In 2007, on a beautiful summer day in Austria, a group of northern bald ibises trailed two paraplanes, which were colorful gondolas powered by propellers and carried by parachutes. Although these birds resembled vultures while grounded, their appearance transformed in flight, showcasing their elegantly curved bills and iridescent black wings.

The scientist piloting one of the paraplanes aimed to guide the ibises to an Alpine mountain pass and ultimately to wintering grounds in Tuscany. Historically, these birds were abundant across Europe, nesting in areas now known as Austria, Germany, and Switzerland, until they faced extinction in the early 1600s due to hunting. If this small group of 20 could successfully learn the route to Tuscany and return independently, it would mark the first migration of northern bald ibises in Europe in four centuries.

However, the ibises strayed from their intended path. After following the paraplanes for about five miles, they abruptly turned back to their starting point, landing in a field where they preened and made loud calls. They resembled a disoriented punk band, their black feathers contrasting with their receding red foreheads. “Scheisse,” exclaimed Johannes Fritz, the scientist, in frustration.

For four years, Fritz had embarked on an unprecedented challenge in zoology: teaching an ancient bird species to migrate. As a doctoral student at the Konrad Lorenz Research Station, established by the Austrian zoologist known for his work on imprinting in young birds, Fritz was inspired by the film Fly Away Home, which depicted a girl teaching Canada geese to migrate using a microlight. Despite his experience with hand-raised ibises, he recognized that for these birds to thrive in the wild, they needed to master migration on their own.

By 2007, his hopes were dwindling. Did he possess sufficient knowledge about migration to ensure the project's success? James Gould, a Princeton University ecology professor and co-author of Nature’s Compass, has called animal migration “one of science's greatest mysteries.” At that time, the only known migrating northern bald ibis colony existed in Syria, with little information available about their behavior.

Fritz persisted for six years, leading eight migrations with the ibises. In 2011, a female ibis made history by flying a new migratory route solo, a remarkable feat. These migrations have yielded surprising insights that enhance scientists' understanding of avian navigation, learning, and energy conservation. Martin Wikelski from the Max Planck Institute of Ornithology likened tracking the ibises' flights to tracing human migration from Africa.

During a recent evening at his colony in Burghausen, Germany, Fritz, now 46 and head of the "Waldrappteam" (the German name for the species), shared that he never intended to become a flight instructor for ibises. He had joined the Lorenz station to study social behaviors in greylag geese, only for the northern bald ibis to unexpectedly enter his life. This May, the Waldrappteam received its largest grant yet—over 4 million euros from the European Commission and other sponsors.

By the 1990s, the northern bald ibis was not only extinct in Europe but also critically endangered globally, particularly in the Middle East and North Africa. In the 1950s, Turkey's extensive use of DDT decimated many birds and disrupted their reproduction. In the 1970s and 1980s, conservationists captured over 40 remaining wild birds, preventing their migration while allowing them to breed in captivity. Despite successful breeding, the wild population continued to dwindle and was declared extinct in 1990. Their migration patterns vanished, leaving their descendants in Turkey, raised by humans and unaware of their ancestors' wintering grounds.

Meanwhile, zoos learned to breed northern bald ibises using birds from a North African lineage, resulting in an excess of captive birds. Some conservationists experimented with reintroducing these birds into the wild, but the young birds failed to form cohesive groups and often wandered off.

In 1997, Kurt Kotrschal, who succeeded Lorenz as director of the Lorenz station, acquired birds from the Alpenzoo in Innsbruck, hoping to establish a non-migratory colony through imprinting. Newly hatched chicks were bonded to human caregivers, who provided food and protection. Surprisingly, in August of their first year, nearly all the birds flew away. Reports of sightings came from distant locations, including the Netherlands and Russia.

What drove the birds to abandon their caregivers? One plausible explanation, marking the first key insight into the ibises' migratory behavior, was Zugunruhe: a seasonal migratory restlessness triggered by hormonal changes that compel birds to leave their breeding grounds for warmer areas during winter and return north to breed in spring.

While some birds, like geese, readily abandon migratory traditions when conditions allow, the ibises' unexpected August journeys revealed a powerful drive to migrate, even without knowledge of their destination. This presented a challenge for Kotrschal, who ultimately established a sedentary colony at the station. However, it also opened the door for innovation: if someone could channel the ibises’ restlessness and teach them their migratory path, the lost traditions could be revived.

Enter Fritz, who theorized that migration was a learned social behavior for ibises, akin to geese, cranes, and other waterfowl. These birds tend to follow experienced adults on their inaugural migrations, memorizing visual landmarks along the way. This contrasted with other birds, particularly migratory songbirds, which possess a powerful innate migration instinct, requiring no learning.

Although the ibises had an instinctual migratory drive, their navigational skills were evidently lacking. During their initial year at the station, many birds flew north, following the valley, when they should have headed south for winter. Given their strong inclination toward social learning, Fritz believed it might be relatively straightforward to teach them a new migration path. He devised a plan to have human caregivers pilot two-seat microlights, calling out to the birds to follow them.

In 2001, Fritz secured funding from the Vienna zoo to purchase an older microlight, similar to the one depicted in Fly Away Home, which featured a rigid wing instead of a parachute. He attended a pilot school in Spain, where he quickly learned that flying induced motion sickness. His instructor advised against disclosing this to the doctor, as it could disqualify him. Determined, Fritz managed to keep his queasiness under control and returned home with his pilot's license.

While no historical records indicated where the ibises might have wintered in Europe, Fritz speculated that Tuscany was a suitable location. Consulting with Italian ornithologists, he confirmed that various bird species indeed winter in the renowned Italian wine region. He located a nature preserve along the western coast of Italy, managed by the Italian branch of the World Wildlife Fund, which permitted him to set up an aviary for the birds.

In August 2003, he charted a 680-mile route through the Alps, along the Tagliamento River to the Adriatic Sea, following the coastline and crossing the Apennine mountains to reach the nature preserve. He aimed to guide the birds along prominent landmarks they could remember.

The initial flights proved challenging. The old microlight was too fast for the ibises, with a minimum speed of 37 miles per hour, while the birds could only reach a maximum of 27 miles per hour. Fritz often found himself circling back to wait for them. The more significant issue, however, was that the imprinted ibises frequently refused to fly. “We assumed the birds would follow when we wanted them to,” Fritz reflected. But it soon became evident that the ibises had other plans. Even when they agreed to follow, they often landed prematurely before reaching their intended destination, forcing Fritz to plead with landowners for permission to camp on their properties.

“It was hilarious,” Kotrschal remarked, who accompanied the migration on the ground. “In the morning, you wouldn’t know where you would end up in the evening. Sometimes it was a field in northern Italy, and once it was the first international airport of Venice.” Fritz, however, found little humor in the situation, as his lack of knowledge about the ibis' natural migration became evident.

That year, the birds' longest flight spanned approximately 19 miles—a modest success. The team resorted to transporting the birds by van for various segments when they resisted flying. Nevertheless, the birds eventually reached Tuscany, albeit in small increments. Subsequent years showed improvement as Fritz acquired slower microlights and allowed for longer rest periods. Yet, traversing the Alps remained a significant hurdle; he never managed to cross the range without transporting the birds partway in a van. By 2007, he abandoned the Alpine route, concluding that the ibises were simply unable to navigate the mountains.

Fritz began to doubt his piloting skills and enlisted Walter Holzmüller, an Austrian paraplane champion, as a co-pilot. Holzmüller introduced new, slower paraplanes, which proved more suitable for the birds' pace. Fritz hoped that this new route, which bypassed the Alps by traveling east through Slovenia, would be more effective.

These adjustments ultimately yielded positive results. The human-led migration began to gain momentum. Holzmüller observed that the birds would lose interest if he flew in a straight line, prompting him to weave to maintain their engagement. Yet, what the ibises truly craved was to soar in thermals. Research indicated that large birds like storks and vultures conserve energy by spiraling upward in warm air currents and gliding down to the next one. No one had previously taught the ibises that this soaring technique would be the most efficient way to migrate. Wikelski noted that the hand-raised birds retained the ability to utilize thermals and conserve energy effectively.

This new approach enabled both the paraplanes and the birds to travel for extended periods. On a summer day in 2010, the birds flew for nearly six hours and covered over 160 miles, comparable to the distances observed in the Syrian population. “It was by far the longest flight of an airplane accompanied by hand-raised birds,” Fritz later boasted in a press release. Fourteen birds arrived in Tuscany within just seven flight days, enjoying a bountiful winter of foraging among the fields.

In July 2011, Fritz celebrated a long-anticipated success: a lone ibis named Goja returned independently from Tuscany to the breeding grounds in Burghausen. Soon after, other birds followed suit. GPS trackers on the birds indicated that they had taken shortcuts directly over the Alps.

The ibises defied Fritz's assumption that they would adhere to the route he had taught them, navigating instead via completely new— and more efficient—paths through areas they had never previously encountered. It appeared that all Fritz needed to do was direct them to the wintering site, as “everything else is in their genetic background,” he explained.

Fritz shared his findings with fellow researchers, who expressed astonishment. “We know other animals exhibit similar behavior on a small scale,” Wikelski remarked. “Desert ants can take a curvy path, and when they decide to return, they go straight back.” However, Fritz's birds represented the first observed natural vertebrate population demonstrating this capability. Gould affirmed that the ibises' migration was “certainly groundbreaking,” indicating their sophisticated navigation skills and suggesting similarities to migratory birds without social learning.

By closely tracking each member of this newly migrating population, Fritz recognized that Goja, the pioneering bird, did not learn her shortcut from others but rather devised it independently. She subsequently taught her offspring, leading a young male bird directly south to the wintering grounds. Fritz had successfully reconnected the ancient ibis with its migratory instincts. In 2012, Goja produced offspring, leading Fritz to exclaim, “Goja is essentially the first breeding migratory bald ibis in Europe in almost 400 years. This is a significant success, demonstrating that we can give this bird a second chance in Europe and facilitate its return to the wild.”

Nevertheless, the ibis remains vulnerable to threats beyond its control. Tragically, during one of her migrations last year, Goja was shot and killed by hunters in Tuscany. Fritz's team estimates that up to 49 out of the 102 ibises they guided to Tuscany have fallen victim to illegal hunting. The latest European Commission grant includes funding for an anti-hunting initiative aimed at combating this issue.

On a warm May day, with the air electric after a recent storm, Fritz visited the Burghausen colony to check on the ibises. Atop a two-story aviary, seven nests housed parents tending to their eggs. Initially, the birds had quarreled at the start of the breeding season, stealing nesting materials and engaging in squabbles, but they now appeared unusually calm.

Fritz took pride in the fact that the ibises were contributing to scientific understanding of migration. Franz Bairlein, director of the Institute of Avian Research in Germany, was studying the birds to gain insights into long-distance migration and how birds swiftly switch between two opposing physiological states: high energy expenditure during flight and energy storage during stopovers. By analyzing blood samples collected daily before takeoff and after landing, Bairlein aimed to correlate the ibises' blood chemistry with their flight behavior, a groundbreaking endeavor. Another research group focused on the aerodynamics of the ibises during flight, examining how their V formation provided clues into energy conservation during long migrations by drafting and reducing air resistance.

The outcomes of these studies could equip Fritz with valuable data, enabling him to enhance his leadership during future human-led migrations in 2014, with the goal of increasing the sustainable migratory population in Europe. He plans to attempt passage through the Alps again, but this time, he will follow routes that the birds have independently chosen. He also hopes to uncover the physiological reasons behind the birds' frequent need for rest, a challenge that has persisted since the very first migration. “They have ample food and maintain a healthy body weight, yet at times they simply refuse to continue,” he noted. “This remains a mystery.”

This year, seven new chicks hatched at the Burghausen colony. With a grin, Fritz predicted that in five years, Europe could host over 100 “free, wild” northern bald ibises, breeding north of the Alps and migrating south for the winter.

Chelsea Wald is a freelance science writer contributing to Science and New Scientist. She frequently migrates between the United States and Austria.

Originally published at Nautilus on December 18, 2014.