Deploying Ultralight Solar Transmitters on Rufous (Selasphorus rufus) and Ruby-throated Hummingbird (Archilochus colubris) to Document Movement Ecology

Recent innovations in wildlife tracking have advanced the field of movement ecology, yet applications to the smallest species have remained limited by the acceptable weight of tracking devices relative to that of the organism. Despite a century of banding, hummingbird migration across North American remains poorly understood, limiting efforts to develop effective conservation strategies in the U.S. Yet, recently, a new technological advancement has emerged and has demonstrated its astounding capacity (Rhodes et al. (2025). Nature Methods. in-review). Here we propose to use a novel, ultralight, solar-powered transmitter, the BlūMorpho transmitter, that enables continuous, fine-scale tracking of North American hummingbirds—on species that weigh less than 5 g. This technology will allow us to obtain migration tracks of North American hummingbirds throughout the Southeastern U.S. and even more broadly, the entirety of North America - a previously impossible feat. We propose to conduct a multi-state effort to capture and deploy transmitters on two species in the Southeastern U.S.—Rufous Hummingbird (Selasphorus rufus) and Ruby-throated Hummingbird (Archilochus colubris). The BlūMorpho transmitter combines solar power with near real-time transmission via a ubiquitous crowd-sourced network; all in a device weighing just 0.058–0.060 g. These transmitters are also compatible with the Motus Wildlife Tracking Network enabling continuous, remote tracking at high spatial and temporal resolution with no need for recovery. In total, we will deploy 600 BlūMorpho transmitters across 7 Southeastern U.S. states and will also present our work at a prestigious avian conference—the American Ornithology Conference. By leveraging our expert team, we will not only collect novel, individual tracks to describe migration and stopover, ecology for conservation efforts but will then utilize these tracks to better inform large-scale population models in an open-access format hosted by the eBird (Cornell Lab of Ornithology). Our expert team consists of leads in the field of biology and wildlife (Dr. Geoffrey Hill (PI), Auburn University), collaborative migratory bird research (Dr. Emma Rhodes (Co-PI), Kyle Shepard, Banding Coalition of the Americas), spatial analyses with avian tracking data (Hannah Wright, M.Sc., University of Georgia), multivariate population-level data (Dr. Orin Robinson, eBird/Cornell Lab of Ornithology), and technological expertise (Dr. David La Puma, Cellular Tracking Technologies). With many hummingbird species currently experiencing population declines, identifying key areas along their full-annual cycle to focus conservation efforts is critical for population management and to understand how these species interact with encroaching urbanization. We expect this work to produce millions of data points in near real-time which then will be used for population-level and ecological modeling. This project will not only benefit the Southeastern U.S. but will benefit hummingbird research and conservation on a continental scale. Our methodologies will be applicable for federal, state, and NGO replication in a scientific and conservation driven manner. Additionally, our results will help to facilitate application of these transmitters to other species which currently have little- to no- tracking data due to weight or other tracking limitations. This advancement opens a new frontier in movement ecology, enabling year-round, individual-based studies in a group previously inaccessible to telemetry.