Page 85 - The Miracle of Migration in Animals

HARUN YAHYA

Utilizing the Wind in Flight

Radar research conducted during both spring and autumn mi-
grations has shown that the weather and in particular, heat, plays an
important part in a bird’s decision as to when to start migrating.
Wind is one important factor influencing the start of flight. In spring,
they are the winds blowing from the south and from the north in au-

tumn. Clear weather conditions that let birds easily determine their
route from the sky is a second important factor.
For gliders like the falcon, the osprey, the eagle and the vulture,
proper wind conditions are essential. For falcons that migrate along
the mountains in the eastern United States, the second day after the
passing of a cold front is ideal, since steady northwesterly-west
winds lift the gliding birds above the mountain ridges that run north

Birds that are heavy in rela-
tion to their wing span (such
as swans and ducks) must
flap their wings constantly,
using five times more en-
ergy than gliding birds.

This technique used by large
birds such as cranes and
birds of prey lets them
switch over at the peak from
flapping their wings to glid-
ing.

Small birds like wood war-
blers and fieldfares fly by al-
ternating between flapping
their wings and holding
them in. This lets them co-
ver distances by dropping
down and then rising again.

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