Bird migrations follow routes that are said to be “in their blood,” that is, born with them, embedded in their genes throughout their evolutionary history. And while that may be true, social learning also plays an important role in the choice of paths to follow.
This is what a team of scientists from the United States and the United Kingdom argue in a article published this week in Current Biology.
Through the analysis of more than 18,300 hours of recordings of songbird vocalizations during nocturnal migratory flights, the investigators suggest that these animals appear to “talk” to one another and even with other species of birds as they move from one place to another.
Previous studies had already pointed to the formation of clusters of several bird species at stopover sites during migrations, but this investigation shows that different species of songbirds form unique groups during migratory flights and communicate vocally with one another.
Although it is not possible to know for sure what these animals say to one another, the researchers believe they may convey information about their species, sex and age, and do not rule out the possibility that they may communicate about flight routes and the location of areas where they can refuel.
“In recent years, there has been a growing recognition of the importance of social information in bird migration, but scientists have mostly documented this in species that travel during the day or in family groups,” says Benjamin van Doren, from the University of Illinois and the first author of the article.
Using artificial intelligence tools to identify the species emitting the recorded sounds, the researchers found that, when in flight, species with similar wing spans and vocalizations are more likely to form flight groups.
In a statement, van Doren suggests that species with similar wing sizes may fly at virtually the same speed, which allows the creation of multi-species groups. Furthermore, those that have similar vocalizations may also communicate more easily with one another, promoting greater social cohesion among different species.
Although still in the realm of speculation, the researchers point out that songbird species that do not live long, and thus may not learn from their parents all the migration routes and the best feeding locations, may turn to social bonds with other species to reach where they need to go.
“This study truly challenges the long-held idea that songbirds migrate on their own, following only their own instincts,” notes van Doren. As the effects of climate change are causing large losses in the world of birds, the researchers fear that these interspecies partnerships, which may be fundamental for the survival of some of them, could be at risk, with potentially disastrous consequences for avian diversity.
“Learning more about the consequences of these social ties—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,” he notes.
