Anthony D. Apa

Sage grouse use of nest sites in southeastern Idaho

We investigated nest site selection by sage grouse (Centrocercus urophasianus) in southeastern Idaho from 1987 to 1989. During 3 breeding seasons, 79% of 84 nest sites were found under sagebrush (Artemisia spp.). Nest success averaged 53% for grouse that used sagebrush and 22% for birds that used nonsagebrush nest sites. Total vegetative cover for sagebrush and nonsagebrush nest sites was similar. However, grass height was shorter (P = 0.01) at sagebrush compared to nonsagebrush nest sites. Herbaceous cover was important to nesting sage grouse but the relatively low nest success of nonsagebrush nest sites indicated they might provide less than optimal nesting habitat. J. WILDL. MANAGE. 55(3):521-524 Most studies that have examined sage grouse nest site selection reported that >90% of nests were found under sagebrush (Patterson 1952: 114, Gill 1965, Wallestad and Pyrah 1974, Braun et al. 1977, Gates 1983). Other species of shrubs commonly grow in sagebrush habitats (Tisdale and Hironaka 1981) but are seldom used by nesting sage grouse. Only Hulet et al. (1984) reported a relatively high incidence (34%) of sage grouse use of shrubs other than sagebrush (hereafter called nest shrub species) for nest sites. Unfortunately, Hulet et al. (1984) did not address the relationship of nest shrub species to habitat quality and nesting success. Our purpose is to describe the use of nest shrub species by sage grouse in southeastern Idaho and to test the hypothesis that nesting success for grouse nesting under sagebrush is greater than that of grouse nesting under other plant species. We thank E. F. Cassirer, J. F. Kennedy, R. R. Spahr, C. M. Stinson, and D. W. Stinson for aid in collecting nest data. We also acknowledge the support of the Bureau of Land Management, U.S. Forest Service, and Idaho Department of Fish and Game. This manuscript was improved by reviews provided by J. J. Beecham, C. E. Braun, J. A. Crawford, R. L. Eng, T. P. Hemker, J. W. Hupp, T. E. Remington, and an anonymous referee. This paper is a contribution from Idaho Federal Aid in Wildlife Restoration Project W-160-R and contribution No. 560 of the Idaho Forest, Wildlife, and Range Experiment Station.

Effects of Predation and Hunting on Adult Sage Grouse Centrocercus urophasianus in Idaho

Although sage grouse Centrocercus urophasianus have declined throughout their range in North America, little is known about annual mortality patterns of this species. Thus, we summarize a long-term data set on timing and causes of mortality of sage grouse. Predation was the most common cause of death for radio-marked sage grouse. For adult males, 83% of deaths were attributed to predation and 15% to hunting. However, for adult females, 52% of deaths were caused by predation while 42% were attributed to hunting. We rejected the hypothesis that type of mortality (predation vs hunting) was independent of gender of sage grouse. For males, 70% of deaths occurred during spring and summer (March-August) and 28% occurred in September-October. For females, 52% of mortalities occurred during spring and summer and 46% occurred in September-October. We rejected the hypothesis that time of death is independent of the gender of sage grouse. In six of 15 years (40%), harvest rates for adult females may have exceeded 10% while this rate was only exceeded in two of 15 years (13%) for adult males.

Renesting by sage grouse in Southeastern Idaho

Renesting in Tetraonidae has been investigated in a number of studies (e.g., Patterson 1952, Zwickel and Lance 1965, Giesen and Braun 1979, Parker 1981, Bergerud 1988, Bergerud and Gratson 1988). Unfortunately, information on renesting by Sage Grouse (Centrocercus urophasianus) is limited and highly variable. Both Patterson (1952:105) and Eng (1963) reported that renesting by Sage Grouse is relatively rare (<10%). However, Bergerud (1988) suggested that renesting rates by this species exceed 40%, based on a synthesis of the literature and Petersens (1980) report that 7 of 17 (41%) radio-marked Sage Grouse renested. The relative vulnerability of nests and life expectancy of the female may strongly influence renesting rates in grouse (Bergerud and Gratson 1988). Bergerud and Gratson (1988) argued that if predators are active near a Sage Grouse nest, the probability of nest loss is high because of relatively sparse cover. Thus, nest abandonment and renesting would be an advantageous strategy for this species. However, grouse with long life expectancies should renest less often than shorter lived species (Bergerud and Gratson 1988) and yearlings should renest less often than adults (Bergerud 1988). Sage Grouse have relatively long lives (Patterson 1952, Bergerud 1988) which, therefore, should result in lower renesting rates than other grouse species. The objectives of this study are to document renesting rates by Sage Grouse in Idaho and to test the hypotheses that yearling and adult Sage Grouse nest and renest at the same rates.

POPULATION GENETICS OF GUNNISON SAGE-GROUSE: IMPLICATIONS FOR MANAGEMENT

Abstract The newly described Gunnison sage-grouse (Centrocercus minimus) is a species of concern for management because of marked declines in distribution and abundance due to the loss and fragmentation of sagebrush habitat. This has caused remaining populations to be unusually small and isolated. We utilized mitochondrial DNA sequence data and data from 8 nuclear microsatellites to assess the extent of population subdivision among Gunnison sage-grouse populations in southwestern Colorado and southeastern Utah, USA. We found a high degree of population structure and low amounts of gene flow among all pairs of populations except the geographically adjacent Gunnison and Curecanti populations. Population structure for Gunnison sage-grouse was significantly higher than has been reported for greater sage-grouse (C. urophasianus). Further, we documented low levels of genetic diversity in some populations (particularly Dove Creek/Monticello and Piñon Mesa with an average of only 3.00 and 2.13 alleles per locus respectively) indicating that translocations from larger, more genetically diverse populations may be warranted. Bayesian analysis identified 3 potential migrants (involving San Miguel, Dove Creek/Monticello, Crawford, and Curecanti). Further, this analysis showed that 4 individuals from Cerro/Cimarron were more closely related to birds from San Miguel than to its geographically closer neighbors Gunnison and Curecanti. This suggests the Cerro/Cimarron area may act as a stepping stone for gene flow between San Miguel and Gunnison and that habitat restoration and protection in areas between these 2 basins should be a priority in an attempt to facilitate natural movement among these populations. Conservation plans should include monitoring and maintaining genetic diversity, preventing future habitat loss and fragmentation, enhancing existing habitat, and restoring converted sagebrush communities.

Population estimation techniques for lekking species.

Abstract With the decline of many lekking species, the need to develop a rigorous population estimation technique is critical for successful conservation and management. We employed mark–resight methods to estimate population size for 2 lekking species: greater sage-grouse (Centrocercus urophasianus) and Gunnison sage-grouse (Centrocercus minimus). We evaluated 2 different estimators: Bowdens estimator and the mixed logit-normal mark–resight model. We captured and marked 75 greater sage-grouse. We counted marked and unmarked birds as they attended 15 known leks. We used 36 and 37 marked Gunnison sage-grouse to estimate population size in 2003 and 2004, respectively. We observed marked and unmarked Gunnison sage-grouse daily as they attended 6 leks in 2003 and 3 leks in 2004. Based on our examination of the assumptions of each mark–resight estimator, relative to behavior and biology of these species, we concluded the mixed logit-normal mark–resight model is preferred. We recommend wildlife managers employ mark–resight approaches when statistically rigorous population estimates are required for management and conservation of lekking species.