How Land Bird Cross The Open Sea

Migrating birds always choose the routes with the maximum wind speed and high uplift conditions, which help them reduce the energy cost during flight. This is how birds fly non-stop for hundreds of kilometres over the sea.

However, after flying hundreds of kilometres, crossing such a wide-open sea can be dangerous for land birds. Unlike seabirds, land birds can not sustain on the water for food and rest. Hence, land birds have to cross the sea only in one flight. Despite such a danger, land birds can fly for hundreds or even thousands of kilometres over the wide-open seas and oceans as a regular part of their migration. Now, the question arises, how land birds have accomplished this ability?

No doubt, flapping is an energetically costly activity and sustaining in non-stop flapping flight for hundreds of kilometres would not be possible for large, heavy land birds.

Studies have shown that tailwinds help the birds to sustain long journeys. A horizontal wind blows in the bird’s direction of flight, which reduces the energy cost. A single species – the osprey – used rising air thermal energy known as “uplift” to solar over the open sea. The new findings of land bird migration confirm tail wind’s role in facilitating sea crossing behaviour and reveal that the widespread use of uplift means less drag, making sea crossing less energetically demanding. For example, the oriental honey buzzard flies 700 kilometres over the East China Sea during its annual migration from Japan to Southeast Asia. Roughly 18-hour non-stop sea crossing is conducted by flies in autumn when the conditions are favourable. Not only this, by using the uplift, these birds can soar up to one kilometre above the sea surface.

Many land birds depend on the atmospheric condition for their flight, indicating the vulnerability of change in the earth’s atmospheric circulation pattern.

Many more questions need to be answered, like how the weather pattern affects the migrations of birds. And how these birds will be impacted by climate change.

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