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Two days before a storm hit Tennessee that spawned 84 tornadoes and killed 35 people earlier this year, there was a mass exodus of birds. 

Golden-winged warblers that live in the mountains of eastern Tennessee were spotted fleeing their breeding grounds ahead of the arrival of the powerful supercell storm.

And the discovery was made by accident while researchers were testing whether the warblers - which weigh less than two small coins - could carry geolocators on their backs.

Warning call: While tracking a population of golden-winged warblers, a research team led by ecologist Henry Streby at the University of California, Berkeley, discovered that the birds in the mountains of eastern Tennessee fled their breeding grounds one to two days ahead of the arrival of powerful supercell storms

It turned out they could. 

With a big storm brewing, the birds were seen taking off from their breeding ground, where they had only just arrived, as part of an unplanned migratory event.

The birds were alerted when the storm was 560 miles (900km) away, causing them to flee to Cuba before making the return trip once the storm had passed.

Overall, the warblers travelled 930 miles (1,500 km) in just five days to avoid the deadly storms.

Dr Henry Streby, of the University of California, Berkeley, said: 'The most curious finding is that the birds left long 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.'

Dr Streby and his colleagues found the birds fled from their breeding territories more than 24 hours before the arrival of the storm.

Trouble brewing: Overall, the warblers travelled 930 miles (1,500 km) in just five days to avoid the deadly storms. Pictured is the Super Typhoon Hagupit shown earlier this month. Experts suspect that the birds did it by listening to infrasound associated with the severe weather, at a level well below the range of human hearing

The researchers suspect that the birds did it by listening to infrasound associated with the severe weather, at a level well below the range of human hearing.

Dr Streby said: 'Meteorologists and physicists have known for decades that tornadic storms make very strong infrasound that can travel thousands of kilometres from the storm.'

He said while the birds might pick up on some other cue, the infrasound from severe storms travels at exactly the same frequency the birds are most sensitive to hearing.

The findings, published in the journal Current Biology, show that birds that follow annual migratory routes can also take off on unplanned trips at other times of the year when conditions require it.

Dr Streby said: 'Our observation suggests birds aren't just going to sit there and take it with regards to climate change, and maybe they will fare better than some have predicted.

'On the other hand, this behaviour presumably costs the birds some serious energy and time they should be spending on reproducing.'

Now Dr Streby's team plan to deploy hundreds of geolocators on the golden-winged warblers and related species across their entire breeding range to find out where they spend the winter and how they get there and back.

He added: 'I can't say I'm hoping for another severe tornado outbreak, but I am eager to see what unpredictable things happen this time.'

With a big storm brewing, the birds took off from their breeding ground in the Cumberland Mountains (shown on this map) of eastern Tennessee, where they had only just arrived, during an unplanned migratory event