Birds, like Eurasian reed warblers, rely on Earth's geomagnetic grid to point them in the right direction during spring migrations, a new study confirms.

In order to better understand what senses birds rely on when traveling, scientists captured Eurasian reed warblers along the Russian coast during their spring migrations and then flew them 1,000 kilometers off course to observe whether they'd be able to re-orient themselves toward their original destination.

The birds passed the test with flying colors and weren't the the slightest bit fazed.

Next, scientists tested whether the birds could be navigating using Earth's geomagnetic field, which is generated by electric currents produced from convection forces within its core. 

To test this idea, researchers created a special boxed system that allowed them to manipulate magnetic fields without obscuring the birds' ability to pick up on other cues, such as the sun, stars, landmarks and even scents.

The birds were placed inside the magnetic system – essentially a cage with it's own magetic field – to disorient the birds. But even these birds were able to re-orient themselves and quickly flew in the direction of their breeding destinations, just as the first test had done when they were physically displaced. 

"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 direction – northeast – to the northwest after we slightly turned current control knobs on our power supplies," Dmitry Kishkinev, from the Queen's University Belfast, said in the release. "All the other sensory cues remained the same for the birds."

All of this has led researchers to conclude that – these birds but probably most birds – rely more heavily on interpreting Earth's magnetic field than their other senses, tracking changes in the geomagnetic parameters as they travel during their first fall migration and using these parameters as a "rule of thumb" for future trips. This special innate navigation sense – which is also evident in spiny lobsters and sea turtles – helps them stay on course. 

Study findings were recently published in the journal Current Biology.  

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