Migrating birds choose routes with the best wind and uplift conditions, helping them to fly nonstop for hundreds of kilometers over the sea.
© Wouter VansteelantA dark morph Eleonora's falcon flying off Alegranza islet in the Atlantic Ocean. Despite being powerful flyers, Nourani et al. show that falcons are highly selective of supportive winds during trans-oceanic migration.
Researchers at the Max Planck Institute of Animal Behavior and University of Konstanz in Germany have identified how large land birds fly nonstop for hundreds of kilometers over the open ocean — without taking a break for food or rest. Using GPS tracking technology, the team monitored the global migration of five species of large land birds that complete long sea crossings.
They found that all birds exploited wind and uplift to reduce energy costs during flight — even adjusting their migratory routes to benefit from the best atmospheric conditions. This is the most wide-ranging study of sea-crossing behavior yet and reveals the important role of the atmosphere in facilitating migration over the open sea for many terrestrial birds.Flying over the open sea can be dangerous for land birds. Unlike seabirds, land birds are not able to rest or feed on water, and so sea crossings must be conducted as nonstop flights. For centuries, bird-watchers assumed that large land birds only managed short sea crossings of less than 100 kilometers and completely avoided flying over the open ocean.
However, recent advances in GPS tracking technology have overturned that assumption.
Data obtained by attaching small tracking devices on wild birds has shown that many land birds fly for hundreds or even thousands of kilometers over the open seas and oceans as a regular part of their migration.But scientists are still unraveling how land birds are able to accomplish this. Flapping is an energetically costly activity, and trying to sustain nonstop flapping flight for hundreds of kilometers would not be possible for large, heavy land birds. Some studies have suggested that birds sustain such journeys using tailwind, a horizontal wind blowing in the bird's direction of flight, which helps them save energy. Most recently, a study revealed that a single species — the osprey — used rising air thermals known as "uplift" to soar over the open sea.
Comment: Anyone who would trust Facebook with even more intrusive data collecting is either naive or a complete authoritarian.
See also: