Five years ago, French navy officer Jérôme Chardon was listening to a radio program about the extraordinary journey of the bar-tailed godwit, a bird that migrates 14,000 kilometers between New Zealand and Alaska. In his job as the coordinator of rescue operations across Southeast Asia and French Polynesia, Chardon understood better than most how treacherous the journey would be, as ferocious storms frequently disrupt Pacific island communities. Yet, somehow, bar-tailed godwits routinely pass through the area unscathed. Chardon wondered whether learning how godwits navigate could help coastal communities avoid disaster. Could tracking birds help save lives?
This past January, a team from France’s National Museum of Natural History (NMNH), funded primarily by the French Ministry for the Armed Forces, began experiments designed to test Chardon’s idea. Researchers with the new Kivi Kuaka project, led by Frédéric Jiguet, an ornithologist at NMNH, equipped 56 birds of five species with cutting-edge animal tracking technology. The French navy ferried the team to remote atolls and islands in French Polynesia, where the scientists attached tags using ICARUS tracking technology. These tags transmit the birds’ locations to the International Space Station, which bounces the data back to scientists on Earth who can then follow the birds as they forage, migrate, and rest—all the while waiting to see how the birds respond to natural disasters.
The Kivi Kuaka project is focusing on birds’ ability to hear infrasound, the low-frequency sound inaudible to humans ¬that the researchers believe is the most likely signal birds would use to sense storms and tsunamis. Infrasound has myriad sources, from lightning strikes and jet engines to the songlike vocalizations of rhinoceroses. Even the Earth itself generates a continuous infrasonic hum. Though rarely measured, it is known that tsunamis generate infrasound, too, and that these sound waves travel faster than the tsunami wave, offering a potential window to detect a tsunami before it hits.
There is some evidence that birds dodge storms by listening to infrasound. In a 2014 study, scientists tracking golden-winged warblers in the central and southeastern United States recorded what’s known as an evacuation migration when the birds flew up to 1,500 kilometers to evade an outbreak of tornadoes that killed 35 people and caused more than US $1-billion in damage. The birds fled at least 24 hours before any foul weather hit, leaving the scientists to deduce they had heard the storm system from more than 400 kilometers away.
The idea that birds avoid tsunamis, on the other hand, is based primarily on anecdotal evidence from the 2004 Indian Ocean tsunami, when survivors reported birds traveling inland in advance of the deadly wave. Jiguet says the idea makes sense from an evolutionary perspective, because birds that survive tsunamis would be more successful at reproducing.
If Kivi Kuaka’s birds are able to perceive infrasound generated by Pacific storms or tsunamis, the scientists suspect the birds will move to avoid them. Tracking that behavior, and learning to identify tsunami-specific bird movements if they exist, may help the team develop an early warning system, Jiguet says.
For the Kivi Kuaka team, tsunamis are the main interest; satellites and computer models already forecast hurricanes and typhoons accurately. But infrasound-producing storms are a useful test because they’re more common than tsunamis. If their tagged birds evade them from afar, Jiguet says, it provides further evidence that they could serve as tsunami sentinels.
The team plans on tagging hundreds more birds across the Pacific to prepare for a potential tsunami. “I think if there is one wave that spreads across islands, yes, we should get data from different species at different locations to see if there are some convergent behaviors,” says Jiguet. “That would definitely say it’s worth continuing to tag and to develop local systems to better analyze this.”
Tsunami scientist Eddie Bernard, the former head of the US National Oceanic and Atmospheric Administration’s Pacific Tsunami Warning Center and Pacific Marine Environmental Laboratory, has seen his fair share of ideas for forecasting tsunamis. He thinks the real hope for tsunami-warning technology is the one he helped develop, and which already dots coastlines today. Known as deep-ocean assessment and reporting of tsunamis (DART), the system relies on a highly sensitive pressure sensor anchored to the seafloor, which communicates with a surface buoy and satellite. DART detects differences in tsunami waves as small as a centimeter, a level of sensitivity that Bernard says solves the issue of false alarms that plagued past tsunami forecasting technology.
Bernard commends the Kivi Kuaka team’s research. “The only thing I would say is don’t overstress the tsunami warning aspect of this project,” he says, noting that besides the importance of detection, measuring the wave’s size is critical because most tsunamis are harmlessly small, and false alarms cause economic damage and erode public trust.
Jiguet is up front that the idea is uncharted. “I am at a point in my career when I can take such risks,” he says. Even if the attempt to develop a bird-based tsunami early warning system fails, the project will still help scientists protect birds and benefit the French Ministry for the Armed Forces’ mission of aiding climate change and biodiversity initiatives in the Pacific. In that sense, the research has already yielded results. Jiguet says their first season’s tracking data highlights Hawai‘i as an important stepping stone for the birds they tagged—a useful clue for conserving these species amid rising seas and an uncertain future.
hakaimagazine.com, 1 September 2021