THE dark side
African Birdlife|November/December 2021
Do dark upperwings improve flight performance?
PETER RYAN

It is well known that heating the up-per side of an aerofoil decreases the drag induced by air friction, thus making the aerofoil more efficient. It has therefore been speculated that one reason why birds might tend to have darker upper wings is to improve their flight efficiency. This might sound somewhat unlikely, but a recent paper by Svana Rogalla and colleagues provides some evidence for this effect in seabirds (J. R. Soc. Interface 18: 20210236).

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