Swarming migratory birds in the impressive formation of a “V”: Most of them have already marveled at this fascinating natural spectacle in the sky. Scientists have now gone one step further and have immediately joined the swarm. Using an ultralight aircraft, they even took on the role of guide bird. They wanted to find out something that was previously only known theoretically and could only be simulated with mathematical models: How do birds manage to save energy through their cooperative behavior during their migratory flight? Energy efficiency is an important survival factor.

The international research team led young bald ibises to their Italian winter quarters to find a new Win record. The predominantly Austrian research group also includes two doctoral students from Italy and Israel; other partners come from the University of Veterinary Medicine, Vienna, the Joanneum University of Applied Sciences in Graz and the University of Bern.

Data logger on each bird Already in the years 2018 and 2019 two groups of young birds. During this first migration from Überlingen (Lake Constance), they covered around kilometers to their winter quarters in southern Tuscany (WWF Oasi Laguna di Ortobello) back. The journey lasted two weeks, including six to seven flight days, during which the Alps and the Apennines were crossed and altitudes of up to 2900 meters were reached. The birds were all raised by human hands. Thus they could be equipped with an extra light “data logger” that was assembled and disassembled every day. “The data logger does not transmit any data, it saves it internally. It was particularly challenging for us to achieve the extremely high level of precision to within a few centimeters,” sums up research director Johannes Fritz, biologist, conservationist and bald ibis expert.

What interested the team most were the exact positions of the individual animals and their relationships to each other – these could be recorded thanks to three global satellite navigation systems (GPS, Galileo, GLONASS). It was clear that the guide bird would play a decisive role in saving energy. Only which? Originally, the team assumed that this would benefit the least from the structure. But they were surprised: “In a preliminary study we found out that the animals take turns, but assumed a rather static system with a leader. In the current research project we observed much more dynamics than expected. Each animal was in both the Lead and follow-up function, which means that everyone benefits, “explains Fritz.

Exact distances and wing beats In order to save energy collectively, an exact choreography in the flight structure is decisive: distance to the person in front and exact synchronization of the flapping of the wings. Motion sensors in the data loggers therefore measure both the frequency of the wing beat and the position of the wing. In the case of four separately reared young birds, the heart rate was also recorded using electrodes in order to be able to calibrate these values ​​with the metabolic energy expenditure under laboratory conditions and to enable conclusions species protection is becoming more and more relevant. The data records are currently still being evaluated. Fritz and the team suspect that the energy savings between 15 and 30 percent will be. This is a significant value, especially for inexperienced young birds with low productivity. The research project will run until the end 2021 and is financed by the FWF Science Fund. (bsc)