Thermal sailors

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The black kite is a thermal sailor

A thermal sailor , also a glider , is a migratory bird in ornithology that uses the thermals to ascend. Then the bird can cover a longer distance in the desired direction of migration, losing height. These birds are often characterized by broad, board-shaped, often deeply fingered wings. These are often large, relatively heavy birds, which, due to their weight, are not able to cover long distances in powered flight. Since thermal only occurs during the daytime, thermal sailors are day-goers. Thermal sailors generally avoid flying over large areas of water, as there are hardly any thermal currents there. Many storks , cranes , birds of prey and pelicans are thermal sailors.

Thermal sailing or thermal gliding only consumes around 15 to 30 percent of the energy that has to be expended in flapping flight , but has the disadvantage that the pulling distance can be increased to almost double by circling when ascending. Good thermal gliders lose about 10 meters in height on a 100 meter flight distance, so they achieve a glide ratio of 1:10 or a glide ratio of 10.

The term slider is also often used.

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