While tracking a population of golden-winged warblers (Vermivora chrysoptera) in Tennessee in April 2014, a team of ornithologists led by Dr Henry Streby of the University of California, Berkeley discovered that the birds fled their breeding grounds days ahead of the arrival of severe, tornado-producing storms.

“The most curious finding is that the birds left long before the storm arrived (more than 24 hours ahead). 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,” said Dr Streby, who is the lead author of a paper published in the journal Current Biology.

With a big storm brewing, the warblers took off from their breeding ground in the Cumberland Mountains of eastern Tennessee, where they had only just arrived, for an unplanned migratory event.

The birds, according to the scientists, traveled 1,500 km in five days to avoid the tornadic storms.

“The warblers in our study flew at least 1,500 km total to avoid a severe weather system. They then came right back home after the storm passed,” Dr Streby said.

“Notably, the birds fled while the storm was still 400-900 km away, and local environmental cues to inclement weather – including changes in atmospheric pressure, temperature and wind speed – were largely absent.”

The findings 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.

“Our observation suggests that 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 behavior presumably costs the birds some serious energy and time they should be spending on reproducing,” Dr Streby noted.

Scientists have known for decades that tornadoes produce very strong infrasound – acoustic waves that occur at frequencies below 20 Hz, which is below the normal limits of human hearing.

Birds and other animals, however, have been shown to hear infrasound and the new study presents convincing evidence that birds use it to remotely detect storms.

“The ability of birds to forecast massive storms could become increasingly important in the decades ahead,” the scientists said.

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Henry M. Streby et al. Tornadic Storm Avoidance Behavior in Breeding Songbirds. Current Biology, published online December 18, 2014; doi: 10.1016/j.cub.2014.10.079