May 12 (UPI) -- When researchers mapped the paths of sooty terns and hurricanes in the Atlantic, they found overlapping paths moving in opposite directions.
"That means these birds, who are usually very tired from traveling long distances over water without rest, are flying head-on into some of the strongest winds on the planet," Ryan Huang, a Duke University doctoral student, said in a news release.
The study -- published in the journal PeerJ -- is the first to compare the seabirds' annual migratory path to the trajectory of hurricanes.
The correlation isn't just academic, it yields unfortunate results. Researchers mapped the location of banded sooty terns later found dead. When they compared the map with historic hurricane data, they found a strong correlation between storm systems and dead seabirds.
"What's really interesting is that it's not just the big category 4 and 5 storms that can kill large numbers of birds," said Stuart L. Pimm, a professor of conservation ecology at Duke. "A series of smaller, weaker storms may have the same impact as that of a single large, strong storm."
Sooty terns breed in the Dry Tortugas in the Florida Keys. Each summer and fall they migrate east and west across the Caribbean before heading south to their wintering grounds in South America.
If global warming results in an uptick in the frequency of large storm systems and extreme weather, sooty terns could face greater adversity on the annual migration.
The species isn't endangered but it's long been used an indicator species for the health tropical ecosystems.
"If there are changes taking place in the ocean, you'll see corresponding changes taking place in the health of these tern populations, among other indicator species," Huang said. "That's what makes our findings somewhat concerning. If these birds are experiencing negative effects from changing ocean conditions, they are unlikely to be the only species affected."