Scientists can predict which storks will migrate to Africa in autumn and which will remain in Europe

For little Louis, it is the most exciting day of his life: just six or seven weeks ago, the young stork came into the world on a birch tree in Radolfzell on Lake Constance. Up to this day in June 2014, he has only known his parents and three siblings. But suddenly strange beings have appeared at the nest and are holding the four small white storks captive. They are Andrea Flack and Wolfgang Fiedler of the Max Planck Institute for Ornithology and the University of Konstanz. In the coming years, the scientists will learn from Louis and other young storks that, on their migrations south, storks follow other storks who are particularly good at exploiting thermals, allowing them to flap their wings as little as possible as they fly. The efficient fliers migrate to West Africa, while the others spend the winter in southern Europe. From their data, the researchers can tell which storks will fly where just ten minutes after the birds take off. For days, Andrea Flack and Wolfgang Fiedler have been visiting storks' nests on the western shore of Lake Constance. The aerial ladder of the fire brigade raises them to the stork nests at lofty heights so that they can strap small tracking devices onto the backs of the nestlings. The aim is to follow Louis and 60 other young storks on their migration. The instruments, which weigh less than 60 grams, record the GPS coordinates of the birds' location. They also measure the animals' movements using accelometers. This allows the researchers to determine whether and, if so, how the birds are moving. For Louis and his nest mates, the harmless procedure is over in just a few minutes. Fully engaged in perfecting their flying skills, it is likely that they very soon forget the strange encounter with the scientists. For the researchers, however, the work has only just begun. From now on, they will collect and evaluate huge volumes of data, because the tracking devices log the storks' GPS coordinates every second for two to five minutes every 15 minutes, and this for weeks. Once a day, the devices send a text message containing the location and movement data via the local mobile network, just like a mobile phone. The data then flow automatically into an online database called Movebank, a free-to-use online platform developed by researchers led by Martin Wikelski, which allows scientists to log animal migrations anywhere in the world. Because the storks around Lake Constance fly all the way to West Africa for the winter, the mobile network costs would be enormous, given the immense volumes data involved. Andrea Flack therefore follows the birds by car all the way down to Barcelona to download the data once a day using a base station. In Africa, the devices log data at longer intervals to reduce the amount of data generated. A mobile phone for storks Louis, too, was fitted with his "mobile phone" on that day four years ago. As it turned out, he was the first among his nest mates to travel south. He joined a group of 27 other tagged storks. After five days of flying, 17 of them were still together. Louis first skirted the Alps past Bern towards Lake Geneva and crossed the Rhone south of Lyon. On the evening of 23 August, he reached Montpellier on the French Mediterranean coast and then on the following day flew along the coast towards Spain. He crossed the Pyrenees and spent several weeks on a landfill site a hundred kilometres northwest of Barcelona. He then flew to an area around Madrid and spent the winter there at a landfill. He remained in Spain until the spring of 2016 and returned to Germany in March 2016.