Flights of Fancy by Richard Dawkins

Author:Richard Dawkins [Dawkins, Richard]
Language: eng
Format: epub
Publisher: Head of Zeus
Published: 2022-11-18T00:00:00+00:00

© Shutterstock. Contributor: Hand with card (Maisei Raman)

CHAPTER 8

POWERED FLIGHT IN ANIMALS

CHAPTER 8

POWERED FLIGHT IN ANIMALS

Animal flight is more complicated and difficult to understand than that of human machines. This is partly because flapping wings drive the animal forwards (the plane principle) at the same time as they thrust air downwards (more like a helicopter). If you watch a flying bird in a slow-motion film (you need slow motion to even hope to see what is going on) you’ll notice that the wings are not simply flapping up and down. The curvature of the wings combined with the supple bendiness of the feathers propels the bird forwards, which in turn provides lift by the two methods we saw in Chapter 7, the Newtonian and Bernoullian methods. At the same time, the downstroke of the wings provides lift in its own right, as we saw at the beginning of Chapter 7, the helicopter part. The upstroke doesn’t spoil things by having the reverse effect that we might naively expect. This is partly because of the curvature of the wing, and partly because it twists during the upstroke, and the elbow and wrist joints pull inwards so the area of the wing is reduced compared to the powerful downstroke.

Lacking propellers or jets, birds and other flying animals use their wings to propel themselves forwards as well as to provide lift directly. This is unlike man-made planes, whose wings provide lift but not forward propulsion. The opposite extreme, where wings are exclusively concerned with forward propulsion but not lift, can be seen in penguins, but that’s underwater of course, rather than in air. Penguins are buoyant, lighter than water, so they don’t need wings for lift. Instead, they use their wings for ‘flying’ underwater. Unlike on land where they waddle with a slow, ungainly gait, penguins streak through the water extremely fast like dolphins, although dolphins propel themselves in a different way, using up and down movements of the tail. Both dolphins and penguins are beautifully streamlined. Streamlining would have come easily to the ancestors of penguins, already streamlined for flying through the air.

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