Millions of migratory birds occupy seasonally favorable breeding grounds in the Arctic, but scientists know little about the formation, maintenance and future of the migration routes of Arctic birds and the genetic determinants of migratory distance.
In new research, a multinational team of researchers established a continental-scale migration system that used satellite tracking to follow 56 peregrine falcons (Falco peregrinus) from six populations that breed in the Eurasian Arctic, and sequenced the genomes of 35 birds from four of these populations. They found that a gene called ADCY8 is associated with population-level differences in migratory distance.
“Previous studies have identified several candidate genomic regions that may regulate migration — but our work is the strongest demonstration of a specific gene associated with migratory behavior yet identified,” said co-author Professor Mike Bruford, a molecular ecologist in the School of Biosciences at Cardiff University.
For the study, Professor Bruford and colleagues tagged 56 Arctic peregrine falcons and tracked their journeys by satellite, following their annual flight distances and directions in detail.
“Peregrines initiated their autumn migration mainly in September, traveled 2,280-11,002 km in about 27 days and arrived at their wintering areas mainly in October,” they said.
“Peregrines migrate solitarily; birds that depart from different breeding grounds use different routes, and winter at widely distributed sites across four distinct regions.”
“Individual birds that were tracked for more than one year exhibited strong path repeatability during migration, complete fidelity to wintering locations and limited breeding dispersal (5.37 km on average).”
“All populations demonstrated a high degree of migratory connectivity, which suggests strong selection for long-term memory.”
The scientists found that the birds used five migration routes across Eurasia, probably established between the last Ice Age 22,000 years ago and the middle-Holocene 6,000 years ago.
They used whole genome sequencing and found a gene — ADCY8, which is known to be involved in long-term memory in other animals — associated with differences in migratory distance.
They found ADCY8 had a variant at high frequency in long-distance (eastern) migrant populations of peregrines, indicating this variant is being preferentially selected because it may increase powers of long-term memory thought to be essential for long-distance migration.
“Our work is the first to begin to understand the way ecological and evolutionary factors may interact in migratory birds,” said senior author Professor Xiangjiang Zhan, a researcher in the Institute of Zoology at the Chinese Academy of Sciences.
“We hope it will serve as a cornerstone to help conserve migratory species in the world.”
The authors looked at simulations of likely future migration behavior to predict the impact of global warming.
If the climate warms at the same rate it has in recent decades, they predict peregrine populations in western Eurasia have the highest probability of population decline and may stop migrating altogether.
“In this study, we were able to combine animal movement and genomic data to identify that climate change has a major role in the formation and maintenance of migration patterns of peregrines,” Professor Bruford said.
The results were published in the journal Nature.
Z. Gu et al. Climate-driven flyway changes and memory-based long-distance migration. Nature, published online March 3, 2021; doi: 10.1038/s41586-021-03265-0
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