Birds Flee Before the Storm
Scientists tracking golden wing warblers with geolocators made an unexpected discovery. One to two days prior to a major storm hitting the area, the birds flew south out of the path of the storm. They apparently could hear the storm coming from hundreds of miles away.
Major storms are devastating to small birds. It would therefore be a huge adaptive advantage if they could avoid tornadoes and other such storms. Henry Streby and his colleagues at the University of California, Berkeley were performing a pilot study of migratory warblers in the Cumberland Mountains of eastern Tennessee. They tracked the migration of 10 birds to Columbia for the winter, and their return to nest in the summer in the Cumberland Mountains.
Just as the 10 birds they were tracking were settling into their summer nests, they left, flying south to the Gulf of Mexico. Then a major storm hit, with 84 confirmed tornadoes, killing 35 people. After the storm was over the researchers were able to recapture five of the warblers and interrogate their tracking devices. It turns out they left 1-2 days prior to the storm hitting the area, when the closest tornadoes were still hundreds of miles away.
Streby speculates that the warblers were able to hear the distant infrasound rumble of the storms, at frequencies too low for humans to hear.
The tracking devices measure light, and then infer latitude based on the duration of light and dark exposure. Streby cautions that shady may throw off the measurements, but also reports that the changes in light exposure were smooth, consistent with the birds flying south rather than a shading artifact.
Current Biology, Streby et al.: “Tornadic Storm Avoidance Behavior in Breeding Songbirds”