Swifts' secret to flying high
26 April 2007
Swifts are born aerial acrobats and now scientists have revealed how they manage it. The results boost our understanding of bird behaviour and could help engineers design flying robot spies and energy-efficient aircraft. Antenna takes to the skies...
This research was published in the journal Nature on 26 April 2007.
Image: Jean-Francois, jfc@jfcornuet.info
Swifts spend almost their entire life in the air. They hunt, eat, sleep and even mate on the wing. They can cover huge distances in their lifetime - up to half a million kilometres. That's about the same as flying to the Moon and back six times.
Swifts constantly change the position of their wings while flying - behaviour which experts thought might be a strategy to save energy while making glides, swoops and turns. But now, for the first time, scientists have studied real swift wings to see if the theory is true.
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Swifts only land to lay their eggs. Even then they're not fully grounded; they build their nests in cliff crevices and trees, and on high-rise buildings.
Image: Graham Catley, nyctea.co.uk
So what did the scientists do?
The researchers took a few tips from aircraft engineers - and tested swift wings in a wind tunnel. They took their sample wings from swifts that had died of natural causes and mounted them at different angles to test their aerodynamics at different flight speeds.
Image: David Lentink
'We found that different wing shapes performed much better at particular speeds. At higher speeds and for sharp turning it was better to sweep the wings backwards. But at lower flight speeds it was much more energy efficient to spread the wings out fully,' explains lead researcher David Lentink.
David Lentink from the Experimental Biology Department at Wageningen University was part of a team of ten Dutch and Swedish researchers who helped with the project.
Image: David Lentink
'Even quite subtle changes in the birds' wing shape make a lot of difference to how long and how far they can fly. These results show that swifts can increase their performance by as much as three times by changing their wing shape.'
Swifts extend their wings right out like this when they're flying slow and straight on.
Image: Jeff Blincow
These results will help researchers understand why birds fly as they do. But they could also have interesting uses in other fields. Bret Tobalske, a bird-flight expert explains...
'At the moment there is really intense research into bird-sized robots that can carry a camera and fly through gusty winds. These mini planes could be used by the military to survey terrain, or for fire-fighters in search and rescue missions.'
Bret Tobalske, Professor of Biology, University of Portland.
'The problem with using mini helicopters or planes is that they're not very stable. A little bit of wind means they crash and break. Swifts encounter high winds and can fly at speeds of 30 kilometres per hour while remaining stable. So understanding their optimal wing shapes and energy-saving style could be really important.'
Image:stockxchng.com/Helmut Artmeier
David thinks bird robots could be useful for monitoring animals too. 'We're now starting to design our own micro-aeroplane that can morph its wings. If we're able to design a small swift robot it could fly with the birds and help study their behaviour, which would be great.'
'These results could also help make full-size planes more fuel efficient. Morphing aircraft that can adjust their wing shape are a hot topic at the moment. These designs are mostly inspired by bird wings, but nobody had actually measured how morphing wings work until now,' says David.
Planes that can morph their wings are the next big thing in aeroplane design.
Image: NASA
'Our research confirms the idea that morphing wings really improves the flight performance of birds. It also provides inspiration for future aircraft design based on real results, not just pretty pictures of birds in flight.'
The next step will be to put these results into practice and get 'swift-inspired' aircraft off the ground.