What determines where migratory songbirds spend the northern winter in Africa? A new study suggests that their journeys are guided not only by instinct but also by the environment in which they were raised.
The study, published in Science, also provides new insights into how climate change and habitat loss could affect bird populations across the continent.
Researchers tracked pied flycatchers from breeding grounds across Europe to their wintering habitats, which stretch from Senegal in West Africa to the Central African Republic. They also conducted a five-year experiment in which bird eggs were swapped between nests in the Netherlands and Sweden.
The study revealed that both inherited traits and early-life experiences influence where the birds spend the nonbreeding season in Africa.
“We show that both inheritance and natal environment determine nonbreeding areas,” the researchers wrote.
The findings suggest that migration destinations are shaped by a combination of genetics and upbringing.
The researchers also found that although birds from different European countries follow a common migration corridor through Spain and along the west coast of Africa, they eventually disperse to distinct wintering grounds across the continent.
Some populations remain concentrated in West Africa, while others continue farther east, creating strong links between specific breeding populations in Europe and particular African ecosystems.
The researchers also discovered that the birds do not take the shortest route to Africa. Instead, they make a lengthy detour through the Iberian Peninsula before crossing the Sahara, with some birds flying thousands of extra kilometers.
Scientists believe this ancient migration route has been passed down through generations and remains deeply embedded in the birds’ behavior.
The study underscores Africa’s critical role in the survival of millions of migratory birds.
Healthy forests, savannas, and wetlands across the continent provide essential winter habitat, meaning that habitat degradation and climate change in Africa could directly affect bird populations that breed thousands of kilometers away in Europe.
“Our experiment shows that nonbreeding site distribution in this long-distance migrant songbird is shaped by a mixture of inheritance and natal environment,” the researchers wrote.
However, they warn that because migration routes are partly inherited, birds may struggle to adapt rapidly to environmental change.
The researchers also found evidence that birds establishing themselves in new breeding areas can gradually create new migration links between Europe and Africa, offering hope that the species can adapt over time.
“Although an inherited basis for migratory routes and nonbreeding areas may hamper rapid adaptation to a changing world, dispersing individuals can create new breeding–nonbreeding site combinations,” the study stated.
IMAGE CREDIT