For decades, scientists have known that migratory birds rely on the Earth’s magnetic field as one way to help orient themselves and fly the right direction.

But researchers in Germany have documented for the first time that the electromagnetic “noise” produced by modern societies could cause those avian navigation systems to go haywire, according to findings published Wednesday in the journal Nature.

“Basically, anything you plug into a plug will send out electromagnetic noise at some frequency,” said of the paper’s co-authors, Henrik Mouritsen, a professor of neurosensory sciences at University of Oldenburg in Germany. He likened the overall effect in urban environments to an orchestra of potential disruptions at various wavelengths.

What might that mean for the migratory birds trying to maneuver through this busy electromagnetic landscape?

The good news is that they possess other navigation systems, such as relying on the sun and the stars, Mouritsen said. But an overcast day in an urban area teeming with electromagnetic noise could, at least theoretically, cause problems.

“If it doesn’t have any compass available, it might not migrate at all … or it might fly in a random direction,” he said. “We don’t really know.”

Mouritsen and his colleagues stumbled upon the startling findings by chance, and the conclusions were seven years in the making.

Years ago, they were trying to conduct a basic, often-repeated experiment in which European robins are placed in an enclosed, funnel-shaped container lined with scratch-sensitive paper during the migration season. Even inside a cage, without visual cues, the birds typically orient themselves using their internal compass and scratch in the appropriate direction of migration.

But again and again, the birds in Oldenburg couldn’t seem to orient themselves, Mouritsen said. Only when researchers covered the small wooden huts with metal screening and connected it to a grounding wire, blocking man-made electromagnetic noise, did the birds go in the right direction again.