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Early Warbler System

Supercell storm

A windmill standing alone against a supercell thunderstorm. Photo by Stephen Corfidi

Apparently birds—in this case, golden-winged warblers—know big storms are headed their way several days before the storms actually arrive. According to a story in the UC Berkeley News Center, a research team led by a UC Berkeley ecologist discovered that warblers in the mountains of eastern Tennessee fled their breeding grounds one to two days ahead of the arrival of devastating supercell storms in April 2014. The storms spawned dozens of tornados, killing more than 30 people.

The discovery was accidental: the golden-winged warblers were part of a migration study, and were being tracked by miniature GPS devices attached to their backs. The scientists knew that birds can change their route to avoid weather disruptions during regular migration, but had no idea they’d leave their established breeding territory to avoid severe weather.

The birds fled the scene when the storm was about 300 miles away—even before the air pressure dropped and the winds picked up. And they went some distance: according to the study, the warblers flew over 900 miles as they avoided the weather system. They returned to their breeding grounds just after the storm passed.

How did they know? Scientists have known for decades that tornadoes produce very strong infrasound, and that birds can hear and respond to infrasound frequencies. The researchers’ theory is that the warblers picked up the storms’ infrasound, interpreted it correctly, and got out of Dodge, so to speak.

Golden-winged warbler

Golden-winged warbler
Photo by Andy Reago (Golden-winged Warbler) [CC BY 2.0], via Wikimedia Commons

An adult golden-winged warbler weighs about 9 grams (approximately the weight of four dimes). The researchers were studying whether these small birds could successfully carry a geolocator that weighs half a gram. Turns out they can. The researchers originally tagged 20 birds, and retrieved data about the period before and after the storms from five of the birds’ geolocators.

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