My father used to say when the birds fly low there is a storm coming. He said the birds fly low because the insects they hunt then fly low. My question now is why the insects do that?
Answer
Insect-eating birds and their prey do indeed fly lower when there is less rising air. The air rises when it warms (for example, because the earth, after being warmed by the sun all day, will warm the lower layers of the air). We have good weather especially when we are in an area of ​​high air pressure. So in good weather we have thermals and the insects fly high.
In cold weather you have little thermals and the insects fly low. Severe thunderstorms mainly occur in a transition area from very warm to much colder weather. In such an area you can still find strong thermals, but also downdrafts and strong winds. Insects don’t like to fly in such conditions and they will descend on their own. During the thunderstorm, the temperature can drop very quickly and the earth cools further, causing the thermals to disappear.
Answered by
Dr. Reginald De Deken
entomology and tropical veterinary medicine
Nationalestraat 155 2000 Antwerp
http://www.itg.be/
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