Page 72 - The Miracle of Migration in Animals

THE MIRACLE OF MIGRATION IN ANIMALS

Why Birds Fly in V Formations

The leading birds in a “V-shaped” flock reduce the amount of air
resistance for the birds behind them. In this way, birds flying as a
flock save energy and can usually fly at greater speed than birds fly-
ing alone.
When migrating birds fly in a staggered pattern, each is sub-
jected to the same amount of air friction as its neighbor. The advan-
tage of this method of flight stems from what pilots call the “wingtip
vortex.”
An airplane’s wings provide the majority of the lift, but also
cause drag. Air flowing over the top of a wing also tends to flow in-
ward toward the fuselage, while air flowing underneath the wing
tends to flow outward. Along the trailing edge of the wing, these two
airflows meet and form a rotating column of air extending out from
the wingtips. On humid days, cold, moist mornings or when flying
through mist, this so-called wingtip vortex is visible to passengers sit-
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ting next to the wing. There are vortices on both sides of the wing.
Higher air pressure below the wing and the lower pressure above
cause this rotating column of air. The air’s natural tendency to flow
from high pressure to low pressure creates airlift around the edge of
the wing, and birds utilize this flow on their journeys.

The "wingtip vortex"
created by airflow over
a bird’s wings when it
takes off can be
re-created under labo-
ratory conditions.

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