Peregrine falcons travel thousands of kilometers to get from their breeding areas to their winter quarters. Researchers have now identified a gene that determines how far individual populations migrate. The gene is associated with the long-term memory of animals. In addition, the researchers evaluated how various flight routes have established themselves over the past millennia. According to the results, climatic environmental changes played a major role. In the future, climate change could affect the migratory behavior of the hawks and endanger their populations, warn the authors.
With a top speed of 320 kilometers per hour, peregrine falcons are the fastest animals in the world. Twice a year they cover enormous distances of sometimes more than 10,000 kilometers when they switch between their breeding and winter quarters. Peregrine falcons, which breed in the Arctic and overwinter in South Asia or Africa, migrate particularly far. Animals from a population usually maintain similar routes, but fly individually on their own path.
Long and short haul flyers
A team led by Zhongru Gu from the Chinese Academy of Sciences in Beijing has now dealt with the behavior, genetics, history and future of the arctic peregrine falcon in an interdisciplinary manner. For their study, the researchers equipped 56 animals from six different arctic populations with small satellite trackers and tracked their migrations for several years. They combined these data with genome analyzes of 35 of the animals. In addition, using data on changes in the landscape since the last Ice Age, they reconstructed how the hiking routes have changed over the millennia.
Using the satellite data, the researchers first observed that animals from different populations migrated at different distances. For populations with breeding areas in the west of the Russian Arctic, winter and summer roosts were only an average of 3,680 kilometers apart, while populations from the eastern Russian Arctic traveled an average of 6,134 kilometers, and the farthest fliers even more than 11,000 kilometers. The peregrine falcons apparently remained largely true to their routes: “Individual birds that we observed over several years always chose a similar route,” the authors report.
Long-term memory gene
When they compared the migration routes with the genetic data of the birds, Gu and colleagues found that a certain variant of the ADCY8 gene is particularly dominant in peregrine falcons with the longest flight distance. “Previous studies have provided evidence that this gene is involved in long-term memory,” the authors report. “Our results show that the mean trail fidelity in long-range peregrine falcons was significantly higher than that of short-range peregrine falcons. To do this, they need a strong long-term memory. ”How far a peregrine falcon migrates is obviously genetically determined and thus a result of natural selection. “Our work is the strongest evidence yet of a specific gene linked to migratory behavior,” says co-author Mike Bruford of Cardiff University in the UK.
Using the genome analyzes, the researchers were also able to reconstruct evolutionary relationships between the various populations. In order to draw conclusions about historical migration routes, the researchers combined this data with information about the development of the Eurasian landscape since the last Ice Age around 22,000 years ago. To do this, they used pollen analyzes, among other things. Accordingly, the breeding areas have probably shifted further north since the last Ice Age. The eastern winter quarters probably already offered the peregrine falcons good conditions during the Ice Age, while the western areas were added later. “From this we conclude that ice age cycles can influence both the direction and the distance of the migrations,” the researchers write.
Threat from climate change
These results are also significant in view of the current climate change. With the help of simulations of future developments, the authors predict that the breeding areas will move further north. According to the simulation, western peregrine falcon populations will lose large parts of their habitat, while eastern populations will have to travel longer and longer distances to find suitable areas. “If the climate warms to the same extent as it has in recent decades, peregrine falcons in western Eurasia could stop migrating altogether and eastern peregrine falcons could be exposed to greater risks, as mortality is positively linked to migration distance,” the authors say.
A decline in stocks can already be observed, which is very likely due to global warming and the associated environmental changes. According to the authors, it is all the more important to pay greater attention to the protection of peregrine falcons and other migratory birds. “In this study, we combined animal movement and genome data and found that climate change plays an important role in the migration patterns of peregrine falcons,” said Bruford. Gus colleague Xiangjiang Zhan adds: “Our work is the first attempt to understand how ecological and evolutionary factors can interact in migratory birds. We hope this will serve as a cornerstone for the conservation of migratory bird species around the world. “
Source: Zhongru Gu (Chinese Academy of Sciences, Beijing) et al., Nature, doi: 10.1038 / s41586-021-03265-0