Land birds can fly hundreds of kilometers over open oceans

Migrating land birds are capable of flying nonstop for hundreds or even thousands of kilometers over the open ocean by taking advantage of various atmospheric conditions, according to a study conducted by researchers at the Max Planck Institute of Animal Behavior and the University of Konstanz.

Flying over the seas can be highly dangerous for land birds. Unlike seabirds, they are unable to stop or feed on the water, so they need to fly continuously until they reach land. For centuries, scientists thought that land birds only managed short sea crossings of less than 100 kilometers.

However, a new study published in the journal Proceedings of the Royal Society B has proven otherwise. The researchers placed GPS tracking devices on 65 birds across five species and analyzed 112 sea-crossing tracks over a period of nine years. 

The data revealed that, contrary to popular belief, land birds are capable of flying for hundreds or even thousands of kilometers over open seas and oceans as regular parts of their migration patterns. The oriental honey buzzard, for instance, can cover 700 kilometers during an 18-hour nonstop flight over the East China Sea.

Scientists discovered that in order to accomplish such feats of strength and endurance, land birds take advantage of various atmospheric conditions, such as tailwind, a horizontal wind blowing in the direction of the bird’s flight, or the rising air thermals from the seas known as “uplift,” which help them soar up to one kilometer above the sea surface. 

“Until recently, uplift was assumed to be weak or absent over the sea surface. We show that is not the case,” said lead author Elham Nourani, a postdoctoral fellow in the Department of Biology at the University of Konstanz. “Instead, we find that migratory birds adjust their flight routes to benefit from the best wind and uplift conditions when they fly over the sea. This helps them sustain flight for hundreds of kilometers.”

Such a study can open research pathways to investigate how climate change may affect migration patterns. “Our findings show that many land birds are dependent on atmospheric support to complete their migrations over the open sea, indicating their vulnerability to any changes to the Earth’s atmospheric circulation patterns,” explained Dr. Nourani. 

“Collaborative studies like this are important to unravel general patterns about how migratory birds depend on the weather patterns. This enables future studies to make robust predictions about how these birds will be impacted by climate change.”

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By Andrei Ionescu, Earth.com Staff Writer