Authors: Eric R. Gulson-Castillo, Benjamin M. Van Doren, Michelle X. Bui, Kyle G. Horton, Jing Li, Mark B. Moldwin , Kerby Shedden, Daniel T. Welling, and Benjamin M. Winger
Year: 2023
Publication: Proceedings of the National Academy of Science
Publication Link: https://www.pnas.org/doi/10.1073/pnas.2306317120
Keywords: bird migration, space weather, geomagnetic disturbances, radar
Abstract: Space weather, including solar storms, can impact Earth by disturbing the geomagnetic
field. Despite the known dependence of birds and other animals on geomagnetic cues for
successful seasonal migrations, the potential effects of space weather on organisms that
use Earth’s magnetic field for navigation have received little study. We tested whether
space weather geomagnetic disturbances are associated with disruptions to bird migration
at a macroecological scale. We leveraged long-term radar data to characterize the
nightly migration dynamics of the nocturnally migrating North American avifauna over
22 y. We then used concurrent magnetometer data to develop a local magnetic disturbance
index associated with each radar station (ΔBmax), facilitating spatiotemporally
explicit analyses of the relationship between migration and geomagnetic disturbance.
After controlling for effects of atmospheric weather and spatiotemporal patterns, we
found a 9 to 17% decrease in migration intensity in both spring and fall during severe
space weather events. During fall migration, we also found evidence for decreases in
effort flying against the wind, which may represent a depression of active navigation
such that birds drift more with the wind during geomagnetic disturbances. Effort flying
against the wind in the fall was most reduced under both overcast conditions and high
geomagnetic disturbance, suggesting that a combination of obscured celestial cues and
magnetic disturbance may disrupt navigation. Collectively, our results provide evidence
for community-wide avifaunal responses to geomagnetic disturbances driven by space
weather during nocturnal migration.