Tropical cyclones are synonymous with destruction. But at least one seabird may take advantage of them as feeding opportunities.
The Desertas petrel, a small and threatened seabird native to the North Atlantic Ocean, has long been associated with oncoming storms. A new study suggests that this skilled flier purposely interacts with cyclones, flying long distances toward them and following their wake, researchers report in the July 22 Current Biology.
It’s a risky gambit by the petrel (Pterodroma deserta), which must contend with wind speeds approaching 90 kilometers per hour and swells up to eight meters high. The likely payoff: an abundance of food. The team found markedly higher levels of chlorophyll in the stirred-up, cooler water of the storms’ wakes, suggesting elevated levels of phytoplankton. This could trigger a feeding event that draws the petrels’ prey—fish and cephalopods—to the surface.
Biologist Francesco Ventura and colleagues combined tracking data from GPS units placed on 33 petrels over four breeding seasons with data from cyclone activity during the same time span. These birds’ breeding-related foraging trips are among the longest in the animal world — a rough clockwise circle of about 12,000 kilometers from their colony on Bugio Island, about 450 kilometers north of the Canary Islands, toward Newfoundland and back.
Once the tracked petrels reached about 900 kilometers from the eye of an approaching cyclone, almost one third of them actively flew toward it, the team found. Some 400 kilometers from the eye, the birds slowed down. The GPS data aren’t detailed enough to shed light on their precise behavior, but it appears the petrels may drift on the ocean’s surface, carried by hurricane-force winds through high seas — “conditions that are very difficult to imagine,” says Ventura, of Woods Hole Oceanographic Institution in Massachusetts.
Once a cyclone passed, about half of the tracked petrels followed its wake and nearly a third pursued the storm’s trail for days and thousands of kilometers.
Although “we are still a long way from having conclusive evidence,” Ventura says, he believes Desertas petrels may use infrasound to initially locate cyclones. This very low frequency sound created by wind and waves — called “the voice of the sea” — extends about 900 kilometers from the sound’s source, says Ventura, the same distance at which tracked petrels began to fly toward the cyclones.
Desertas petrels might not be the only species to use hurricane wakes opportunistically, Ventura says. “It’s possible we’re describing a process that triggers a biological response” used by sharks, tuna, turtles and marine mammals for foraging.
Marine ecologist Lesley Thorne says that Ventura’s team has filled “a really important gap” in our understanding of why some seabirds chase storms. Another seabird, the streaked shearwater, flies into and with cyclones — presumably as a way to survive them (SN: 10/17/22).
Linking the large amounts of food in hurricane wakes with seabird behavior “was really, really cool … something that had not been done to date,” says Thorne, of Stony Brook University in New York. It’s the kind of deeper research she believes will help us better understand “how and why wind is impacting seabirds,” particularly as the oceans warm.
