It is well known that the birds and other animals depend on the Earth’s magnetic field for very long-distance flights But how do they affect seasonal migrations? periodic interruptions of the planet’s magnetic fieldHow much do solar flares and other bursts of energy affect the reliability of biological navigation systems?
Researchers at the University of Michigan (USA) tested it using data sets from US Doppler weather radar stations and ground-based magnetometers (devices that measure the strength of local magnetic fields). Relationship between geomagnetic disturbances and changes in night bird migrations.
Like this, A 9% to 17% decrease in the number of migratory birds was detectedBoth in spring and autumn during severe space weather events. It has been observed that birds that choose to migrate during such events have more difficulty finding their way, especially in cloudy weather in autumn.
According to researchers, this discovery Proceedings of the National Academy of Sciencesprovides evidence of hitherto unknown relationships between the dynamics of nocturnal bird migration and geomagnetic disturbances.
“Our findings highlight how animals’ decisions depend on environmental conditions, including conditions we as humans cannot perceive, such as geomagnetic disturbances, and that these behaviors influence animal movement patterns at the population level,” said Eric Gulson, lead author of the study. Castillo, from the UM Department of Ecology and Evolutionary Biology.
The Earth’s magnetic field is periodically affected by solar flares. It can cause colorful auroras and sometimes disrupt satellite communications, human navigation systems, and electrical networks.
It turns out that birds that choose to migrate during such events have more difficulty finding direction.
But little is known about how these disturbances affect animals that depend on the Earth’s magnetic field for migratory guidance and navigation. Experimental studies published in recent years show that: Birds, sea turtles, and other organisms are affected by small changes in magnetic tilt, intensity, and declination. When it comes to orienting yourself and developing navigation maps.
A recent study examined millions of bird banding records and found that geomagnetic disturbances were linked to a higher incidence of migratory birds “wandering,” i.e., lost in migration.
However, most previous studies have focused on the geographic range, duration and number of species studied. The newly published study, by contrast, uses a dataset from 23 years of bird migration. In the Great Plains of the United States to provide more extensive information.
Researchers They used images collected from 37 radar stations NEXRAD is in the central flyway of the U.S. Great Plains, a major migration corridor. The migration route stretches more than 1,500 kilometers across the United States, from Texas to North Dakota.
The research team chose this relatively flat region to minimize impacts from mountainous topography or the ocean and Great Lakes coastline. The final data sets included 1.7 million radar scans from the fall and 1.4 million from the spring.
The nocturnal migratory bird community in this region consists mainly of various bird species (passerines, 73% of species), such as thrushes and warblers; shorebirds such as sandpipers and plovers (charadriiformes, 12%); and waterfowl such as ducks, geese, and swans (anseriformes, 9%).
NEXRAD radar scanners They detect groups of hundreds to thousands of migratory birds and allow estimation of migration intensity, that is, measuring the number of birds in each group and their flight direction. Simultaneous geomagnetic measurements were also accessed at: superMAG, a global collection of geomagnetic ground stations. Data were collected from magnetometric stations close to weather radar sites.
The researchers compared data from each radar station with a specific geomagnetic disturbance index that represents the maximum time variation relative to background magnetic conditions. UM scientists Daniel Welling and Arlington Michelle Bui compiled the space weather data and designed the geomagnetic disturbance index.
Less migration with more magnetic activity
The resulting data were entered into two complementary statistical models to quantify the putative effects of magnetic disturbances. in bird migration. The models controlled for known effects of climate, temporal variables such as weather, as well as geographic variables such as longitude and latitude.
“We saw this Migration intensity decreases under high geomagnetic disturbance” said the study’s lead author, Ben Winger, an assistant professor in the UM Department of Ecology and Evolutionary Biology.
“Our results demonstrate the effects of space climate on community-wide migration dynamics, providing ecological context for decades of research on animal magnetic sensing mechanisms.”
“We found that migration intensity decreased under high geomagnetic disturbance.”
Researchers also found: Migratory birds appear to drift more frequently during geomagnetic disturbances (due to wind) in the fall, instead of making great efforts to combat crosswinds.
Downwind flight effort reduced by 25% under cloudy skies during strong solar storms In autumn, this suggests that the combination of overcast skies and magnetic disturbances may make navigation difficult for migratory birds.
“Our results suggest that fewer birds migrate during strong geomagnetic disturbances and that migratory birds may have more difficulty navigating, especially in cloudy conditions in autumn,” said Gulson-Castillo, who conducted the study as part of her doctoral thesis. said.
Reference work: https://www.pnas.org/doi/10.1073/pnas.2306317120
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