Migration, Hibernation, and Movement Ecology
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 to 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
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
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.
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