Scientists Can Now Track How High Songbirds Fly Over the Ocean—a Potential Lifesaver

Swarmed by mosquitoes and carrying 10-foot metal poles, biologists Erik Johnson and Olivia Butler splash through a swampy nature preserve in Lafayette, Louisiana, on a mission. A concert of bird calls rings out, but the Audubon Delta scientists listen for one in particular: a clear, high-pitched sweet, sweet, sweet, sweet—the tune of the bright yellow Prothonotary Warbler, or “swamp canary” as they’re nicknamed in Louisiana.

Stopping near a nest box, Johnson stretches a net across the poles while Butler places a yellow rubber duck—the perfect color and size to act as a decoy—nearby. She then plays a variety of warbler calls on a speaker, trying to lure a bird. For 15 minutes, flashes of yellow swoop from branch to branch—until finally, one flies into the net. “Yes!” Butler whispers. “Sometimes it takes just mixing it up enough,” Johnson says. The pair catalogue everything—the bird’s wingspan, the length of its legs, and even take a sample of poop—and then affix what looks like a tiny backpack between its wings. Delicately adjusting the “straps” using a crochet needle and a popsicle stick, Butler wiggles the geolocator into place. 

The tag will help the scientists follow the warbler on its migration across the Gulf of Mexico to Colombia and back again next year. Although Lafayette is about 25 miles from the ocean, the team hopes the data—from this bird and many others—will help guide the future of offshore wind development and keep migratory birds safe during long-haul flights. That’s because these devices can do something that other tracking technology cannot: measure how high the small land birds fly across long stretches of water.

When it comes to preventing collisions with offshore wind turbines, avian flight height is a big deal, Johnson says. Today’s turbines can be built to reach more than 900 feet above the sea surface. If songbirds stay well above these heights, then collisions wouldn’t be a threat, he says: “But if they come lower into the atmosphere...that could put them at risk.” While no turbines operate in the Gulf of Mexico today, the Biden administration held the first federal offshore wind lease auction there in 2023 and had planned others. Louisiana has also considered two projects in state waters, closer to shore.

Reducing avian risks posed by wind energy projects is a priority for conservation advocates, says Bill DeLuca, Audubon’s director of migration science. Though they’re not a leading cause of bird deaths (and fossil fuel infrastructure kills far more birds overall), turbine collisions can harm species that are already in decline, he says. On the other hand, renewable energy deployment is urgently needed to reduce fossil fuel use and help stave off the worst effects of climate change, which poses existential risk to both birds and people. In the United States, offshore wind projects are a key part of that puzzle, a 2025 Audubon report found.

Offshore wind farms can negatively affect birds in several ways: displacing them from habitat, reducing food availability in the marine ecosystem, and, most acutely, causing collisions. The federal government’s extensive vetting of wind sites before leasing helps alleviate these risks (though Louisiana’s siting process for state projects has, thus far, been less environmentally rigorous). Operators can also act to minimize harm after farms are built—by outfitting structures with flashing lights to deter birds or turning off turbines during high collision-risk times,  for example. These strategies, however, require data about where and when different birds fly over water.

That’s where the tracking devices come in. Typically geolocator tags that are lightweight enough to use on small species like a Prothonotary Warbler—a bird that weighs less than five pennies do—sense changes in ambient sunlight to gauge its approximate path. But they can’t measure its height. The new tags measure barometric air pressure. Combined with other data, the technology allows scientists to pinpoint both the warbler’s flight path and altitude.  

Since the project began in 2024, Johnson and research partners in Louisiana, Kansas, and other breeding areas have tagged Prothonotary Warblers, Swainson’s Warblers, and Purple Martins that all migrate across the Gulf. Much of the time, he suspects, these birds fly higher than today’s tallest turbines would reach—but may sometimes drop down if they hit storms. With enough data, he hopes to predict when songbirds are more likely to fly at lower altitudes. “If we can model the relationship between flight height and weather patterns, then we can inform the operation of wind turbines and inform risk mitigation measures that are needed,” says Johnson, who is now an assistant professor of wildlife management at the University of Louisiana. 

About 1,800 miles northeast of Lafayette, DeLuca is also partnering with the Vermont Center for Ecostudies on a similar project, focused on Swainson’s Thrushes and Blackpoll Warblers. The latter species flies for three straight days over the Atlantic Ocean as it migrates from North America’s boreal forest to South America. Collecting more precise information about the bird’s journey could likewise inform energy planning in the waters off the East Coast, especially in the Gulf of Maine, DeLuca says. While he’s studied Blackpolls for a decade, this is the first time he’s been able to gather data about the relationship between the birds and offshore wind development. “Up to this point, it was a bit of a guess,” he says. 

Whether more offshore wind turbines will be built is an open question: The immediate prospects for development in the United States are shaky. Although the Biden administration sought to advance this form of renewable energy, President Trump paused federal offshore wind permitting in January upon taking office. This move alone delayed almost 30 gigawatts of planned development, says Katharine Kollins, president of the Southeastern Wind Coalition—or roughly 100 times more capacity than is currently operating. Then, this summer, Congress repealed wind energy tax credits, and the Interior Department rescinded wind energy areas that had been designated as suitable for offshore development. A handful of projects have also been canceled due to supply chain issues and rising costs. 

Although the industry faces undeniable headwinds, Kollins says that it isn’t dead yet: “This is a $25 billion investment in U.S. manufacturing, U.S. supply chain, and U.S. energy infrastructure. And that’s not the kind of thing that you can easily give up.”

And whatever happens, scientists expect their research to provide value that goes well beyond energy planning. “Migration in general is the most dangerous time of year for migratory birds,” DeLuca says. “We know it’s when they’re pushing their bodies to the brink. We know they’re super vulnerable.” That data they’re collecting may offer insights into other causes of species decline, such as loss of stopover habitat.

Back in Louisiana, Butler releases the warbler she’s tagged. Next April, she’ll return to find it again and download the data it carries. That way, she’ll be able to see—more clearly than ever—the contours of this resilient bird’s 5,000-mile roundtrip journey.

This story ran in the Fall 2025 issue as “New Heights.” To receive our print magazine, become a member by making a donation today.