Now, a study from the Max Planck Institute of Animal Behavior in Konstanz, Germany, has an explanation for how this collective phenomenon forms: the storks are choosing to fly together. With data on lifetime migrations of 158 storks, the study provides the first evidence of the social preference of storks during migration. In a paper, appearing in Current Biology, the researchers show that storks chose routes that were heavily trafficked by other storks. Yet, young storks tuned their routes to social hot-spots more than adults did. "It's exciting to see the first clues that storks are actually choosing to fly with others," says Hester Brønnvik, a doctoral student at the Max Planck Institute of Animal Behavior and first author on the study. "But as they gain migration experience, they also gain the independence to ignore social influences." The results have unlocked the first answers to an old question about the world's most iconic migrant. "We can all see that storks fly in flocks, but this observation alone never told us whether or not storks are choosing the routes they take in order to migrate with others," says Brønnvik. "It could be that storks are selecting their routes based on other criteria—like good winds or a particular destination—that happen to put them in the same place." To disentangle the underlying social preference of migrating storks, scientists had to find a way of asking them: why did you choose to fly where you did? Studying route selection The team tapped a 10-year data set that provided the precise GPS locations of 158 storks from southern Germany every hour over their lifetime. "We could see the complete migrations that these storks took every year for their entire lives, from a three-month-old juvenile on its first migration to a highly experienced nine-year old taking one of its last flights," says Brønnvik. Next, the researchers pieced together a... |