Near the tip of northern Colombia, snow-capped mountains and steep, emerald hills rise above the Caribbean Sea. The Sierra Nevada de Santa Marta is a paradise, especially for dozens of endemic birds. The balmy, lush landscape also beckons spring migrants such as Gray-cheeked Thrushes, which fly in from their far-south wintering grounds to fill up on berries and bugs.
Fueling stations like this provide vital energy for birds as they embark on long flights toward their breeding grounds. But while some species take multiple breaks over the course of the journey, the six-inch thrush can travel non-stop between the Americas. The Colombian layover is enough to power it over thousands of miles, allowing it to reach the northern hemisphere in record time—as fast as three days to Canada, a recent study in Scientific Reports finds.
“It was commonly believed that migratory birds needed more time and energy for their journey and would require several stops along the way to refuel,” says Camila Gómez, a Ph.D. student at the Universidad de Los Andes in Colombia and lead author on the paper. “But then we saw a breakthrough with the thrushes.”
In spring of 2015, Gómez led a team from institutions in Colombia, Canada, and the United States to the Santa Marta mountain range to tag and track 133 Gray-cheeked Thrushes. Using teeny radio transmitters and the Motus Wildlife Tracking System, the researchers were able to follow the birds in real time during their odyssey. In just a few days they had their first big reveal: One little thrush was able to complete the 2,000-mile trip in the span of a long weekend. Over the course of the season and again in spring of 2016, Motus towers pinged back more thrush locations in the Gulf Coast, Indiana, and Ontario. The team gauged that the length of migration ranged between three to forty days.
“To be able to save on time, these birds are doubling their body weight,” says Ken Rosenberg, co-author and an applied conservation scientist at the Cornell Lab of Ornithology. Fruits and insects help them store extra fat, which is often depleted by the end of the migration. But the thrushes further capitalize on the riches in Santa Marta and pack on extra flab, so they’re in good mating shape when they get to their destination.
On average, the birds remained at Santa Marta for nearly two weeks. Those that didn’t take their sweet time at the stopover, or didn’t feast enough, took up to 30 days longer to migrate than their plumper counterparts. This could have detrimental effects: Longer transits means higher risks of exhaustion and lower chances of making it to their breeding grounds on time. “Even when birds fly in from their Amazonian wintering grounds to Santa Marta, we noticed they’re not in good condition in some years. Some thrushes were thinner and had less fat, so that means they’ve used almost all their energy to get here,” explains Nick Bayly, co-author of the study and Migratory Species Manager at SELVA, a Colombian nonprofit.
By understanding how migratory birds rely on this valuable stopover site, the research team was able to project how changes to the region might affect traveling birds. The Gray-cheeked Thrush may already be facing pressures up north, due to climate change and logging in the boreal forest. Any setbacks in their migration grounds could sap the population even more. Though the Santa Marta mountains are protected as a national park, small coffee growers are springing up around the site, threatening surrounding rainforests and river valleys. Most of these farmers, however, see the need to conserve the area and are aiming to silmultaneously “produce and protect.”
As the Colombian government and small businesses endeavor to preserve the thrushes’ habitat, Gómez and her team are expanding their research into a long-term study called the Neotropical Flyways Project. The goal is to highlight the importance of habitat conservation for migratory birds, identify other major stopovers, and track various species in regions of Colombia, Costa Rica, Panama, Honduras, and Nicaragua. “This way we will cover the major flyways and understand which birds use what regions and habitats during one of the most critical phases of their annual cycles,” Gómez says. She notes that both scientists and community members are eager to help all visiting birds succeed in migration.
Correction: The story previously stated that the tracked Gray-cheeked Thrushes were flying non-stop to their breeding grounds. But the study only showed that they were traveling continuously to various spots in North America before heading on to their final spring destinations.
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