Migrating Birds Sing to Team Up with Other Species

Migratory birds sing to join other species

Who Gayoung Lee edited by Sarah Lewin Frasier

Small songbirds such as cardinals and warblers migrate thousands of miles, flying at night and resting during the day, to their wintering grounds and unlike many larger birdsthey shun herds and travel separately. But new research suggests they’re not entirely alone in dark skies. Benjamin Van Doren, an ornithologist at the University of Illinois at Urbana-Champaign, and his colleagues set up ground microphones at 26 sites in Eastern North America and collected more than 18,300 hours of bird flight calls. Researchers discovered solitary migratory songbirds they seem to cooperate between species and probably shared information with other solo travelers about who they were and what to see before.

The findings were published on Wednesday Current BiologyThere is increasing evidence that social interactions between species can influence the migratory behavior of songbirds much more than previously thought.

The conventional wisdom was that “every bird follows its own instinct or its own experience,” says Van Doren. “If it’s not a young bird and it’s already (migrated) a few times, they’re certainly relying on memory and experience, but generally they’re doing it on their own.”

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Flying in the dark poses challenges for aerial cooperation, said biologist Allison Pierce, who studies clam migration at the University of Colorado Denver and was not involved in the new paper. For example, visual cues such as the flight path of another bird are missing. This prompted Van Doren and his colleagues to look for other data, or better yet, to listen: seemingly random ping birds chirp every few seconds or minutes.

“It’s not really clear why they spend all that energy and effort calling while they’re migrating,” says Van Doren. “This behavior must have a reason or benefit. Otherwise, they are wasting energy.”

To analyze what turned out to be a huge amount of data, Van Doren and his colleagues used machine learning technology with a customized version of Merlin, a bird call identification application developed by the Cornell Lab of Ornithology.

Individual birds of different species were flying next to each other and calling each other using certain patterns, “more than we could explain by chance,” says Van Doren. So it seemed there was a reason the birds were nearby. The new research “potentially suggests that these birds aren’t just trying to find their way from Chicago to Argentina on their own… and that perhaps there’s a social information being exchanged between the billions of songbirds that migrate at night, completely revolutionizing our understanding of how songbird migration works.” “.

It’s not yet clear what information the birds can communicate, Van Doren says. But the researchers have very good ideas. For example, different species of birds have different calls, but even within the same species, their “pings” vary by age or sex group, so birds can use this information to introduce themselves. Either way, it’s likely that “being in contact with other people can help them … navigate more effectively,” Van Doren explains. They may be exchanging knowledge about landing sites and difficult weather conditions (such as fog or rain), for example. “Migration is a very dangerous time, even for birds that have done it before.”

Researchers have previously observed that songbirds form “mixed-species flocks” as they search for food and avoid predators during the day, Van Doren added. The new study suggests that such partnerships may play a more significant role than researchers thought. Additional research will further test these hypotheses using more direct tracking methods, such as tagging specific birds for tracking during migration.

“If we were to take this large population level and try to understand what the individual is doing,” says Pierce, “it’s going to be key to understanding how the birds are migrating.”

“To me, it speaks to the amazing complexity of how nature works,” says Van Doren, “and it’s exciting to learn new things about these familiar phenomena that are still spectacular.”