Progress 07/01/03 to 09/30/06
Outputs
To characterize demographic processes in Greater Sage-grouse (Centrocercus urophasianus), we monitored 12 lek sites in a 3800 km2 area in Eureka County, Nevada. The long-term goal of this ten-year study is to assess the impact of Sierra Pacific Power Company's Falcon-Gondor transmission line on sage grouse demography and population dynamics. We used mark-recapture, lek observations, nest & brood monitoring, vegetation sampling, and radio telemetry to estimate key demographic parameters. A total of 679 sage grouse (532 male, 138 female, & 9 unknown sex young of the year) have been banded with both a color and metal band during the first three years of the study. We used lek observations, recaptures, and resighting of banded individuals to estimate demographic parameters and movement probability. We used a robust design structure to analyze capture-recapture data for males (making use of the pattern of captures among months of the lekking period) which allowed us to
estimate size of the male population, annual survival of males and the probability that the average male attended a lek at least once during the spring. We used radio telemetry to locate nesting females, follow broods through fledging, and to estimate female survival. Once located, nests were monitored to estimate nest success, and nest site vegetation was measured after hatch. Nest site vegetation characteristics were evaluated as covariates in a nest success analysis in Program MARK. Our data suggested that nests with 65% total shrub cover have twice the probability of success than nests with 25% (0.29 versus 0.15 respectively). Hens with broods were checked once a week and their young counted until young were independent (45-50 days). We have tagged 184 chicks with Passive Integrated Transponder tags for permanent identification in the last two years of the study. We estimated chick survival for the first 50 days at 0.2329 (95% CI = 0.2059-0.2599) using the Kaplan Meier method of
survival estimation. Program MARK known fate data type was used to estimate an annual female survival of 0.5589 (95% CI = 0.4876-0.6303). Our estimates for size of the regional male population ranged from 381 (SE = 37, 2004) to 472 (SE = 44, 2006). We estimated annual survival of males = 0.63 (SE = 0.04). Probability of being present on a lek during the breeding season also did not vary among years or among age classes, although there was modest evidence (sum of model weights for models containing an age effect for probability of presence = 0.4) that juvenile males (ca. 10 months old) were less likely to be present (presence probability = 0.91, SE = 0.14) during the entire breeding season than was true for adult males (presence probability > 0.99, SE < 0.01).
Impacts
This project will enhance our understanding of factors regulating sage grouse in Nevada, where few studies have been conducted. This species is being considered for listing under the Endangered Species Act, which will have substantial implications for much of rural Nevada.
Publications
- Sedinger, J. S., M. Atamian, C. Frey, and B. Comstock. 2007. ROBUST DESIGN ESTIMATES OF POPULATION SIZE AND DEMOGRAPHIC PARAMETERS FOR MALE SAGE GROUSE IN CENTRAL NEVADA. Proceedings Euring 2007, Dunedin, NZ. (Abstract).
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Progress 01/01/05 to 12/31/05
Outputs
We have banded 474 sage grouse (378 males, 88 females, and 8 unknown) in the first three years of the project. During spring trapping we captured 161 new birds in 2003, 120 in 2004, and 127 in 2005. In addition to new captures, we recaptured 27 and 46 unique individuals in 2004 and 2005, respectively. During summer 2005, we captured 66 new sage grouse, 22 males, 36 females (26 of which were radio collared), and 8 unknown. Including multiple captures of the same individual within the same year we have captured a total of 602 sage grouse over the first three years of this study. We estimated that adult males survived each of the first two years with a probability of 0.68, while annual survival for juveniles was 0.67. Probability of attending a lek at some time during the spring equaled 1.0 for both age classes of males. We detected individual adult males at some point during the lekking period with a probability equal 0.41 and 0.49 during the first two years of the
study, respectively. Overall encounter probabilities for juvenile males were 0.37 and 0.55. We estimated the size of the male population in the study area equaled 683. The best models of annual survival for females constrained survival during the months of March through August to be the same and survival during September and October to be the same, but different from spring-summer. Monthly survival estimates from the best model ranged from a high of 0.9782 in the spring and summer months to a low of 0.8938 in September and October. Using estimates from a model in which daily nest survival was held constant relative to all variables, including nest age, we estimated daily survival rate equaled 0.9562, producing an estimate of nest success equal to 0.29 for incubation only (28days), or 0.18 for the total nest exposure period (38days). We also conclude that nest site vegetation may be having an effect on nest success, but the direction and the magnitude of the effect is unknown. With
increased sample size in future years we should be able to clarify the effects of nest vegetation on nest success.
Impacts
This project will enhance our understanding of factors regulating sage grouse in Nevada, where few studies have been conducted. This species is being considered for listing under the Endangered Species Act, which will have substantial implications for much of rural Nevada.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Banding Results: We banded 279 sage grouse (251 males and 28 females) during the first two field seasons. 14 new females and 106 new males were banded in 2004. Of those birds banded, 58 unique individuals were recaptured during subsequent banding attempts or were re-sighted during observation periods in 2004.We counted (sum of maximum number observed per lek) 233 males and 56 females in 2003 and 265 males and 74 females in 2004 for all leks. Attendance numbers show an early season peak in late March followed by a decline during late May to early June that was variable between years. Total counts on leks tend to underestimate the number of sage grouse in the study population because of turnover of adults and juveniles throughout the season. Using our recapture data and banding totals we performed a Bowdens estimation (Bowden 1993) from program NOREMARK (White 1996) and calculated a preliminary estimate of 342 male grouse (95% confidence interval (CI) of 256-422) for
the active leks used in the study. As of October 2004 5 banded males and 4 radio collared females have been reported as harvested during hunting season (1 female in 2003, 3 in 2004). Mortality from hunting and number of bands returned will be obtained from NDOW and BLM to increase the precision of our estimates of grouse life history traits.Radio marked birds were located approximately every third day. Over both years of the study we have 353 GPS locations during breeding, brood rearing and over winter. We estimated daily nest survival for both years at .9605(CI .9308-.9750) using the data collected (Table 4). The daily nest survival estimate was raised to the 28th (average days of incubation) power to obtain an estimate of nest success of .3235(CI .1670-.4923) for both years. We also raised daily nest survival estimate to the 38th (average days of incubation plus exposure during laying period) power to obtain an estimate of nest success of .2162(CI .0881-.3822)
Impacts
This project will enhance our understanding of factors regulating sage grouse in Nevada, where few studies have been conducted. This species is being considered for listing under the Endangered Species Act, which will have substantial implications for much of rural Nevada.
Publications
- Comstock, B. C., and J. S. Sedinger. 2004. Sage-grouse population dynamics and movement in central Nevada. Twenty-fourth meeting of western agencies Sage Grouse and Columbian sharp-tailed Grouse Technical Committee. Wenatchee, WA.(Abstract)
- Comstock, B. C., and J. S. Sedinger. 2004. Sage-grouse population dynamics and movement in central Nevada. The Wildlife Society 2004 Annual Conference, Calgary, AB, Canada.(Abstract)
- Comstock, B. C., and J. S. Sedinger. 2004. Dynamics of Sage Grouse (Centrocercus urophasianus) Populations in Response to Transmission Lines in Central Nevada. Progress Report to Nevada Departmentof Wildlife and BLM.
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Progress 01/01/03 to 12/31/03
Outputs
Our goal in this project is to assess the relationship between demography of sage grouse, which determines population dynamics, and environmental variables. Environmental variables we are measuring include vegetation near nests, predator abundance and distance from a transmission line. We are using marking and observation of individual grouse to estimate survival, clutch size, nest success, recruitment and movement of grouse. We completed our first field season in 2003. We established a remote field camp, found study leks and intiated amrking of sage grouse. Fifteen females and seven males were fitted with Advanced Telemetry Systems. Nests of radio-collared birds were located by triangulation and monitored twice weekly from April to June. On average, most nests were located within four miles of the breeding lek (Wakkinen et al 1992), and we concentrated our effort within a four-mile radius of active leks. Nest locations were recorded using a GPS and nest success and
nesting habitat were recorded for all nests discovered. Nest site habitat type and shrub size were recorded as nest success can be related to vegetation at the nest site (Connelly et al 1991). Once discovered, brood-rearing areas were monitored regularly until fledging for the presence of radio marked females and their broods. After nesting, all radio-collared birds were triangulated twice each week. We sampled nest vegetation for each radio-collared female that initiated a nest. We collected plant height and plant species type for plots (Sveum et al 1998) around a nest as well as control plots randomly chosen throughout the study area. For each plot we evaluated the vegetation in a 1 m2 circle around the nest as well as 5, 20X50 cm plots along each of two perpendicular 10 meter transects centered at the nest. We banded 160 sage grouse (145 males and 15 females) during the first field season. Of those birds, 21 were recaptured during subsequent banding attempts and 9 bands were
re-sighted during observation periods. Using our recapture data we performed a Bowden estimation (Bowden 1993) from program NOREMARK (White 1996) and calculated a preliminary estimate of 490 male grouse (95% confidence interval (CI) of 247-993) for the active leks used in the study. These estimates will improve when more birds are captured, recovered and re-sighted in the future. During our observations we counted, using maximum number observed per lek on a single day, 233 males and 56 females for all leks. As of October 2003 two banded males and 1 radio collared female have been reported as harvested during hunting season. Mortality from hunting and number of bands returned will be obtained from NDOW and BLM to increase the precision of our estimates of grouse life history traits.
Impacts
This project will enhance our understanding of factors regulating sage grouse in Nevada, where few studies have been conducted. This species is being considered for listing under the Endangered Species Act, which will have substantial implications for much of rural Nevada.
Publications
- None yet. Progress Report for BLM, NDOW and Sierra Pacific 2003.
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