Space Weather Events Cause 9 To 17% Reduction in Bird Migration, Study Says

Migratory birds that rely on the Earth's magnetic field to navigate become disoriented during space weather events such as solar flares, according to a new study.

Nocturnally migratory species, such as geese and swans, sandpipers, and thrushes, use the Earth's magnetic field to guide them on their long seasonal migrations.

However, when space weather disturbs the magnetic field, fewer birds prefer to fly.

Those that do frequently become disoriented or lost as a result of the disturbances to their navigation.

Environmental conditions

The new findings published in the Proceedings of the National Academy of Sciences provide correlational evidence for previously unknown links between nighttime bird movement dynamics and geomagnetic disturbances.

Researchers from the University of Michigan and their colleagues used enormous, long-term datasets from US network networks.

Doppler weather radar stations and ground-based magnetometers are used to investigate a probable relationship between geomagnetic disturbances and interruptions to nocturnal bird migration.

During severe space weather events, they discovered a 9-17% decline in the number of migrating birds in both spring and fall.

And the birds that choose to migrate during such occurrences appeared to have more difficulties navigating, especially in cloudy fall weather.

"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.

Effort flying

This latest study examined a 23-year dataset of bird migration across the United States' Great Plains, a vast plateau that runs the length of the country east of the Rocky Mountains, to reveal new insights.

The photos were obtained at 37 radar stations in the central flyway of the US Great Plains, a major migratory route.

The plains run for almost a thousand miles down the middle of the country, from Texas in the south to North Dakota near the Canadian border.

The study's final result was 1.7 million autumn radar scans and 1.4 million spring radar scans.

The researchers compared data from each radar station to a developed geomagnetic disturbance index that represented the maximum hourly change from background magnetic conditions.

The data trove collected by the team was loaded into two complimentary statistical models to assess the effects of magnetic disturbances on bird migration. The models accounted for weather, temporal variables such as time of day, and geographic variables such as longitude and latitude.

The results showed that under cloudy skies during large solar storms in the autumn, 'effort flying' against the wind was reduced by a quarter, implying that a combination of obscured celestial signals and magnetic disruption may hamper the birds' navigation.

"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 Gulson-Castillo.

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