Since 2004, the Waldrappteam has been guiding juvenile Northern Bald Ibises, hand-raised by human caregivers, from their breeding grounds north of the Alps to suitable wintering sites using ultralight aircraft. In addition to the migration route to the original wintering site at Laguna di Orbetello in Italy, a second route has been established since 2023, leading to the wintering site in Vejer de la Frontera.
This method, currently applied exclusively by the Waldrappteam, has been continuously optimized over the past 20 years. Daily flight stages initially covered about 60 kilometers; today, the birds can fly up to 300 kilometers per day. The number of birds released per season has increased from only a few individuals to up to 36.
These optimizations were made possible primarily through the further development of rearing methods, adaptations of the aircraft, and accompanying research on flight techniques and flight efficiency of the Northern Bald Ibises. A key contribution was provided by professional pilot Walter Holzmüller, who joined the project in 2007.
Imprinting
Chicks are taken from nests in zoo colonies when only a few days old. Most have come from the Tierpark Rosegg colony in Carinthia (Austria), but other zoos in Austria, Germany, Switzerland, and the Czech Republic also provide chicks.
The chicks are placed in the care of two human caregivers. Only these foster parents interact with the birds and spend the entire day with them. During the first two weeks of life, parental imprinting occurs exclusively on these two individuals.
We practice what is called socially involved hand-raising. This means that the caregivers interact directly and intensively with the birds. They do not wear masks or use puppets. Only a yellow outer garment is worn to help the birds recognize their caregivers from a distance during later training.
This parental imprinting creates a social bond, which is further strengthened and intensified through the constant presence of the caregivers, daily care, and intensive social interactions with each bird. A strong social bond is essential for the birds to reliably follow their foster parents in the aircraft over hundreds of kilometers.
Exclusive contact with the two caregivers ensures that the birds do not develop a general affinity for humans after release. They can distinguish humans well and recognize their foster parents even after several years.
Flight Training
By the end of May, at about six to seven weeks of age, the Northern Bald Ibises fledge. Flight training begins in early June. The specially established training camp is always set up at the edge of a suitable take-off and landing strip.
Thanks to their intensive bond with their caregivers, the juvenile birds are gradually accustomed to the aircraft, the engine noise, and the large parachute. Initially, the aircraft moves only on the ground without deploying the parachute. Only once the birds reliably follow the aircraft is the parachute used. Flights take place over mowed fields and gradually extend over an increasingly larger radius around the camp.
From mid-July, extended training flights of 70 km or more are undertaken. The aircraft is piloted by Johannes Fritz, with one of the two foster parents seated behind him. The birds follow the aircraft reliably only due to the presence of one of their caregivers.
The Aircraft
Since 2007, two identical ultralight aircraft, the “Xcitor” from Fresh Breeze, have been used. These two-seater paraplanes are equipped with powerful engines and are ideal for the project. Flights are conducted with the “Bigmax” parachute from Nova, which has a surface area of 60 m². This large area allows a maximum flight speed of 46 km/h, precisely matched to the flight speed of the Northern Bald Ibises.
Additionally, the aircraft are equipped with auxiliary fuel tanks, allowing flights of up to five hours. Another special feature is the fully enclosed propeller cage, which largely prevents the birds from touching the propellers.
Migration
In early August, wild Northern Bald Ibises enter migratory readiness and leave the breeding grounds. This is also the time for the hand-raised juveniles to begin their human-led migration.
The migration starts at the training camp. Flights are conducted in daily stages of up to 300 kilometers, depending on weather conditions and geographic barriers. The active flight speed of both birds and aircraft is 40–45 km/h. Tailwinds can increase travel speed to over 100 km/h, while headwinds can slow or even prevent progress.
The flight formation, consisting of an aircraft and the birds, is accompanied by a ground team, usually comprising up to 16 people with different tasks. At least one vehicle accompanies the formation and maintains radio contact. The rest of the team dismantles the current camp after take-off, including the 9 × 12-meter aviary, and drives to the next landing site, usually a small airfield, where camp and aviary are reassembled.
Between flight days, rest days are scheduled, which may be extended due to weather. During these times, the birds remain in the aviary and receive intensive care from their foster parents.
Wintering Sites
Since the historical wintering destination of the Northern Bald Ibises is unknown, the choice of new wintering sites was based on suitability. From 2004 to 2022, the goal of the human-led migration was the WWF oasis Laguna di Orbetello in southern Tuscany. Since 2023, a second migration route has been established, leading to the wintering site in Vejer de la Frontera in southern Spain. This new route, about 2,600 km long, became necessary due to climate change.
In Vejer de la Frontera, Northern Bald Ibises are released as part of the reintroduction project Proyecto Eremita. The resulting sedentary population now comprises three colonies in the region, with around 230 birds. Birds released after the human-led migration join this population until their first return flight to the breeding grounds, usually in their third year.
Release
After arriving at the wintering site, the juveniles are kept in an aviary for several weeks. There, they are gradually weaned from intensive care by the foster parents and acclimated to their new environment. The release is then carried out, usually after equipping the juveniles with GPS transmitters. The free-flying birds typically seek contact with wild conspecifics and integrate into the wintering colony.
By the following spring, immature birds make their first excursions northward. Some juveniles may even reach the breeding grounds. By the time they reach sexual maturity in their third year, the released birds return to their breeding grounds in spring to reproduce. The new juveniles then follow their experienced conspecifics in autumn without further human intervention, creating a new migratory tradition.
