Scientists track mongrel eagles as war breaks out in Ukraine, leading to a surprising discovery



The war in Ukraine has much more far-reaching consequences for nature than previously thought. For example, mongrel eagles have to make a long detour with fewer rest breaks in between, according to new research.

When the scientists started their research in 2017, they certainly did not intend to follow mongrel eagles through a battlefield. Yet that is what ultimately happened: the Russian invasion of Ukraine suddenly gave European scientists the unique opportunity to measure the effect of a war on the migration pattern of the greater spotted eagle. This bird species is virtually impossible to find in Europe anymore, except in one place: Polesia, in Belarus. This is where the very important breeding grounds of the bird species are located. However, the birds’ habitats are in Africa and the Middle East, meaning the birds have to fly over Ukraine to get to Polesia. This journey suddenly takes much longer: the birds no longer feel safe in Ukraine, so they completely avoid parts of the country. This detour provides an average extension of 85 km.

Scientist Adham Ashton-Butt contributed to the research. Ashton-Butt added: “Migratory bird species, such as the greater spotted eagle, are having a tough time around the world. It is therefore essential to understand what effect humans ultimately have on these animal species. Our results clearly show that human behavior can be very disruptive to wild animals living in nature.” The research has been published in the journal Current Biology.

Migration behavior
Before the original study, the researchers were already busy tagging mongrel eagles in 2017 by giving them a trackable chip. In total, the scientists managed to track 21 hybrid eagles. The original goal was to track the bird species in order to discover important (resting) places that the birds often used. The research started already in 2018, which later turned out to be essential: the period from 2018 to 2021 would later provide important reference data that could be used for a direct comparison between normal migration behavior and migration behavior in wartime.

While analyzing the migration data, the researchers quickly noticed that mongrel eagles take much fewer rest breaks in Ukraine during wartime. In the period before the war, an average of 90% of all mongrel eagles took a rest in Ukraine, while in wartime this percentage had dropped to 30%. Migration also took a lot longer: female mongrel eagles needed an average of 246 hours for their journey to Belarus, while previously this route took an average of 193 hours. The same longer flight time can also be found with male mongrel eagles: before the war it took an average of 125 hours for a male mongrel eagle to arrive in Polesia, while during the conflict it suddenly took 181 hours.

Mating behavior
The results of the study are significant because the longer flight time ultimately means that the birds arrive at their destination in a worse condition. As a result, they are not at their physical strongest, which can ultimately have disastrous consequences for mating behavior. Ashton-Butt concludes: “We have observed similar responses in bird species that frequent military training zones. These new results show that the impact of these disturbances ultimately has a much greater impact on migratory species. This effect was so strong that we could even observe it in a smaller test group.”