Page 87 - The Miracle of Migration in Animals

HARUN YAHYA

Pelicans migrate using rising columns of warm air known as thermals. They
find these invisible elevators by the low-frequency sounds emitted by the
vortices of rising air.

Heated air gives off a low-frequency sound that can be per-
ceived by migrating birds from a distance of 3 kilometers (2 miles).
Although not all migrating birds make use of thermal heat, these
low-frequency sounds help them in other ways, too. For example, the
rhythmic sound of ocean waves can be heard even at great distances
from the shore. But at a distance where all high-frequency sounds are
absorbed, it becomes a low roar. At an even greater distance, these
sounds become completely inaudible. If our sense of hearing were as
strong as that of birds, we would be able to hear sounds from even
hundreds of kilometers away. While this is impossible for us, it’s pos-
sible for birds thanks to the fact that they can hear extreme infra-
sound, as low as one cycle every ten seconds. At these frequencies,
sound can travel almost unhindered. As well as the infrasound of the
ocean, birds can perceive other distant sounds such as wind on
mountain slopes and shifting desert sands. Migrating birds may be
able to listen to the changing patterns of these distant sounds and use

them as acoustic signposts. 26

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