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CHAPTER 4 III The Wing: Particulars of Flight 55
A B
C D
Figure 4-17 • A, A tern hovers above the water’s surface searching for minnows. Spotting its prey, the tern plummets toward the water’s
surface (B), folding its wings upward at the moment of entry (C). D, After a successful attack, the tern flies off to complete its meal in
calmer waters.
III PROPULSION as described in an earlier section. When birds fl y long
distances, they alternate between flying and gliding,
Most birds fly with an action that loosely resembles similar to a cyclist who alternates between peddling
swimming, specifically a hybrid stroke, combining ele- and coasting. Drafting is common, with the lead posi-
ments of the breast and butterfly strokes. Birds literally tion of the V-formation changing frequently. When
pull themselves through the air. They maintain their possible, birds rest and feed regularly. Figure 4-18
course by continually adjusting their control surfaces, illustrates the elements involved in avian fl ight.
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