The thousands of hours of recordings were processed by a machine learning tool that allowed the research team to detect 27 species\u2019 signature flight calls, including 25 well-sampled songbirds.<\/p>\n
The team first identified species, then measured the frequency with which certain calls co-occurred, testing at intervals of 15 seconds, half a minute and one minute. They found associations that were stronger than would be expected by chance, regardless of the time elapsed.<\/p>\n
Searching for an explanation of the associations, the researchers found that the similarity of calls and wing lengths of species were most important. By contrast, birds who \u201cbuddy up\u201d during migration stopovers were not maintaining the same relationships while flying, nor were they necessarily in the air with closely related birds or species who shared their specific habitat preferences.<\/p>\n
\u201cSpecies with similar wing sizes were more likely to associate, and wing length is directly linked to flight speed. If you imagine two species flying at similar speeds because they have similar wings, then it\u2019s much easier for them to stick together,\u201d Van Doren explained. \u201cAs for vocalizations, it is possible that species\u2019 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.\u201d<\/p>\n
Van Doren noted that 25 individuals was a small representative subset of songbird species who migrate at night, some of whom don\u2019t vocalize during flight. Van Doren and his team have plans to conduct more research, including tracking individual birds\u2019 \u201cconversations\u201d with flight partners by attaching tiny microphones to be worn throughout their migrations.<\/p>\n
The preliminary results bring up many speculative theories, such as that short-lived songbird species who aren\u2019t able to rely on their parents for guidance might rely on social ties during the journey. In addition, the rapid loss of bird biodiversity due to habitat destruction and climate change may jeopardize co-migrating partner species.<\/p>\n
\u201cThis study really calls into question the long-held idea that songbirds migrate alone, solely following their own instincts,\u201d Van Doren said. \u201cLearning more about the consequences of these social connections \u2014 not only for migration, but also for other aspects of their biology \u2014 will be important to inform and manage the risks they face in a changing world.\u201d<\/p>\n