs. 22%) and shorter (31 vs. 58 cm) than at brood sites. Forb cover was an important predictor of both diurnal and nocturnal habitat use but did not meet the minimum requirements of 2: 1 Oo/o suggested by management guidelines. Current habitat management guidelines attend only to diurnal habitat needs and should be revised in order to address the variance in temporal habitat selection. I described home range, daily movements and survival of greater sage-grouse monthly, seasonally and annually. Median daily movement during the brood-rearing period was greater for females with broods (184m/day) than those without broods (103m/day), and was not associated with chicks/female at 6 weeks post-hatch. Lek to nest distance and brood home range sizes were greater for females that nested in the Axial Basin (4.6 km, 1,151 ha) than the Danforth Hills (2.6 km, 439 ha) indicating that habitat conditions may be causing greater movement in the Axial Basin. Distances moved from the last diurnal location to night roost sites (397m) suggested that females with broods were required to move 2 times their median daily movement in order to find suitable night-roost habitat and that seasonal movement estimates in the literature may be biased low. Annual home range sizes of yearlings and adults, and seasonal movements from the lek of capture indicated that the population of greater sage-grouse in the Axial Basin and Danforth Hills was non-migratory. Annual survival rates were greater for yearling (7 5%) than adult females (57%). Year, seasonal trend and age were variables that contributed to predictive annual survival models. Survival rates were lowest in the breeding and brood-rearing periods and increased through the fall and winter. Body condition indices, serum chemical constituents and disease prevalence were estimated for pre-laying female greater sage-grouse. Previous studies conjectured prematernal diet was associated with greater•sage-grouse productivity and survival but gave no specifics on condition with respect to body size or serum biochemical constituents. Thus I investigated pre-breeding body condition as a function of a body condition index and a serum chemical panel and how these parameters were associated with reproduction and survival. No differences were found in measures of fecundity, however the expense may be incurred through survival rates, which were related to the body condition index, serum protein and uric acid concentrations. Baseline biochemistry reference ranges for pre-breeding hens were established. These values varied by year and capture technique. Annual variation may be linked to precipitation and forage quality. Elevated creatinine kinase and chloride levels occurred in females captured by the CODA net-launcher in comparison to females captured by night-spotlighting. Differential biochemical values may have been caused by stress or diurnal variation in serum chemistry. Diseases tested included avian influenza, Salmonella pullorum/ S. typhoid, Mycoplasma gallisepticum, M. synoviae, and M meleagridis. Individual grouse tested positive for M. synoviae, however there was no consistency of lab results among years, laboratories, or blood storage method. Additionally, no relationship between disease occurrence and reproduction or survival was detected and false positives have been reported with the plate agglutination-screening test. Given this information, the serology results need to be viewed cautiously as they were based on questionable disease incidence.