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.

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.