They may be tiny little songbirds, but U.S. researchers have discovered that golden-winged warblers are also keen weather predictors that know when to fly the coop when a dangerous storm is about to descend.

Writing in the journal Current Biology, the scientists say they made their finding by accident last April, as they were testing a new way to track the songbirds. Warblers weigh slightly more than a loonie and the researchers were trying out a new lightweight geolocator placed on the backs of 20 of the birds.

Nine of the birds kept the geolocators on as they migrated thousands of kilometres from South America to their breeding grounds in eastern Tennessee. But the researchers were puzzled when the geolocators revealed that the birds had suddenly taken a detour and headed back south.

About a day later, a huge supercell storm system moved in, spawning 84 tornadoes. In all, 35 people were killed in the devastating storms.

The evacuation saved the warblers, which were able to return to the breeding ground after the storm passed.

While each bird flew on its own path away from the storm, the most curious thing the researchers noticed is that the birds fled more than 24 hours before the storm arrived.

"At the same time that meteorologists on The Weather Channel were telling us this storm was headed in our direction, the birds were apparently already packing their bags and evacuating the area," researcher Henry Streby, a postdoctoral fellow at the University of California, Berkeley, said in a statement.

The research team suspects the birds knew the storm was coming because of their keen hearing. They says it's likely the birds could pick up low frequency "infrasounds" coming from the storm that are below the range of human hearing.

While it's possible the birds picked up on some other cue, Streby said it's known that tornado storms produce strong infrasound that can travel thousands of kilometres and at exactly the same frequency the birds are most sensitive to hearing.

The researchers say their discovery is evidence that even birds that are programmed by instinct to follow annual migratory routes are capable of making unplanned detours to protect themselves.

But the researchers also note that the journey forced the birds to travel a total of 1,500 kilometres in five days, which presumably cost them a great deal of energy that they should have been spending on reproducing.