Morphing wings are the secret, claim scientists.

A team of Dutch and Swedish scientists claim to have cracked the question of how swifts manage to fly so fast, and with such agility, for so long.

The researchers believe that the results could herald a new era in aircraft design. The secret of the swift lies in its ability to morph it wings into a variety of shapes and angles thereby maximising power and efficiency.

Ten Dutch and Swedish scientists, based in Wageningen, Groningen, Delft, Leiden, and Lund, have shown how 'wing morphing' makes swifts such versatile flyers.

Swifts are the most aerial of birds. They migrate annually from South Africa to Europe, and cover 4.5 million kilometres over their lifetime, a distance equal to six round trips to the Moon or 100 times around the Earth.

During flight, they continually change the shape of their wings from spread wide to swept back, the scientists explained.

When they fly slowly and straight on, extended wings carry swifts 1.5 times farther and keep them airborne twice as long. To fly fast, swifts need to sweep back their wings to gain a similar advantage.

The study proves that swifts can improve flight performance by a factor of three, making 'wing morphing' the next big thing in aircraft engineering, according to the scientists.

Swifts spend almost their entire life in the air, eating, sleeping and even mating on-the-wing, and only landing on cliffs to lay eggs and rear chicks. In fact, if a swift lands on the ground it is unable to take off again without assistance.

Morphing wings are the latest trend in aviation. The best wing shape to save fuel costs depends on flight speed.

In 2003, birds inspired Nasa to design a revolutionary "morphing wing" aircraft as well as so-called micro-aircraft, which are the size of a bird, to exploit the benefits of varying wing shape.

These tiny flyers, equipped with cameras and sensors to assist in surveillance and espionage, imitate faithfully the flight behaviour and appearance of birds.

In an ongoing project, students at Delft University are cooperating with scientists at Wageningen to make such a small airplane fly like a swift.

"The aerodynamics of bird flight is fascinating," said David Lentink, a zoologist at Wageningen University.

"My work in this field was triggered by a biomechanics practical for which I wanted to design a new balance system. I designed it such that it was ideal for measuring the aerodynamic turning performance of gliding swifts."

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