Minnesota corn fields pose migration risk for songbirds, study shows
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Twice a year, billions of songbirds race through Minnesota’s skies, making their journey between the U.S. and South America in search of richer resources and gentler weather.
But for many songbirds, flapping through Minnesota isn’t easy.
In new research from Cornell University, scientists have found that the Corn Belt’s large stretch of farmland forces songbirds to alter their natural flight patterns.
Around 50 percent of the state’s total land area is made up of farmland. For migrating songbirds, these agricultural fields offer little food and practically no shelter. Researchers compare the trek to flying over larger natural barriers like the Gulf of Mexico.
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“Fewer insects means fewer food resources, which is more challenging for birds that rely on them during migration,” said Chad Witko, specialist in Avian Biology at the National Audubon Society, who was not involved in the study. “But as farming becomes more efficient, there’s less waste—so even those resources might be disappearing now.”
During migration, songbirds rely heavily on stopover habitats with dense vegetation, native plants and plenty of insects to rest and refuel. But instead, they’re being met with barren agricultural fields.
“Migration is an extreme thing during the life cycle of a bird. It’s one of the three most intensive things birds do—along with breeding and molting,” Witko said. “They must fatten up. They must fuel up. They must make these journeys.”
When birds are unable to stop along their intended migration path to rest, they face higher risks of exhaustion, starvation and death.
“We lost 28 percent of the entire breeding bird population in North America over the past five decades, and the trend is continuing,” said Fengyi Guo, post-doctoral fellow and the study’s lead author.
Using weather radars to track songbirds across 47 sites, Guo and her team collected data for five years, attempting to see how the songbirds were adapting on their route to South America and back. Weather radar can track bird movements in the sky, especially during migration. They appear on radars as tiny blobs or echoes.
Through their analysis, Guo and her team were able to discover that as songbirds cross the Corn Belt, especially in parts of Minnesota, they fly much faster than over forested regions. To survive the trek across farmland, many songbirds were also forced to adjust their flight timing and altitude to ride favorable tailwinds, helping conserve precious energy.
Her team was also able to find that while some birds did manage to stop along the way, those rest breaks were limited to pockets of forest that were scattered like stepping stones across the state’s rolling plains.
“There’s a lot that goes into agriculture—groundwater management, pesticide use, irrigation—but at the most basic level, the more continuous habitat we lose, the harder it is for birds to thrive,” Witko said.
In Minnesota, agricultural fields help grow some of the state’s most profitable crops like corn and soybeans. Guo and her team say removing farmland may not be an option, but they say more conservation attention is needed to ensure the existing stopover habitats are protected. Researchers say looking to farmland with lower agricultural yield might provide opportunities for bird rest and refueling sites.
Guo and her team are working to create a solution that benefits both farmers and the environment.
“We are currently working with like government agencies like USDA on a new conservation framework called the Eastern Deciduous Forest conservation framework,” Guo said. “The idea is that we’re incentivizing the farmers and private landowners to have more bird friendly practices.”
Guo says that while the sky is still full of birds now, fewer return each year. She hopes that her research will encourage farmers to practice smart land use and turn the Corn Belt from a barrier and into a bridge, one that helps guide songbirds safely to South America and back.
