Leaning out of an ultralight aircraft, Corinna Esterer turns toward a flock of peculiar black birds soaring just a few metres away. “Come, come ibis,” she yells through her megaphone. Drawn by Esterer’s voice, the birds dart to the aircraft, and follow it to a field overlooking Lake Constance in southern Germany. Once on the ground, the ibis flock to Esterer. To the birds, the young woman is their parent.
For more than 300 years, the northern bald ibis has been extinct in the wild in central Europe, with small populations surviving only in zoos. But recently, it has celebrated a slow but steady comeback thanks to human foster parents who have shown the birds how to migrate south by leading the way in ultralight aircraft.
This year is the fifth time the team has taken young birds that hatched in captivity on a three-week migration across the Alps to their wintering grounds in Tuscany.
“It really is pioneering, the first [example] of its kind in which we have reintroduced a bird species with the help of human-led migration,” said Johannes Fritz, the head of the project. Fritz has spent most of his career trying to bring the ibis back. “Granted, they are not very beautiful, but [they are] charismatic,” he said.
More than 100 individuals now live independently in southern Germany and Austria. The first generations have already bred in the wild, and taught their offspring the same migratory path they learned from their human parents.
Preparations for this year’s migration started when the foster parents took in 31 chicks at the Vienna zoo when they were just a few days old. They were fed 10 times a day and began to recognise the women feeding them as parents, before they were taken to their training camp at Lake Constance several weeks later.
Fritz said he drew inspiration from the 1996 film Fly Away Home in which one character, Amy, flies an ultralight aircraft to show a flock of orphaned geese their migratory path. At the time of the movie’s release, Fritz was working on his PhD at a behavioural science research institute that had started to work with northern bald ibis chicks born in a zoo.
Despite having only survived in zoos for centuries the young birds’ instinct to migrate kicked in, and in August they tried to fly south. But without an elder bird to guide them, they died along the way. “When we saw the movie, we joked that we could do what Amy was doing with the geese,” Fritz said.
Following a feasibility study that took 10 years, the project received more than €4m (about half of it from the EU) to establish a viable population in the wild. That critical point has been reached, Fritz said, but the benefits go beyond just the reintroduction of the birds. Using GPS trackers on the birds’ backs, the team has managed to better understand how migratory birds save energy by flying in their typical V-formation.
Research is also under way to understand when and how the ibis decided to swap positions within the V-formation. And in the future, human-led migration might have to help with the reintroduction of other migratory birds, which are under threat worldwide mostly due to loss of habitat, but also because of collisions with glass buildings, electric poles and wires.
For now, however, the main worry is getting the birds to follow the aircraft. While they have a strong bond with their “mothers” and follow them around on the ground, flying is more difficult, Fritz said.
On a recent afternoon, only half of the flock followed the aircraft, while the other half was so confused that they simply returned to their aviary looking for their parent.
“They don’t totally get yet when their parents are sitting in there,” Fritz said as he pushed the aircraft – essentially a metal cage with two small seats, a propeller and a parachute – back into a small shelter. “But one day, just like that, it clicks. And then, we can take them to Tuscany.”
