In a cosmic dance of celestial intrigue, Earth’s magnetic field faces periodic disruptions, choreographed by solar flares and other cosmic outbursts. Picture this: a symphony of avian navigators, embarking on nocturnal journeys, their path directed by an invisible force influenced by the whims of the sun.
Enter the daring researchers from the University of Michigan and their scientific comrades, armed with massive datasets harvested from the ether using U.S. Doppler weather radar stations and ground-based magnetometers. These instruments, akin to magical wands, measure the intensity of magnetic fields, unveiling the secrets of the nocturnal bird migration ballet.
In their cosmic quest, the intrepid scientists discovered a celestial ballet hiccup — a 9%-17% dip in the number of migrating birds during severe space weather events, both in the vernal bloom of spring and the autumnal tapestry of fall. Those brave avian wanderers, choosing to soar through cosmic turmoil, appeared to face an extra layer of challenge, particularly when navigating the skies under the shroud of autumnal overcast.
The findings, akin to an ancient scroll unfurling new revelations, are poised for their debut in the mystical realm of the Proceedings of the National Academy of Sciences. The researchers, modern-day wizards of correlation, unveil the heretofore unknown relationships between the dynamics of nocturnal bird migration and the cosmic disturbances in the geomagnetic tapestry.
Lead author Eric Gulson-Castillo, a doctoral sorcerer in the U-M Department of Ecology and Evolutionary Biology, shares the mystical insight, “Our findings highlight how animal decisions are dependent on environmental conditions — including those that we as humans cannot perceive, such as geomagnetic disturbances — and that these behaviors influence population-level patterns of animal movement.”
Earth’s magnetic cloak, regularly brushed by solar outbursts, weaves tales of colorful auroras and, at times, disrupts the enchantments of satellite communications, human navigational spells, and power grid enchantments.
The NEXRAD radar, a magical oracle of the skies, detects clusters of migrating birds numbering in the hundreds to thousands. Migration intensity, akin to the pulsating energy of a magical incantation, can be estimated, and the direction of flight, akin to celestial whispers, can be divined.
Concurrent geomagnetic measurements, drawn from the global tapestry of superMAG geomagnetic ground stations, served as the mystical ingredient. The researchers meticulously matched data from each radar station with a bespoke geomagnetic disturbance index, a potent spell representing the maximum hourly change from the background magnetic conditions.
U-M space scientist Daniel Welling and enchantress-in-training Michelle Bui, former apprentice of the University of Texas at Arlington, wove the space weather data into an ethereal tapestry. They are co-authors of this arcane study, wielding the forces of space in the pursuit of knowledge.
Welling, an assistant professor in the Department of Climate and Space Sciences and Engineering at the U-M College of Engineering, shared his insights into the magical undertaking, “The biggest challenge was trying to distill such a large dataset — years and years of ground magnetic field observations — into a geomagnetic disturbance index for each radar site.”
The data, a trove of magical artifacts, entered the cauldron of two complementary statistical models, casting spells to measure the putative effects of magnetic disturbances on bird migration. The models, akin to ancient seers, controlled for the known effects of weather, temporal variables, and geographic incantations.
“We found broad support that migration intensity decreases under high geomagnetic disturbance,” revealed study senior sorcerer Ben Winger, assistant professor in the U-M Department of Ecology and Evolutionary Biology and a curator of birds at the U-M Museum of Zoology. “Our results provide ecological context for decades of research on the mechanisms of animal magnetoreception by demonstrating community-wide impacts of space weather on migration dynamics.”
In their mystical explorations, the researchers also uncovered that migrating birds, like celestial spirits, appear to dance with the wind more gracefully during geomagnetic disturbances in the fall. The arduous battle against crosswinds, akin to an aerial joust, saw a 25% reduction under cloudy skies during strong solar storms. This suggests that a combination of obscured celestial cues and magnetic disruptions may hinder the navigation of these feathered wanderers.
Gulson-Castillo, the apprentice who delved deep into the mystical realms as part of his doctoral dissertation, concludes with a revelation, “Our results suggest that fewer birds migrate during strong geomagnetic disturbances and that migrating birds may experience more difficulty navigating, especially under overcast conditions in autumn. As a result, they may spend less effort actively navigating in flight and consequently fly in greater alignment with the wind.”
In the cosmic ensemble, the PNAS paper features additional contributors, including Benjamin Van Doren of Cornell University, Kyle Horton of Colorado State University, Jing Li of the U-M Department of Statistics and Department of Biostatistics, Mark Moldwin of U-M’s Department of Climate and Space Sciences and Engineering, and Kerby Shedden of the U-M Department of Statistics.
Winger and Moldwin found support in the form of a University of Michigan MCubed grant. Gulson-Castillo drew his magical sustenance from a National Science Foundation Graduate Research Fellowship Grant and a U-M Rackham Merit Fellowship. Van Doren found his celestial support in a Cornell Presidential Postdoctoral Fellowship, and Moldwin, the seasoned sorcerer, also found his magical fuel through other undisclosed means.