It’s not always the birds of the same feather that flock together. From 18,300 hours of flight calls, scientists have deduced that songbirds communicate and socialize during migration. They “talk” and “buddy up” with other birds during their flight across paths etched in their evolutionary record.
Lead study author Benjamin Van Doren, an assistant professor in the Department of Natural Resources and Environmental Sciences, part of the College of Agricultural, Consumer, and Environmental Sciences at Illinois, says that birds convey information about their sex, age, and species through their flight calls. These calls also aid in navigation and in finding suitable stopover habitats.
Previous research has considered socializing at stopover sites. However, this is the first time scientists have noted how songbirds socialize and build bonds mid-flight through flight calls. Van Doren believes that innate patterning and memory are essential, but it’s also time to examine migratory flights through a social lens.
Social cues during the bird migration have been researched in day flights and family groups. They are usually necessary in birds that form massive aggregations while migrating during the day, like hawks and storks. Young birds learn from elders, but Van Doren suggests that they also learn from birds of other species.
What especially stole the attention of Van Doren is the fact that most of the bird migrations occur at night, when the nights shroud visual cues. To reveal the secrets of migration during the night, Van Doren started looking out for other social cues. Thankfully, he had acoustic samples taken from autumn nocturnal bird migrations from eastern North America. This acoustic record was processed with the help of a machine-learning tool that detected signature flight calls of 27 bird species, including 25 well-sampled songbirds.
After identifying the species, the team checked out how often the calls co-occurred in spans of 15, 30, and 60 seconds. The researchers found stronger-than-expected associations just by chance. The most important factors in this avian affinity were linked to wing length, which directly affects flight speed. Birds with similar flight speeds had similar wing lengths and could remain together during flights. The other factor involves the similarity in the calls of the birds, which, according to Van Doren, have evolutionarily converged through social links.
The research team’s next step is to understand better how these migratory partnerships are built. Their plans involve attaching small microphones to individual birds and recording their flight calls during migration.
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