Migrating Songbirds Tricked by New Device that Changes the Magnetic Field

It turns out that magnetism may have more of a role to play in bird migration than once expected. Scientists have found new evidence that reed warblers rely on a geomagnetic map to point them in the right direction.

Researchers have long wondered what senses birds rely upon during their migrations. That's why researchers captured Eurasian reed warblers along the Russian coast during their spring migrations. Then, the scientists flew them 1,000 kilometers east of Zvenigorod, putting them off course. However, the birds easily adapted; they simply re-oriented themselves toward their original destination. This made researchers hypothesize that the birds were relying on geomagnetic forces to orient themselves.

In order to test this theory, the researchers created a special magnetic coil system that allowd them to create a homogeneous magnetic field at their coastal field site, where it's easy to catch migratory reed warblers. The system allowed them to manipulate the magnetic field without obscuring the birds' ability to pick up other cues, including the sun, stars, landmarks and scents.

What happened to the birds? It looked as if they relied on the magnetic field far more than their other senses.

"The most amazing part of our finding is that the same birds sitting on the same dune of Courish Spit on the Baltic coast shifted their orientation from their normal migratory directions-northeast-to the northwest after we slightly turned current control knobs on our power supplies," said Dmitry Kishkinev, one of the researchers, in a news release. "All the other sensory cues remained the same for the birds."

The researchers believe that reed warblers track changes in the geomagnetic parameters as they travel during their fall migration. These rules guide the birds on future migrations, and make it possible for them to re-orient themselves if they find they've gotten off track.

The findings are published in the journal Current Biology.

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