Results of the 2022 Field Season
In February and March of 2022, we collared 137 female sage grouse across four sites, as we did not conduct field work at the Jim Sage study site in 2022. In addition, 63 hens that had been captured the two previous years were still alive and had active radio-transmitter collars.
We found 176 nests across all four sites in 2022, including 26 nests of hens that were not being actively tracked. Of the 150 nests we monitored, 113 were initial nest attempts, 33 were second nest attempts, and 4 were even third attempts, which has only been documented once in the previous 8 years of the project.
Nest Success and Chick Survival
Apparent nest success was relatively low in 2022 (24%) as compared to previous years of the project. The percentage of nests where chicks hatched successfully ranged from 20% at Pahsimeroi to 30% at Brown’s Bench and Big Butte.
After clutches hatched, we monitored the broods of 42 sage grouse hens. Brood survival to 42 days of age ranged from a high of 53% at Sheep Creek to a low of 29% at Big Butte.
We documented 68 mortalities among radio-collared birds during the 2022 field season. The number of mortalities we are able to find each season increased as compared to early years of the project, likely due to adding a telemetry flight at our sites early in the year to help the crews find birds that died overwinter. Of the 68 mortalities found, 29 were overwinter mortalities.
In 2022, we took vegetation measurements at nest sites, brood locations, and random plots across the pasture to document the plant species and amount of cover in areas used by grouse compared to random areas. We also began collecting biomass measurements at these random sites in order to investigate the effects our grazing treatments have on fuel loads.
We used three methods to estimate the percent utilization across the experimental pastures: ocular method, landscape appearance, and percent height reduction.
Utilization varied spatially within individual pastures, which highlights the need for spatially explicit methods of mapping utilization. By accounting for and mapping this spatial variation, we will be able to investigate how utilization patterns may affect nest site selection of sage-grouse within our study pastures.
Certain methods of measuring utilization may be more beneficial for answering particular questions, and further investigation into the most appropriate method is warranted. It will be essential to select the most appropriate method(s) of assessing utilization in order to ascertain how changes in spring grazing affect greater sage-grouse, habitat and wildfire.
In the first two weeks after hatching, sage-grouse chicks depend on a high-protein diet. To determine what’s on the menu, we used sweep nets, pitfall traps and ant mound surveys to collect and record the species and biomass of arthropods present. These collections were completed during the 2021 field season, and currently a graduate student and multiple technicians are working on identifying the species collected.
Since the beginning of our study, we have determined the fate of 1149 sage grouse nests (423 within post-treatment experimental pastures) conducted vegetation sampling at 7,448 plots (breeding and post-breeding season surveys combined) and taken utilization measurements across all study pastures each year. With this continued effort and large sample size, we will be able to make powerful inference regarding the specific effects of spring cattle grazing on sage-grouse populations and habitat in Idaho, and these results will be relevant throughout the species’ range
For the 2023 field season, we plan to wrap up our research at the sites and begin analysis of the data soon after.