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Causes of Species Declines
Cumulative Effects of Agriculture and Drought on Migratory Shorebird Refueling in the Prairie Pothole Region
Millions of shorebirds in North America use agricultural areas in the Prairie Pothole Region of the northern Great Plains to refuel during migratory stopovers. However, increased neonicotinoid insecticide use and wetland loss from agricultural practices and may threaten their ability to efficiently refuel and migrate. This project quantifies agricultural and drought impacts on migratory shorebirds and their prey in North and South Dakota of the Prairie Pothole Region. Objectives include 1) quantifying neonicotinoid exposure and accumulation, and 2) investigating how neonicotinoids, agricultural practices, and drought directly and indirectly influence shorebird body condition and invertebrate biomass. Over two spring and two fall migration seasons in 2021-2023, we measured neonicotinoid concentrations in water (n = 96) and shorebird plasma (n = 174) samples to document exposure and accumulation. In 2023, we quantified pesticide concentrations from > 200 additional compounds in invertebrates (n = 67). We evaluated shorebird body condition, invertebrate biomass, habitat characteristics, and the percentage of surrounding cropland cover around each wetland to inform habitat quality. Neonicotinoid detections fluctuated across seasons in water (7-47%) and in shorebird plasma samples (20-60%). Pesticide detections in invertebrates were higher in fall 2023 (48%) compared to spring 2023 (42%). A few plasma concentrations reached levels that are thought to cause physiological problems. Shorebirds with neonicotinoid detections in their plasma had lower fattening indices (measured by plasma metabolites). Pesticide detections in water or invertebrates did not affect shorebird body condition or prey availability. Surrounding cropland cover around wetlands reduced invertebrate biomass, shorebird fattening indices, and shorebird uric acid levels. During drought conditions, shorebirds had lower fat levels and fewer neonicotinoid detections in their plasma. Our results allow managers to propose changes in management practices (e.g., flooding fields, maintaining vegetation buffers) and farming policies that would benefit refueling of migratory shorebirds.
Shelby McCahon
Monitoring and Measuring Wild Animals Without the Need for Capture
Rodents are reservoirs for zoonotic diseases and provide a model system for virology and immunology research. Studying wild rodent populations typically involves live-trapping. Capturing and handling rodents is time intensive, may expose handlers to zoonotic diseases, and occasionally results in trap-related animal mortality. The drawbacks of live-trapping methods commonly used for rodents are especially important to consider when working with rare species. The northern Idaho ground squirrel (Urocitellus brunneus) is a threatened species endemic to just two counties in west-central Idaho. We are working with a team of engineers, computer scientists, mathematicians, and AI experts to develop a prototype device, WildMarker, explicitly designed to passively document species diversity, abundance, and body size and morphological data without the need for capture and handling. We have completed a prototype design and we will deploy 10 WildMarker boxes in the field in summer 2026 to compare and validate results with traditional trapping methods (baited Tomahawk traps checked regularly by field biologists). An image-recognition A.I. will enable real-time species identification in future iterations of WildMarker. This project will utilize the previously marked populations of northern Idaho ground squirrels, Columbian ground squirrels, and chipmunks from our prior research at study sites in central Idaho. The western deer mouse (Peromyscus sonoriensis) will serve as a fourth, nocturnal study species to evaluate WildMarker performance in low light conditions.
Effect of Selenium Accumulation on Yuma Ridgway’s Rails at the Salton Sea, California
Emergent marshes around the Salton Sea in southeastern California support one of the largest populations of the federally endangered Yuma Ridgway’s rail. Much of the rail habitat in the region is managed by state and federal agencies, but marshes have appeared recently at agricultural drainage outlets around the Salton Sea. These 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 lower concentrations of selenium. Elevated selenium causes embryo malformations, and, hence, these ag-fed 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 ag-fed marshes pose risks to Yuma Ridgway’s rails. During 2020-2025, we captured 266 rails in 12 marshes around the Salton Sea. We attached GPS transmitters to 134 adult rails and located 89 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 agency managed marshes, whereas selenium concentration in rail feathers did not differ between the two marsh types. We collected 93 eggshell samples and 27 whole eggs from 60 of the 89 nests across the 6 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. We also captured 27 rails, deployed 19 transmitters, and collected 3 eggshell samples from 3 nests in marshes along the lower Colorado River. Selenium concentration of rail prey was higher in ag-fed marshes compared to those managed by state and federal agencies.
Cydney Yost
Comparison of Spatial and Temporal Migration Rates in Yuma Ridgway’s Rails
Understanding variability in spatial and temporal movement patterns within a species is critical for implementing effective conservation strategies. This is especially true for endangered species like the Yuma Ridgway’s rail (Rallus obsoletus yumanensis) – a species dependent on fragmented and dissipating wetland habitat in the U.S. The Lower Colorado River and the Salton Sea both provide critical habitat for Yuma Ridgway’s rails. Between 2016 and 2025, we tagged rails with solar GPS transmitters during the breeding season at the Salton Sea and along the Lower Colorado River in California, Arizona, Nevada, and Northern Mexico. We used the GPS data to quantify and compare the home range sizes, seasonal dispersals, and migrations. The propensity to migrate differed, with rails from the Lower Colorado River initiating migration to Mexico more frequently (~40%) than those from the Salton Sea (~4%). Furthermore, rails from the Salton Sea maintained consistent home range sizes year-round, while rails’ home ranges in other populations increased in the non-breeding season. Our results showcase a need for implementing population-specific conservation strategies. We recently presented results at the Western Section of The Wildlife Society’s annual conference. Current efforts involve examining the environmental and demographic drivers of partial migration in Yuma Ridgway’s rails. In 2026, we hope to use toenail samples to detect migration and dispersal events using stable isotope analysis.
Natalya Hebert
Post-breeding Movements, Migration Resource Selection, and Survival of Burrowing Owls
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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 nest burrows. Burrowing owls are relatively well studied during the breeding season but relatively little is known about their ecology outside of the breeding season. Our results thus far have documented that 32% of adult burrowing owls move to a distinct post-breeding home range before they migrate (post-breeding movement) where they spend approximately 2.5 months of their annual cycle. We have been working with numerous cooperators to attach solar-powered satellite transmitters to 488 burrowing owls in the U.S., Canada, and Mexico over the past 13 years which enables us document movements and resource selection of burrowing owls after they leave the breeding grounds. The transmitters also allow us to document daily survival probabilities across the owl’s annual cycle. The objectives are: 1) thoroughly describe post-breeding movements of migrating burrowing owls, 2) investigate why some burrowing owls make a post-breeding movement prior to migration while others do not, 3) document habitat selection of en-route migrating burrowing owls, and 4) identify factors that influence survival. The results of this project will help ensure that management efforts that target burrowing owls do not neglect to consider post-breeding and migration life stages.
Anthony Locatelli
Ecological Pressures Governing Hibernation Habitat Selection in Northern Idaho Ground Squirrels
Northern Idaho ground squirrel populations declined in the 20th century such that the species now occupies <1% of its historic range. Current management actions focus on creating open-canopy active-season habitat for squirrels. However, many northern Idaho ground squirrels move away from active-season ranges to hibernate, often selecting hibernaculum sites in forests. It is important for managers to incorporate hibernation habitat needs into forest management plans, but the underlying ecological pressures driving hibernation site selection have been poorly understood. Competition with the sympatric Columbian ground squirrel, predation avoidance, selection for an optimal thermal environment, and spring flood avoidance are among the hypotheses we tested to explain variation in squirrel hibernation site selection. To test these alternative hypotheses, we attached radio-collars to squirrels to document hibernation habitat selection, deployed trail cameras to document badger predation of hibernating squirrels, and trapped Columbian ground squirrels to estimate population size and habitat use. We found that: (1) northern Idaho ground squirrels actively avoided hibernating in seasonally flood-prone areas, (2) Columbian ground squirrels influenced how far northern Idaho ground squirrels moved to hibernate and in what kind of habitat they hibernated, and (3) Columbian ground squirrels significantly increased badger predation risk for hibernating northern Idaho ground squirrels but northern Idaho ground squirrels reduced badger excavation risk by hibernating close to trees. Our results demonstrate that well-drained soils and trees a key habitat features for hibernating northern Idaho ground squirrels and document that Columbian ground squirrels reduce survival of a threatened species via apparent competition. Alice Morris completed her MS Thesis in 2025 and we are currently completing manuscripts for submission to journals.
Alice Morris
Habitat Selection and Competition Between Sympatric Ground Squirrels
​The northern Idaho ground squirrel is a federally threatened species endemic to west-central Idaho. The Columbian ground squirrel occupies a larger range across the Pacific Northwest and overlaps that of the northern Idaho ground squirrel. Habitat loss is the leading hypothesis to explain population declines for the northern Idaho ground squirrel, and hence habitat restoration is considered a potential tool for species recovery. However, the species recovery plan also calls for site-specific management of Columbian ground squirrels. We must understand how these two sympatric species partition space on a micro-habitat scale for future restoration efforts to help restore populations. We will utilize 12 years of capture locations and vegetation measurements from a long-term habitat restoration experiment – along with abiotic habitat metrics and population densities – to quantify the spatial distribution and habitat dynamics of both species. We will also attach transmitters with geolocators to northern Idaho ground squirrels and Columbian grounds squirrels to compare hibernacula site selection and hibernation behavior across an elevational gradient. This project aims to distinguish between the micro-habitat requirements of these species and inform future management efforts aimed at recovery and de-listing of the threatened northern Idaho ground squirrel.
Emma Hakanson