In April, a massive thunderstorm unleashed a series of tornadoes that tore through the central and southern United States. The 84 twisters decimated homes and buildings, causing more than $1 billion in damage across 17 states. In the wake of the natural disaster, 35 people lost their lives.

Now, scientists say a peculiar event took place just two days before the storm: Flocks of songbirds fled the area en masse. Many golden-winged warblers had just finished a 1,500-mile migration to Tennessee when they suddenly flew south on a 900-mile exodus to Florida and Cuba. At that time, the storm was somewhere between 250 and 560 miles away. The researchers said that the birds somehow knew about the impending storm.

“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,” Henry Streby, a population ecologist from the University of California, Berkeley, said in a statement. He and his research team had been examining the birds’ migratory patterns when they made their discovery.

A golden-winged warbler (Caleb Putnam/Flickr)

Initially, the team was studying if warblers, which weigh the same as four dimes, could carry half-gram geo-locators over long distances. After retrieving data from five of the 20 tagged birds, the team noticed the birds were nowhere near the path they'd expected. Why, the researchers wondered, would these tiny birds travel so far from their already-grueling migratory route? Upon further inspection, the scientists found that the dates the birds broke with the pattern coincided with the beginnings of the storm. In a paper reported today in the journal Current Biology, the team suggests that the birds made their “evacuation migration” because their keen sense of hearing alerted them to the incoming natural disaster.

Huge tornado-spewing storms produce infrasound, or noises at frequencies below 20 hertz that travel for thousands of miles, according to Streby. That sound, which is too low for humans to hear, travels at the same frequency that birds can detect. Previous studies had suggested that pigeons use infrasound to help them navigate, so the scientists linked this ability with the warbler's early escape.

“Biologists had not been looking at the use of infrasound in this way, but it certainly makes sense to me,” Jon Hagstrum, a geophysicist at the U.S. Geological Survey who first linked pigeons and infrasound but was not involved with this study, said in a statement. “We may find that acoustics are a pretty significant way that birds in general view their environment, much like dogs use olfaction and humans use sight.” As of now, the scientists do not know exactly how to use bird behavior to predict future storms, but either way, the public is listening.