Nesting Ecology of Greater Sage-Grouse Centrocercus urophasianus at the Eastern Edge of their Historic Distribution

Greater sage-grouse Centrocercus urophasianus populations in North Dakota declined approximately 67% between 1965 and 2003, and the species is listed as a Priority Level 1 Species of Special Concern by the North Dakota Game and Fish Department. The habitat and ecology of the species at the eastern edge of its historical range is largely unknown. We investigated nest site selection by greater sage-grouse and nest survival in North Dakota during 2005 - 2006. Sage-grouse selected nest sites in sagebrush Artemisia spp. with more total vegetative cover, greater sagebrush density, and greater 1-m visual obstruction from the nest than at random sites. Height of grass and shrub (sagebrush) at nest sites were shorter than at random sites, because areas where sagebrush was common were sites in low seral condition or dense clay or clay-pan soils with low productivity. Constant survival estimates of incubated nests were 33% in 2005 and 30% in 2006. Variables that described the resource selection function for nests were not those that modeled nest survival. Nest survival was positively influenced by percentage of shrub (sagebrush) cover and grass height. Daily nest survival decreased substantially when percentage of shrub cover declined below about 9% and when grass heights were less than about 16 cm. Daily nest survival rates decreased with increased daily precipitation

Nesting and Brood-Rearing Habitat Selection of Greater Sage-Grouse and Associated Survival of Hens and Broods at the Edge of Their Historic Distribution

Greater sage-grouse (Centrocercus urophasianus) once occurred in 12 states and 3 Canadian provinces. Sage-grouse populations have declined over the last 60 years due to extensive habitat alteration and loss. Concerns for the management and conservation of greater sage-grouse and their habitats have resulted in petitions to list them under the Endangered Species Act. In North Dakota, sage-grouse are confined to approximately 800 square miles of sagebrush habitat, which is facing severe habitat fragmentation and habitat loss. Sage-grouse in North Dakota are not isolated, but are contiguous with populations in Montana and South Dakota. Annual rates of change suggest a long-term population decline in North Dakota, declining 2.79% per year from 1965 to 2003. The species is listed as a Priority Level 1 Species of Special Concern in the state. The objectives of this study were to estimate nest survival, hen and brood survival, and associated nest and brood-site habitat selection of sage-grouse in southwestern North Dakota. The study was conducted during the spring and summer of 2005 and 2006 in Bowman County, North Dakota. Nest-sites were monitored to determine nest fate and broods were monitored by tracking radio-marked adults that successfully hatched young. Habitat selection was characterized by comparing vegetation at nest-sites and brood-sites to vegetation points at randomly selected sites. I found 34 nests from 39 female sage-grouse (21 in 2005, 18 in 2006) that were radio-marked. Vegetation measurements were taken at 34 nest-sites and 50 random points. I collected vegetation measurements from 130 brood-sites and 107 random sites. Nest survival averaged 31% (33% in 2005 and 30% in 2006). The best model of nest survival included daily precipitation. Models that contained percent grass cover and grass height from the Robel pole also had substantial support (i.e., \u3c 2 AIC units) to explain nest survival. One model strongly supported characteristics associated with selection of nest-sites that included percent total cover, 1-m VOR, and sagebrush density. Sage-grouse nests were positively associated with more total cover, 1-m VOR, and sagebrush density than were present at random sites. In 2005, hen survival was 84% (95%CI: 0.67 to 1.00, n = 20) from capture date through the brood-rearing season, and 60% (95%CI: 0.44 to 0.76, n = 39) in 2006. I monitored 7 broods in 2005, with an average of 6.86 ± 0.95 chicks/hen at hatch. At 3 weeks post hatch, the average brood size was 2.34 chicks/hen representing 34% apparent survival. In 2006, 6 broods averaged 6.67 ± 1.03 chicks/hen at hatch. At 3 weeks post hatch, the average brood size was 2.83 chicks/hen representing 42% apparent survival. A total of 38 sage-grouse chicks were radio-marked (13 in 2005, and 25 in 2006). Chick survival from hatch date to 3 weeks post hatch, combined with those that survived to 5-6 weeks of age and were able to be captured, 17% of the chicks were estimated to recruit into the population in December 2005 and 13% in December 2006. The majority of identifiable predation events on radio-marked sage-grouse chicks were from canids. One model of brood site selection was positively associated with more total forb, total grass, and total sagebrush than was present at randomly selected sites, and negatively associated to percent bareground, sagebrush height and sagebrush width. Brood sites consisted of 6-16% forb cover, 29-34 % grass cover, 5% sagebrush cover and approximately 30-38 cm tall sagebrush plants, and 50-53 cm wide sagebrush plants. Percent bareground cover consisted of 11-25% at brood sites. I recommend that managers develop strategies to preserve the integrity of shrubsteppe habitat in southwestern North Dakota. Herbaceous cover in sagebrush habitats is an important component of nesting and brood-rearing habitat for sage-grouse. Thus I recommend management activities that maintain or restore dense, taller residual grass within sage-grouse habitat