Page 60 - Design in Nature

58 DESIGN IN NATURE

Thermal soaring is a phenomenon observed
especially in warm inland areas of the globe. As the
sun heats the ground, the ground in turn heats the air

above it. As the air gets warmer, it gets lighter and
starts to rise. This event can also be observed in dust
storms or other wind whirls.

The Soaring Technique of Vultures

Vultures utilise a special method in order to
scan the earth below from an appropriate height
riding rising columns of warm air, called
the thermals. They can continuously
make use of different thermals to sustain their
soaring over very large areas for very long

times.
At dawn, airwaves start rising.
First, smaller vultures take off, riding weaker currents. As currents become
stronger, larger birds take off as well. Vultures almost float upward in these
ascending currents. The fastest rising air is located in the middle of the

current. They fly in tight circles in order to balance uplift with gravitational
forces. When they want to ascend, they draw closer to the centre of the
currents.
Other hunting birds use thermals as well. Storks make use of these
warm air currents, especially when migrating. The white stork lives in
central Europe and migrates to Africa for winters on a journey of about 4350

miles (7000 kilometres). If they were to fly solely by flapping their
wings, they would have to rest at least four times. Instead, the
white storks complete their flights in three weeks by utilising
warm air currents for up to 6-7 hours a day, which

translates into big energy savings.