Songbirds use Earth’s magnetic field as a stop sign during migration

During their migration, Reed Warblers use magnetic information as a “stop sign”, including magnetic tilt telling birds that they have arrived at their destination. Credit: Thomas Miller

A new study published today in Science shed light on how birds return to their breeding grounds after crossing two continents.

The study, part of an international collaboration led by researchers at the University of Oxford and including scientists from the University of Oldenburg, suggests that information extracted from the Earth’s magnetic field tells birds where and when stop migrating. This trick allows them to precisely target the same breeding site year after year from thousands of miles away.

How birds perceive the Earth’s magnetic field has been the subject of intense research. Birds could even “see” magnetic field lines and possibly use this ability to determine both the direction they are facing and where they are.

Dr Joe Wynn, a former University of Oxford and now a researcher at the Avian Research Institute, Germany, said that “as we know more and more about how birds inherit migratory information of their parents how they return to the same site year after year with pinpoint accuracy has remained elusive, so it’s pretty exciting that we were able to find evidence that magnetic signals could be used by songbirds trying to relocate their homes. He began to develop the idea for the study during a stay as a visiting scientist in the research group of biologist Prof. Dr. Henrik Mouritsen at the University of Oldenburg. Mouritsen also participated in the analysis of the study data.

You have arrived at your destination

The team analyzed data from nearly 18,000 warblers to determine if the birds used the earth’s magnetic field to find their breeding site. Reed warblers are tiny songbirds that cross the Sahara desert each year to spend the summer in Europe.

They found that when the Earth’s magnetic field moved slightly, the sites the birds returned to moved with it, suggesting that the birds were heading towards a moving magnetic target. The birds seemed to use the magnetic information as a “stop sign”, with the magnetic tilt in particular telling the birds that they had arrived at their breeding ground.

The job used “ring” data. For almost a century, uniquely numbered metal rings have been attached to the legs of birds all over Europe.

Dr Wynn added that “banding data is a fantastic way to answer questions about migration, simply because it has been collected for so many years over a very large area…and when you look at where the birds were banded and then retrieved, it seems that the reed warblers use a single magnetic coordinate much like a ‘stop sign’; when they reach the correct magnetic field value, they stop migrating.”

Why use the magnetic field to inform return migration?

Dr Wynn explains that “The magnetic information seems to be quite stable, which means that the magnetic field does not change much at any given location from year to year. Aiming for a specific magnetic value during migration can then have some difficulty. sense, and the signal we think the birds are using, the tilt, seems to be the most stable aspect of the magnetic field. We think this gives the birds the best chance of getting back to the breeding site.

In conclusion, Dr Wynn said, “The transcontinental migration of birds that weigh less than a teaspoon is remarkable for many reasons, but the ability to pinpoint the exact breeding site of half the world is -being the most extraordinary aspect of all. The fact that we can study this using data collected by scientists and bird watchers is extremely exciting, and we hope that this use of citizen science data will inspire others to going out, birdwatching and being enthusiastic about science more generally.

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More information:
Joe Wynn et al, Magnetic stop signs signal the arrival of a European songbird at the breeding site after migration, Science (2022). DOI: 10.1126/science.abj4210

Provided by University of Oldenburg

Quote: Magnetic Navigation: Songbirds use Earth’s magnetic field as a stop sign during migration (January 28, 2022) Retrieved March 12, 2022 from -field-migration.html

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