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When Hurricane Irma was barreling up the Atlantic coast of the United States in 2017, Bradley Wilkinson was at Clemson University in South Carolina where he had just started his doctorate studying brown pelicans. As people fled the storm’s path, he realized the GPS trackers on 18 pelicans—intended to measure where they found food—might be able to answer a different question: what would the birds do to survive the storm?
Studying how birds behave during hurricanes is a tricky task. Usually the aftermath of the storm draws the most attention, like how 2017’s Hurricane Maria killed half of Puerto Rico’s namesake parrots. Or how birds end up hundreds of kilometers off course or away from home. But advances in technology, including miniature GPS trackers, have made it possible to study animal behavior during these storms “without risking the life of the researcher, which is huge,” says Wilkinson.
During three hurricanes—Irma in 2017, and Florence and Michael in 2018—Wilkinson used the GPS tags to learn how the pelicans behaved.
He found that during low air pressure and high winds—when the storms were strongest—the birds took refuge in estuaries, or hid behind barrier islands and highway overpasses close to their breeding colonies near Charleston, South Carolina. Hunkering down cost the birds a few days of foraging, but seemed to be a fine-tuned survival technique—the only evidence that a bird might have died was when one GPS tracker went silent during Hurricane Florence.
Kyle Horton, an ornithologist from Colorado State University who was not involved in the study, says that birds have two main strategies to survive a hurricane: they can find some way to weather the storm, or avoid it.
Previous studies suggest some birds, like sparrows, can sense changes in barometric pressure and adjust their behavior, says Patrick Jodice, a wildlife biologist at Clemson University and coauthor of the new study. This gives birds time to seek shelter ahead of damaging winds.
In other cases, weather radar shows birds trapped in the storm’s eye, possibly a safer place to avoid the dangerous hurricane winds. And frigatebirds, pelagic birds related to pelicans, fly to higher altitudes when close to the eye of the storm, presumably to sail through the storm faster.
Horton says the pelicans seem to be relying on both strategies. The pelicans weathered the storm by staying put close to their summer breeding sites along the South Carolina coast, but they also moved behind barrier islands to hide and avoid the storm. An alternative strategy—flying hundreds of kilometers to avoid a storm—could waste a lot of energy.
What remains unclear is how hurricanes affect pelicans over a longer term. Alexandria Hounshell, a biogeochemist who was not involved with the study, says that rain from hurricanes can flush sediment and extra nutrients into estuaries. These pulses might make it harder for birds to find food in a storm’s wake. “That would be an interesting thing to explore … how does this manifest up the food web and ultimately to foraging behavior of birds?” says Hounshell.
Scientists may need to wait to find answers to this and other questions. It’s rare to have GPS-tagged birds in places about to be hit by large storms says Horton, which makes this new study even more valuable.