'Bird has flown': Warblers predict tornadoes, escape before they hit, report shows
Birds can predict tornadoes and hurricanes and move away before the disaster unfolds, US scientists discovered conducting a research on golden-winged warblers.
Tracking a population of golden-winged warblers, a research team
led by UC Berkeley ecologist Henry Streby revealed that birds in
the mountains of eastern Tennessee escape their breeding grounds
one or two days prior to the arrival of powerful storms.
A storm system which swept through the central and southern US in
April caused up to 84 tornadoes and killed 35 people. The
findings are published in the journal Current Biology.
“It is the first time we’ve documented this type of storm
avoidance behavior in birds during breeding season,” Streby
told UC Berkley news center.
“We know that birds can alter their route to avoid things
during regular migration, but it hadn’t been shown until our
study that they would leave once the migration is over and they’d
established their breeding territory to escape severe
weather,” he noted.
The warblers in the latest study flew up to 1,500km to avoid the
storm. They smartly returned home as soon as the disaster passed
and the picture cleared.
The birds, with their trademark gray plumage spiced up by patches
of yellow on the head and wings, fled while the storm was about
900km away, before changes in atmospheric pressure and wind
speed. It means that when meteorologists were only announcing
that the storm was on its way, the birds were already
"packing their bags and evacuating the area,” Streby
explained.
There's currently a real need to study the golden-winged
warblers, their population only 5 percent of historic levels in
the Appalachians due to habitat loss and hybridization with other
species.
The researchers were testing whether a tiny bird, weighing some 9
grams, could manage to carry a half-gram geolocator throughout
the year. To obtain the tracking data, they had to retrieve as
many geolocators as possible from the 20 birds that had been
originally tagged. The study results come from five geolocators.
According to Streby, these warblers are the smallest bird species
ever marked. The fact that any geolocators had returned at all
was a great relief, he mentioned.
Studying the data on the geolocators, the researchers detected
anomalies in the geographical locations for the birds from April
26 to May 2. It turned out that the birds changed course and flew
back from their breeding grounds in Tennessee’s Cumberland
Mountains to the Gulf coast. At first the scientists thought
there was a mistake in the data. When they double-checked and
realized it wasn't the case, they started looking for a better
explanation.
Streby said the supercell storm came to mind simply because they
also had to move to a hotel to wait it go away.
However, the wise birds had gone long before, when local weather
conditions were still normal. This made the researchers wonder
how they got their early alert.
Infrasound appeared to be the answer. Acoustic waves, which occur
at frequencies below 20 hertz, fall into the infrasound range
below the limits of human hearing, but birds and other animals
can hear infrasound. Tornadoes are also known to produce powerful
infrasound, so the ability of birds to forecast deadly storms
could become extremely important.
“There’s growing research that shows that tornadoes are becoming
more common and severe with climate change, so evasive actions
like the ones the warbler took might become more necessary,”
Streby said. “It could come at a cost, though, since such
actions place added energetic and reproductive stress on
populations that are already struggling.”
