After Binging in Colombia, Thrushes Can Fly Non-Stop to Canada in Mere Days

Taking multiple refueling breaks helps some birds fare better during migration. But for Gray-cheeked thrushes, a two-week binge session in Colombia can be all they need to reach North America.

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听landscape also beckons spring migrants such as听Gray-cheeked Thrushes, which fly in听from their far-south wintering grounds to听fill up on berries and bugs.听

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,听the six-inch thrush听can travel听non-stop between the Americas.听The Colombian layover is enough to power it over thousands of miles, allowing it to reach the northern hemisphere听in record time鈥攁s fast as three days to Canada, a recent study in听finds.

鈥淚t was commonly believed that migratory birds needed more time and energy for their journey and would require several stops along the way to refuel,鈥 says Camila G贸mez, a Ph.D. student at the Universidad de Los Andes in Colombia and lead author on the paper. 鈥淏ut then we saw a breakthrough with the thrushes.鈥

In spring of 2015, G贸mez 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 , the researchers were able to follow the birds in real time during their odyssey. In just a few days听they had their first big reveal:听One little thrush was able to complete听the 2,000-mile听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听three to forty days.

鈥淭o be able to save on time, these birds are doubling their body weight,鈥 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听capitalize on the riches in Santa Marta听and pack on extra flab, so they鈥檙e 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鈥檛 take their sweet time at the stopover,听or didn鈥檛 feast enough, took up to 30 days longer to migrate than their plumper counterparts. This could have听detrimental effects:听Longer transits听means higher risks of exhaustion and lower chances of making it to their breeding grounds on time. 鈥淓ven when birds fly in from their Amazonian wintering grounds to Santa Marta, we noticed they鈥檙e not in good condition in some years. Some thrushes were thinner and had less fat, so that means they鈥檝e used almost all their energy to get here,鈥 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听site, the research team was able to project how听changes to the region听might affect traveling birds. The Gray-cheeked Thrush may already be facing pressures up north, and logging in the boreal forest.听Any setbacks in their migration听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 鈥減roduce and protect.鈥

As the Colombian government and small businesses听endeavor to preserve the thrushes鈥 habitat, G贸mez and her team are expanding their research into a long-term study called the . The goal is to highlight the importance of habitat conservation for migratory birds, identify other major stopovers, and track听various species in regions of Colombia, Costa Rica, Panama, Honduras, and Nicaragua. 鈥淭his 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,鈥 G贸mez says. She notes that both scientists and community members are eager to help听all听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听study only showed that they were traveling continuously to various spots in North America听before heading on to their final spring destinations.

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