6 May 2015
Just over a year ago a violent storm system spawned 84 tornadoes that ripped through the central and southern U.S. on April 27-30, 2014. Because of the storms’ advanced warning, ornithologists learned an amazing thing about birds.
In the previous year, Dr. Henry Streby and researchers from the Universities of Tennessee and Minnesota had placed geolocators on 20 golden-winged warblers nesting in the northeast mountains of Tennessee.
The tiny devices had recorded information while the warblers migrated and now, in late April, it was time to recapture the birds and retrieve the data.
During that fateful week in April, the researchers had found 10 of the warblers in Tennessee and were about to capture them when they learned of the storm and left the mountain to wait it out.
The storm was very bad! It roared through Kansas and Arkansas on April 27, generated this radar image in Tennessee on April 28 (click image for a closeup), and then dumped heavy rain on April 30.
When the violent weather was over, the researchers went back up the mountain and captured five golden-winged warblers wearing geolocators. In the months that followed they downloaded and processed the data to chart the birds’ course.
And here’s the amazing thing: The data showed that the birds spent the winter in Colombia as expected, but there was an aberration just before the geolocators were retrieved. One to two days before the tornadoes struck, all five birds sensed the storms were coming and evacuated 400 miles southward — all the way to the Gulf of Mexico, just outside the danger zone. When the storms were over, they flew back to Tennessee and were back on territory by May 2.
The tornadoes’ low-frequency sound gave the warblers a long-distance cue. They heard it and fled! The researchers speculate that other birds do this, too.
Read more here in BBC Science News.
(photos from Wikimedia Commons. Click on the images to see the originals. F5 Tornado in Elie, Manitoba, June 2007, by Justin Hobson. Golden-winged warbler by Andy Reago. Radar image from National Weather Service of F3 tornado in Lincoln-Moore County, TN, April 28, 2014)
p.s. To see the size of a geolocator on a warbler, here’s a blackpoll warbler wearing a geolocator.