Geomagnetic disturbances from solar flares throw nocturnal birds off migratory course

Researchers at the University of Michigan have found that geomagnetic disturbances, often a result of solar flares and other energetic outbursts, can significantly impact the migratory patterns of nocturnal birds.

Earth’s magnetic field 

Birds, and numerous other animals, depend on the Earth’s magnetic field for long-distance navigation during their seasonal migrations. However, the impact of periodic disruptions in this magnetic field have remained largely unknown.

The researchers analyzed information stored in long-term datasets from networks of U.S. Doppler weather radar stations and ground-based magnetometers. They found a startling link between space weather events and nocturnal bird migration. 

What the researchers learned 

The findings reveal a substantial 9-17% reduction in the number of migrating birds during significant space weather occurrences, observable in both spring and autumn seasons. 

Furthermore, birds that did choose to embark on their migration journeys during such geomagnetic disturbances faced increased navigational challenges, particularly in overcast conditions during the fall.

Uncharted relationships 

The research sheds light on previously uncharted relationships between bird migration and geomagnetic disturbances. 

“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,” said study lead author Eric Gulson-Castillo, a doctoral student in the U-M Department of Ecology and Evolutionary Biology.

Impacts on wildlife

While it’s understood that Earth’s magnetic field experiences regular disturbances from solar outbursts, which manifest as breathtaking auroras and can interrupt satellite communications and power grids, the implications of these disturbances on wildlife remained largely speculative. 

Previous research has suggested a potential link. For example, a study analyzing millions of bird banding records found increased incidents of migratory bird “vagrancy” – or birds getting lost during migration – correlating with geomagnetic disruptions.

These earlier studies, however, had a limited scope as far as their duration, geographic extent, and the number of bird species examined.

The Great Plains

The current study involved a 23-year dataset spanning the vast stretch of the U.S. Great Plains, providing an unprecedented look at the migration patterns on a larger scale. 

The chosen region for data collection, the central flyway of the U.S. Great Plains, is a significant migratory corridor extending over 1,000 miles from Texas to North Dakota. The area was chosen for its relatively flat topography, eliminating influences from mountains or extensive coastlines.

Focus of the study

The research team accessed images from 37 NEXRAD radar stations. These radar scans detected groups of migrating birds numbering in the hundreds to thousands, enabling estimations of migration intensity and flight directions. 

The data was then compared with concurrent geomagnetic measurements obtained from superMAG, a global collection of geomagnetic ground stations.

Geomagnetic disturbances 

Ben Winger, the study’s senior author, noted the broad agreement in findings that migration intensity is diminished by intense geomagnetic disturbances. 

“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,” said Winger.

Drifting in the wind

Further observations revealed that birds seem to drift more with the wind during geomagnetic disturbances, especially in the fall. 

Strong solar storms under cloudy conditions reduced “effort flying” against the wind by 25%, suggesting that the combined effects of blocked celestial cues and magnetic disruptions might be impacting navigation.

“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,” said Gulson-Castillo. “As a result, they may spend less effort actively navigating in flight and consequently fly in greater alignment with the wind.”

The study is published in the journal Proceedings of the National Academy of Sciences.

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