Songbirds ‘talk’ to each other during migration

Every year, the night sky fills with the unseen movement of millions of migrating songbirds, tracing routes carved by evolutionary history. 

While these flight paths are largely guided by innate instincts, new research from the University of Illinois Urbana-Champaign suggests an unexpected social dimension to their nocturnal journeys. 

Evidence from over 18,300 hours of acoustic recordings reveals that songbirds may “talk” to other species as they migrate, potentially sharing information and forming temporary social bonds along the way.

Migration may not be a solitary endeavor

The study, led by Benjamin Van Doren, an assistant professor in the Department of Natural Resources and Environmental Sciences at Illinois, offers a fresh perspective on the traditionally individualistic view of songbird migration. 

The research, initiated at the Cornell Lab of Ornithology, indicates that birds may vocalize during flight to signal their species, age, or sex and perhaps even exchange navigation tips or information about stopover sites.

“We can’t be sure what they’re saying, but birds might broadcast calls during flight to signal their species, age, and sex. And we can certainly speculate that these flight calls could relate to navigation or finding suitable stopover habitat,” Van Doren said.

Earlier studies had documented instances of different species forming temporary partnerships during stopovers. However, this is the first evidence of vocal communication and possible social interactions between songbird species while in flight.

Listening to the night sky

Songbirds migrate primarily at night, making it difficult to observe their movements. To overcome this challenge, Van Doren and his team used acoustic recordings captured at 26 sites in eastern North America over three years. These recordings provided a rare glimpse into the nocturnal world of songbird migration.

“These nocturnal acoustic recordings are really the only window onto this unseen but absolutely massive flow of birds – hundreds of millions aloft over the U.S. on any given night during migration,” Van Doren explained. “It’s something people aren’t usually aware of because it happens when we’re sleeping.”

Analyzing such a vast dataset would have been impractical without recent advancements in artificial intelligence. 

Using machine learning tools, the researchers identified the flight calls of 27 bird species, including 25 well-sampled songbirds, allowing them to detect patterns of co-occurrence.

Social associations in the sky

The team measured how often flight calls from different species occurred within 15, 30, and 60-second intervals. Regardless of the time frame, they found that certain species called in tandem more often than chance would predict.

Further analysis revealed two key factors influencing these associations: wing length and call similarity.

Birds with similar wing sizes were more likely to associate, likely because similar wing lengths correspond to similar flight speeds, making it easier for them to travel together.

Species with comparable vocalizations also showed stronger associations, suggesting that shared calls may facilitate social connections during migration.

Interestingly, species that formed partnerships during stopovers did not maintain those relationships while in flight. Additionally, the birds were not necessarily flying with closely related species or those with similar habitat preferences.

“Species with similar wing sizes were more likely to associate, and wing length is directly linked to flight speed,” Van Doren said. 

“As for vocalizations, it is possible that species’ calls have converged over time because of this social link or that species that happen to give similar calls are simply more likely to gravitate towards each other.”

Expanding our understanding of songbird migration

While the study focused on 25 species, many other nocturnal migrants do not vocalize during flight, leaving much to uncover. 

Van Doren’s team plans to extend their research by equipping individual birds with tiny microphones to track their in-flight “conversations” and interactions with travel companions.

These preliminary findings raise fascinating possibilities. For instance, short-lived species that cannot rely on parental guidance for migration may instead depend on social ties with other birds. 

Conversely, the loss of biodiversity due to climate change and habitat destruction could disrupt these co-migratory relationships, further imperiling vulnerable species.

“This study really calls into question the long-held idea that songbirds migrate alone, solely following their own instincts,” Van Doren said.

Implications for conservation

The discovery of social interactions during migration has significant implications for bird conservation. If certain species rely on social cues or co-migration with specific partners, their survival may depend on maintaining these networks. 

Losses in bird biodiversity could jeopardize these connections, making migration more difficult for some species.

Moreover, understanding the role of social information in migration could help researchers design better strategies to protect migratory birds, particularly as they face mounting risks from habitat loss, climate change, and light pollution.

“Learning more about the consequences of these social connections – not only for migration but also for other aspects of their biology – will be important to inform and manage the risks they face in a changing world,” Van Doren emphasized.

A new perspective on songbird migration

This research challenges the traditional view of songbirds as solitary migrants guided solely by instinct and memory. Instead, it suggests that social interactions and communication play a crucial role in their epic nocturnal journeys. 

As scientists continue to explore these complex dynamics, they may uncover new strategies for safeguarding these remarkable travelers and the ecosystems they connect.

—–

Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.

—–