Golden-winged warblers apparently knew in advance that a storm that would spawn 84 confirmed tornadoes and kill at least 35 people last spring was coming, according to a report published online on December 18, 2014 in Current Biology. The birds left the scene well before devastating supercell storms blew in. The discovery was made quite by accident while researchers were testing whether the warblers, which weigh "less than two nickels," could carry geolocators on their backs. It turns out they can, and much more. With a big storm brewing, the birds took off from their breeding ground in the Cumberland Mountains of eastern Tennessee, where they had only just arrived, for an unplanned migratory event. All told, the warblers travelled 1,500 kilometers in 5 days to avoid the historic tornado-producing storms. "The most curious finding is that the birds left long before the storm arrived," says Dr. Henry Streby of the University of California, Berkeley. "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. The birds fled from their breeding territories more than 24 hours before the arrival of the storm, Dr. Streby and his colleagues report. 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. "Meteorologists and physicists have known for decades that tornadic storms make very strong infrasound that can travel thousands of kilometers from the storm," Dr. Streby explains. While the birds might pick up on some other cue, he adds, the infrasound from severe storms travels at exactly the same frequency the birds are most sensitive to hearing.
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