Songbirds benefit from social networks during migration

Migration is a natural and adaptive phenomenon, often prompted by seasonal changes, that plays a crucial role in maintaining ecosystem health. Animals, including birds, may travel vast distances, sometimes covering thousands of miles, in search of food, better living conditions, or to find a mate. 

While human migration is typically driven by economic or social factors, it is less common and often involves complex motivations. But what if animal migration, particularly bird migration, also included a social component?

Joely DeSimone is a postdoctoral research scientist with the Animal Migration Research Group at the University of Maryland Center for Environmental Science (UMCES) Appalachian Laboratory.

Social relationships of songbirds

DeSimone collaborated with Emily Cohen, an associate professor at UMCES, and four North American bird observatories on a study funded by the U.S. National Science Foundation (NSF). The research revealed consistent social relationships among different species of songbirds during migration.

“Global migrations of diverse animal species often converge along the same routes, bringing together seasonal assemblages of animals that may compete, prey on each other, and share information or pathogens,” wrote the study authors. 

“These interspecific interactions, when energetic demands are high and the time to complete journeys is short, may influence survival, migratory success, stopover ecology, and migratory routes.”

Social interactions during migration

Although it is challenging to study interactions among animals that migrate together, the findings of this analysis suggest that interspecies relationships play a significant role in shaping the ecology of animal migration. 

While the co-occurrence of different species during migration is generally thought to be influenced by their preferred habitats and the timing of their movements, this study shows that these interactions are also shaped by consistent social relationships between species.

Meaningful social ties among songbirds

According to DeSimone, the team found evidence of meaningful social relationships among migrating songbirds that have generally been thought to undertake solitary, independent journeys,” said DeSimone. 

“Interactions among these animals – like harmful competition for food or beneficial information sharing about habitat and predators – could affect the success of their migrations,” said DeSimone.

“Interestingly, we found the species relationships to be largely positive, suggesting they don’t avoid each other and may actually benefit from social interactions during migration.”

Long-term data on migratory movements 

Bird banding stations, such as those that contributed data to this study, capture thousands of birds as they stop to rest and refuel between migratory flights each spring and fall. 

These stations gather extensive long-term data on the migratory movements of various bird species. The research team identified species relationships by applying social network analysis to over half a million banding records from 50 bird species collected over two decades.

“We found support for communities on the move – considering migrating birds as part of interacting communities rather than random gatherings of independently migrating species,” Cohen said. “This work could change the way we study and conserve animal migrations.”

Broader implications of the study

Human activities and climate change are posing significant threats to animal migrations worldwide. Migratory animals are in decline globally, and the timing of their movements is shifting. 

DeSimone and Cohen suggest that species-specific processes might have far-reaching impacts on entire migrating communities in ways that have not yet been fully explored.

“Learning that migrating birds are characterized by persistent, non-random assemblages of interacting species opens the door to myriad questions at the intersection between networks, migration, and the environment,” said Steve Dudgeon, a program director at the NSF. 

“Further research can help answer whether successful migrations depend on these networks, if some relationships are more important than others to migration, and whether key links in these networks are more vulnerable to environmental changes en route.”

This study, published in the Proceedings of the National Academy of Sciences, could pave the way for a new field of research – the community ecology of migration – with the aim of fostering future investigations into the nature and implications of species interactions among migrating animals.

“Our findings support an understanding of animal migrations that consist of networked communities rather than random assemblages of independently migrating species, encouraging future studies of the nature and consequences of co-migrant interactions,” the authors concluded.

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