Effects of Land Use and Management
Abundance and Annual Fecundity of Burrowing Owls in the Coachella Valley
Western burrowing owl (Athene cunicularia hypugaea) populations have declined in most areas of California over the past several decades. Burrowing owls were considered extirpated from the Coachella Valley region of southern California in the early 1990s but recent surveys found a significant burrowing owl population in Coachella Valley. The Coachella Valley Multiple Species Habitat Conservation Plan (CVMSHCP) is implemented by the Coachella Valley Conservation Commission (CVCC) and includes objectives for burrowing owl monitoring and research in the Coachella Valley. In August 2025, we began work in the region to support the CVCC’s efforts to provide a long-term conservation strategy for burrowing owls in the CVMSHCP. Our objectives in 2025 were to: 1) revisit survey detections of owls and burrows to determine the proportion that were still occupied during the non-breeding season; and 2) capture and color band as many adult and juvenile owls as possible to allow for individual identification and future documentation of owl movements. In 2025, we banded 141 burrowing owls and revisited 318 burrows where burrowing owls were detected during the breeding season. In 2026, we plan to expand our surveys throughout Coachella Valley, monitor nests to document breeding productivity, and deploy satellite transmitters to document seasonal movements and migration behavior of owls in the Coachella Valley. Monitoring results will help the CVCC develop management strategies that promote the long-term persistence of the Coachella Valley burrowing owl population.
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
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
The Consequences of Rattlesnake Mitigation Translocation
Translocation is often perceived as a humane mitigation strategy that addresses human-wildlife conflict while maximizing positive outcomes for wildlife. Yet, the outcomes of long-distance translocation are highly variable and often poorly understood, particularly in reptiles. Of the thousands of rattlesnakes translocated each year in the U.S., only a handful are followed post-release to document fate, behavior, or movements. In 2024 and 2025, we surgically implanted VHF transmitters in 34 adult prairie rattlesnakes in a state park near Lander, Wyoming and we tracked their movement, survival, and behavior throughout the active season. We compared movement, behavior, and survival between translocated snakes and control (non-translocated) snakes. These data will be used to 1) assess the outcomes of long-distance translocation in this population and 2) test predictions generated from six hypotheses that explain post-release mortality in rattlesnakes.
Emily Martin