For thousands of years, humans have used the behaviour of birds to forecast the weather. But are any of these predictions grounded in reality? Or are they simply old wives’ tales that should be confined to almanacs and collections of folklore.
Little scientific research has been undertaken to find out, but in recent years a couple of small studies have found that birds may indeed be able to predict storms.
In 2014 a team from the University of California discovered quite by accident that a group of golden-winged warblers fled their US breeding grounds in the Cumberland Mountains, north-eastern Tennessee, well in advance of devastating supercell storms that would spawn at least 84 recorded tornadoes and kill 35 people.
The researchers were testing wither the tiny songbirds would be able to fly with geolocators attached to their backs. The birds had only just returned from their wintering grounds in South America when they took off again in an unplanned migration to avoid the massive storm which arrived 24 hours later.
Interestingly they appeared to act independently of each other with one bird making its way to Cuba. Others flew to Florida’s Gulf Coast, but all the birds not only detected the storm but also knew where to fly to avoid it. They either travelled southeast in front of the storm, and then let it go by, or they moved behind it. And this was despite having just completed a migration of more than 2,500 km.
They began the evacuation when the tornadoes were still 900 km away and while weather conditions in the mountains of Tennessee were normal for the time of year with no apparent changes in atmospheric pressure, or temperature and wind speed.
After the storm had blown over, the golden-winged warblers returned to their breeding grounds where the researchers recaptured them. The geolocators indicated that they had flown at least 1,500 km in total.
About a decade earlier, a marbled godwit fitted with a satellite transmitter, made its usual migration from Alberta to Baja California for the winter where it stayed for several weeks. Just before the arrival of Hurricane John, which caused extensive damage across much of the Pacific coast of Mexico, the bird flew to Texas and back, apparently to avoid the storm.
The report was published in the ornithology journal, North American Birds, and included the observation, “As almost nothing is known about individual birds’ responses to approaching tropical cyclones, this bit of information is most intriguing.”
A further study in 2018 showed that birds may have an even more remarkable weather-forecasting ability, and that they are able to predict storms not just days, but months in advance.
Dr. Christopher Heckscher at Delaware State University had been studying veeries, a small species of North American thrush, for 20 years. He had been collecting data to find out how the bird’s nesting habits correlate to the severity of hurricane seasons.
Veeries nest in forests in the north of the United States and southern Canada and spend their winters in the Amazon region in South America. During their migration they must contend with the storms around the Atlantic Ocean and Gulf of Mexico.
Veeries tend to produce just one successful brood a year with early nests often failing due to predation or bad weather. They’ll continue trying until they are able to hatch chicks or if it gets too late in the season they’ll stop altogether, moult into fresh feathers, and leave their breeding grounds for the winter.
Dr. Heckscher found that in the years that had a more severe hurricane season, the veeries nesting in Delaware ended their breeding season and completed their annual moult early so they could set off on their migration south earlier and avoid the worst of the storms.
He admits that the dataset of just a few pairs a year of one species of bird is small, but the data covers many years, and the correlation is statistically strong. And although, he does not know how the birds are able to predict hurricanes so far in advance he thinks they may be aware of precipitation patterns linked to the El Niño and La Niña cycles that have an impact on hurricane activity.
In 2018 Dr. Heckscher made a prediction based on the veeries’ behaviour that the hurricane season of that year would be stronger than average with an accumulated cyclone energy (ACE) which measures the intensity of the storms of between 70 and 150. Meteorologists predicted a below-average season with an ACE of between 60 and 130.
The actual ACE for the season was 129, right in the middle of the birds’ and Dr. Heckscher’s forecast.
As for the golden-winged warblers, again scientists aren’t certain how the birds could sense there was a storm coming, but they think that the birds were able to pick up infrasound associated with severe weather.
Infrasound is sound below 20 Hz, which is well below the level of the range of human hearing, and is what elephants and whales use for communication. There is evidence that birds use infrasound to help them navigate and so it is not beyond the realms of possibility that they also use signals from infrasound to understand when bad weather is coming their way.