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Compared with running and swimming, the speed achieved during
flight is very high. For example, the fastest running cheetah manages
80 kilometers/hour (49.7 miles an hour). The fastest swimming fish, the
sailfish, reaches a maximum of 10 kilometers/hour (6.2 miles an hour),
while a hawk can attain up to 300 kilometers/hour (186.4 miles an hour)
as it dives with its wings folded. (1) Moreover, in comparison with the
distance traveled, the energy expended is far less than that in swim-
ming or running. A cheetah, for instance, reaches its top speed in 3
seconds, but must expend a high level of energy to overcome inertia.
Its internal body temperature reaches 40°C during this process. In
terms of energy expended over distance traveled, therefore, birds have
been created with an incomparably more efficient structure.

1. John Downer, Supernature, The Unseen Powers of Animals, Sterling Publishing Co., Inc.,
New York, 1999, ss. 114-117.