The orientation and navigation skills of migratory species fascinate scientists. Today, tracking them is accurate and easier thanks to the use of satellite tags attached to the animals. In October 2022, scientists thus awarded the title of migrant that made the longest journey without a stopover, the red-billed bird, a bird that visits wetlands. The bird flew for more than 11 days and traveled 13,560 kilometers without landing. World record.
But how do migratory birds navigate and refine their trajectory over the years? Scientists from the University of Wyoming and the Max Planck Institute tried to answer this last question by studying in detail the migrations of white storks (Ciconia ciconia). Their results were published in a journal Proceedings of the National Academy of Sciences (PNAS).
Advantages of surveying
Using solar-powered GPS beacons, researchers recorded the migration of more than 250 white storks between 2013 and 2020. They were able to track the birds during their spring migration between North Africa and their home breeding grounds in Germany and Austria. All details of the trip are recorded, from the route to the bird’s speed and stopovers.
From these results, the scientists were even able to estimate the energy expenditure of each individual during its flight. The result: the chicks find time to explore the surroundings, even if it means a detour, but as the birds get older, their migration becomes more and more efficient.
“Older individuals stop exploring new places and move faster and more directly”, analyzes Ellen Aikens, lead author of the study. Their spatial memory develops with experience, allowing them to use shortcuts from one year to the next. An operation that they believe could affect other migratory animals. “Storks gradually straightened their migration routes to find more direct ways to travel from Africa to summer breeding grounds in Europe,” analyze researchers.
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“Storks switch from an energy-saving strategy to a time-saving strategy”
But these new, more direct pathways also lead to greater energy expenditure… The researchers summarize: “Storks Switch From Energy Saving Strategy”, with more frequent stopovers among young people, “on a time-saving strategy because they’re getting old.” Behavior that can be explained mainly by competition for food resources at the point of arrival.
When it comes to explaining migration behavior, scientists have long deferred to the consequence of learning. Genetic factors and social behavior are indeed important in understanding migration. However, according to this new study, it appears that information received individually also shapes the behavior of birds. “Lifelong learning represents an additional and complementary mechanism that shapes animal migration,” the authors conclude.