© Wouter Vansteelant
A 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.
A 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.
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: Just to underscore this rising trend in fatal elephant attacks, see this June, 2021 report concerning the situation on the nearby island of Sri Lanka: