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It’s well known that many species, including birds, rely on magnetoreception during migration. But these internal compasses can be disrupted during powerful solar storms.
A new study shows how much solar storms impact migratory birds in North America, and estimates a 9 to 17 percent decrease in migration during such storms.
This is particularly important now, as the Sun will enter its solar maximum in 2024 and increased solar storms will be likely.
It’s well known that migratory birds—who, in some cases, travel the entire globe every year—rely on magnetic fields to point them toward their seasonal home. But those fields aren’t always reliable. Solar storms and other space weather events can knock out satellite navigation and avian navigation in equal measure, and when the Sun reaches its solar maximum (the greatest period of activity in its 11-year solar cycle) around mid-to-late 2024, such geomagnetic disruptions will be even more frequent.
To figure out just how widespread this space weather-induced confusion can be, scientists from the University of Michigan studied 23 years of migration data across the U.S. Great Plains—a migratory corridor that stretches from Texas to North Dakota. Gathering more than 3 million images of spring and fall migrations from 37 NEXRAD stations located within the flyway, the team analyzed the migration pattern of various types of birds like Passeriformes (perching birds), Charadriiformes (shorebirds), and Anseriformes (waterfowl). This data was combined with concurrent geomagnetic data from superMAG, which is a worldwide network of geomagnetic ground stations.
This analysis, published in a study earlier this month in the journal Proceedings of the National Academy of Sciences (PNAS) revealed a 9 to 17 percent reduction in both fall and spring migrations during space weather events. This also includes increased vagrancy, a term used to describe a bird becoming lost during the migratory process. Vagrancy can occur during intense tropical storms, such as hurricanes, which can physically blow birds off course. But, as another study published earlier this year discovered, geomagnetic disturbances can also be a culprit.
“We found broad support that migration intensity decreases under high geomagnetic disturbance,” senior author Ben Winger, assistant professor in the UM Department of Ecology and Evolutionary Biology and a curator of birds at the UM Museum of Zoology, said in a press release. “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.”
Crunching this immense amount of data—which one scientist involved in the process referred to as “the biggest challenge” of the study—the scientists discovered that the migratory birds impacted by geomagnetic disturbances tended to drift on the wind during solar storms rather than fight against crosswinds to travel to the correct destination. This was particularly pronounced in the fall when solar storms and cloudy skies combined to cause a 25 percent decrease in such “effort flying,” according to the study.
“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,” UM PhD student and study lead author Eric Gulson-Castillo said in a press statement. “As a result, they may spend less effort actively navigating in flight and consequently fly in greater alignment with the wind.”
These results are particularly concerning now, as the Sun will soon enter its solar maximum. Scientists have already said that our star’s activity is smashing forecasts, and could be more active than at any point we’ve seen in at least the past 20 years. And it’s not just the birds. Other vulnerable species, such as whales, also rely on some level of magnetoreception to migrate. Understanding how these species will be impacted by solar storms could help us provide a solution that could save them from the worst of these effects.
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