SOME birds fly more like fighter planes than conventional aircraft, which is why they can make impressively sharp turns when diving for prey.
The wings of a conventional plane push air downwards, and the reaction to this force is what creates lift. Until now, scientists thought that birds鈥� wings generated lift in the same way. Insects, by contrast, are known to use a more complicated mechanism: they rotate their wing tips as they flap. This sets up vortices on the leading edge of the wing that increases the wing鈥檚 effective thickness and hence its lift. Some fighter aircraft have wings designed to generate similar vortices.
Now it turns out that birds鈥� wings create vortices too. When John Videler and Elize Stamhuis of the University of Groningen and David Povel of the University of Leiden in the Netherlands placed the stiffened wing of a dead common swift in a water tunnel loaded with fluorescent particles, they saw that the backward-sweeping, downward-tilting wing generates leading-edge vortices (Science, vol 306, p 1960). 鈥淣ow we know [birds] are like very sophisticated airplanes,鈥� Stamhuis says.
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