Effects of Land Use and Management
Grouse & Grazing: effects of cattle grazing on greater sage-grouse
Despite many studies of greater sage-grouse (Centrocercus urophasianus) habitat requirements, we know surprisingly little about the effects of livestock grazing on sage-grouse populations. As a result, various groups make claims about the presumed effects of livestock grazing on sage-grouse, and litigation over this issue is common. We brought together a multi-partner team to develop and implement a 10-year study with replicated experimental grazing treatments to evaluate the effects of grazing on demographic traits and habitat characteristics of sage-grouse. The results will help guide management actions (and inform policy and litigation decisions) throughout southern Idaho and throughout the species’ range. In 2023, we completed our 10th and final year of data collection for the study. Over the course of the project, we attached transmitters to 1,343 sage-grouse hens and located and monitored 1,216 nests of those radio-marked hens. We have also measured vegetation characteristics at those nests and 3,196 random plots within 21 grazing treatment pastures. In addition, we have also collected 12,446 insect pitfall samples, 6,334 insect sweep net samples, and measured grazing intensity within those same 21 treatment pastures.
Monitoring and Management of Burrowing Owls at
Naval Air Station Lemoore
Western burrowing owls (Athene cunicularia hypugaea) are declining or have disappeared from many portions of their historic breeding range. The decline of burrowing owl populations is often attributed to conversion of native grasslands to agriculture and urban development, and to declines in abundance of burrowing mammals that the owls rely on for creation of nest burrows. One place where urban development and burrowing owl habitat intersect is Naval Air Station (NAS) Lemoore. We plan to thoroughly monitor burrowing owls on NAS Lemoore with the objectives of: 1) documenting burrowing owl return rates, 2) quantifying reproductive success, 3) examining the effects of human disturbance on return rate and reproductive success, 4) providing managers with data and information that will ensure minimal conflicts between owls and base operations, and 5) when development in burrowing owl habitat is critical to the Department of Defense mission, examining the efficacy of mitigation strategies. The results of this research will provide insight into the status of the NAS Lemoore burrowing owl population and how to mitigate the effects of development when development is unavoidable.
Effectiveness of habitat restoration as a recovery tool for northern Idaho ground squirrels
The northern Idaho ground squirrel is a federally threatened species endemic to west-central Idaho. Squirrel populations are fragmented such that the species currently occupies <1% of its historic range. Habitat loss resulting from anthropogenic fire suppression is the leading hypothesis to explain past population declines and fragmentation. We are using a before-after-control-impact design to experimentally evaluate the effectiveness of habitat restoration treatments – forest thinning and prescribed burning adjacent to patches occupied by squirrels and prescribed burning within patches occupied by squirrels – as potential tools to recover the species. This project was initiated in 2014 and assessment of experimental restoration treatments are ongoing. Over the past 10 years, we have marked 2087 individual squirrels for survival analyses and attached 349 radio-collars and 263 geolocators to squirrels to document foraging, habitat selection, and hibernation behavior at 13 study sites. We also collected ~1900 fecal pellet samples from captured squirrels for diet analysis and collected detailed vegetation structure and composition data to assess forage availability and habitat quality. Amanda Goldberg completed her dissertation in 2018, Austin Allison completed his thesis in 2022, and Alice Morris began her thesis work in 2021. To date, we have published 14 papers in peer-reviewed journals from this project.
Effects of Livestock Grazing and Habitat on Predator-Specific Nest Mortality and Spatiotemporal Activity Patterns of Sage-Grouse Nest Predators
Nests of greater sage-grouse (Centrocercus urophasianus) are depredated by a suite of nest predators that vary in functional traits (e.g., hunting mode). Thus, identifying the mechanisms that influence nest failure can be challenging without identifying the explicit predator species responsible for nest depredation events. We developed a molecular method for identifying sage-grouse nest predators using DNA collected from depredated nests and evaluated how cattle grazing and habitat influences predator-specific nest mortality. To validate our molecular method, we deployed artificial nests with trail cameras and compared molecular results to camera footage. We monitored sage-grouse nests at 5 study sites in Idaho within pastures that varied in grazing intensity and collected DNA samples from 114 depredated nests. Lastly, we deployed camera traps across 6 pastures to quantify how the presence of cattle influences the spatiotemporal activity patterns of coyotes (Canis latrans). We detected nest predators via DNA left on eggshells at 67% of the depredated sage-grouse nests. Grazing did not influence the probability of nest predation by either coyotes or corvids. Sagebrush canopy cover was negatively associated with the probability a coyote depredated a nest, the distance to water was positively associated with the probability a corvid depredated a nest, and ambient temperature was negatively associated with the probability that either a coyote or a corvid depredated a nest. Coyote presence within a pasture was positively associated with the presence of cattle, and coyotes did not shift their diel activity patterns in response to cattle. Our study suggests that domestic cattle grazing does not influence predator-specific nest mortality, at least not for corvids or coyotes. Further, our study suggests that coyotes do not partition themselves in space or time to avoid cattle.
Nolan Helmstetter
Effects of aircraft noise on greater sage-grouse in southern Idaho
In southern Idaho, the U.S. Air Force conducts aviation military training and combat simulations. These combat simulations involve jet planes flying at low altitude and high speeds focused around two bombing ranges and a collection of emitter stations in Owyhee County. These installations and flyovers occur through greater sage-grouse habitat. Since 1965, greater sage-grouse have experienced a range-wide population decline and are impacted by other types of noise disturbance and human infrastructure. The military has restricted use of some emitters to minimize impacts on sage-grouse attending leks, but we lack information on the effectiveness of these restrictions, or the impacts of intermittent noise on greater sage-grouse. In addition, low-altitude flyovers occur outside of these restrictions, and their impacts on sage-grouse lekking and nesting behavior are still unknown. The primary objective of this project is to document the effects of intermittent noise disturbance from low-level military overflight on nest survival, lek attendance, and behavior of greater sage-grouse. We placed audio recorders and cameras at sage-grouse nests and leks to document sound levels, nest survival, lek attendance, and behavioral responses by lekking sage-grouse. From 2022-2023, we attached radio collars to 53 sage-grouse hens and monitored 26 nests, recording 7,200 hours of audio. We monitored 18 leks from 2022-2023 and collected 13,247 hours of audio and 22,413 scan-sampled behavioral observations. Our results will provide insight into the effectiveness of existing restrictions on military flights near sage-grouse leks and the impacts of intermittent anthropogenic noise disturbance on greater sage-grouse.
Reese Wray
Effects of Insecticides and Agricultural Practices on Migratory Shorebirds in the Prairie Pothole Region
Many shorebirds in North America use agricultural areas in the Prairie Pothole Region of the northern Great Plains to refuel during critical migratory stopovers, but rapid increases in neonicotinoid insecticide use in agricultural fields may pose risks to their ability to efficiently refuel and migrate. Neonicotinoids can suppress appetite, lower refueling rates, and cause rapid mass and fat loss. Additionally, neonicotinoids may reduce invertebrate populations, further diminishing the quality of agricultural wetlands for shorebirds. This project quantifies agricultural impacts on abundance, body condition, and prey biomass for migratory shorebirds in the Prairie Pothole Region. Goals of the project are: 1) to quantify the effects of neonicotinoid insecticides on shorebird physiology and invertebrate biomass, and 2) to assess habitat use and quality of agricultural wetlands used by migratory shorebirds. Across two spring and two fall migration seasons in 2021-2023, we collected plasma samples from shorebirds (n = 182; 11 species) and water samples from wetlands (n = 84) to better understand neonicotinoid exposure. We also conducted wetland (n = 84), macroinvertebrate (n = 48), and road transect surveys (n > 100) to better inform wetland quality and shorebird use. Our research provides a foundation for understanding how insecticides and agricultural practices impact shorebird physiology, wetland use, and prey biomass. Our findings will provide managers with results to potentially invoke changes in management practices (e.g., flooding fields) and farming policies.
Shelby McCahon
Effect of Selenium Accumulation on Yuma Ridgway’s Rails at the Salton Sea, California
Cydney Yost
Emergent marshes around the Salton Sea, California support one of the largest populations of the federally endangered Yuma Ridgway’s rails in the United States. Much of the rail habitat in the region is managed by state and federal agencies, but non-planned marshes have appeared recently at agricultural drainage outlets around the Salton Sea. These unplanned marshes originate from agricultural drainage water with varying concentrations of selenium, whereas the marshes managed by state and federal agencies receive Colorado River water with relatively low concentrations of selenium. Elevated selenium causes embryo malformations, and, hence, these unplanned marshes may be ecological traps for these endangered rails. We documented selenium burdens in breeding rails and selenium concentrations in rail prey items within marshes fed by different water sources to assess whether high selenium in unplanned marshes pose risks to Yuma Ridgway’s rails. During 2020-2023, we captured 218 rails in 12 marshes around the Salton Sea. We attached GPS transmitters to 96 adult rails and located 78 nests. We collected blood, feathers, egg samples from nests, and samples of common rail prey species. Selenium concentration in rail blood was higher in unplanned marshes than in state/federal managed marshes, whereas selenium concentration in rail feathers did not differ between the two marsh types. We collected 71 eggshell samples and 12 whole eggs from 56 of the 78 nests across the 4 years. We collected 713 rail prey samples (i.e., crayfish, mosquitofish) from 181 rail home ranges, 205 irrigation inflows and outflows, and 81 other sampling locations in 12 marshes. Selenium concentration of rail prey was higher in unplanned marshes compared to those managed by state/federal agencies.
Nesting success and recruitment of western grebes in Idaho
We compiled data summarizing the status of current and historical grebe populations on 770 breeding lakes across North America. The largest concentrations of adult grebes (>1000) during the breeding season were concentrated in only 5% of the breeding lakes used by grebes and most (73%) of the 770 breeding lakes supported only small numbers of breeding adults (<100). We developed this breeding lake inventory into an interactive website in partnership with the Center for Digital inquiry and Learning (CDIL) at the University of Idaho and that website will launch in early 2024. Cascade Reservoir supports the largest grebe breeding colony in Idaho. At Cascade Reservoir, we used drones to document the cause of early nest abandonment that we had observed in 2020 and 2021. We reconstructed nest histories and estimated nest fate for >3800 nests based on repeated flights and drone imagery. We estimated nest survival and examined the effects of environmental variables on nest fate. Our results indicate that daily peak wind direction, daily peak wind speed, daily precipitation, daily water level, and date influence nest fate. Daily nest survival decreased as the nesting season progressed and was also low on days when precipitation combined with winds blew into the colony. Our interactive website and research on the factors that affect nest survival will help managers implement actions that can potentially increase grebe recruitment in Idaho and elsewhere. Anne Yen defended her thesis in Dec 2023 and is graduating Spring 2024.
Anne Yen
Seasonal movements, population connectivity, and survival of
light-footed Ridgway’s Rails
Federally endangered light-footed Ridgway’s rails (Rallus obsoletus levipes) inhabit coastal wetlands within a restricted geographic range that spans the U.S.-Mexico border. These rare birds persist in a heavily urbanized landscape where an estimated 70% of historic wetlands have been lost. The wetlands that remain are fragmented and threatened by continued habitat degradation. Despite their rarity, very little is known about their seasonal movements and connectivity among occupied marshes. Moreover, captive bred light-footed Ridgway’s rails are released annually as part of species recovery efforts, but the effectiveness of the captive-breeding program to augment the population and the post-release survival and movement of captive-bred rails are poorly understood. We are developing a range-wide monitoring protocol to better estimate rail abundance and track population trends. We also are attaching satellite transmitters to captive-bred and wild-caught rails to compare survival and movement ecology between wild and captive-bred rails. Our research will improve our understanding of light-footed Ridgway’s rail demography and enhance the efficacy of current recovery efforts.
Kim Sawyer