Too romantic nature can assert that swallows – extraordinary birdss, endowed with a special instinct and intuition, they are able to feel the weather change and his behavior to warn about it.
However, everything is much easier. Enough to appeal to the school physics course and remember the law of gravity (F=mg) in order to explain the behavior of swallows before rain.
Swallows are birds of prey that feed themselves and their Chicks suckling the smallest of insects and midges in abundance living in the air and not always noticeable to the naked human eye.
Shortly before it rains, humidity is significantly increased. As a result, on the wings of the insect are deposited tiny droplets of water. This leads not only to an increase in the severity of the wings, but also to increase the body mass of the insect, whose activity is accordingly reduced. Gnats, bugs, etc. are forced to fly lower than usual. Therefore, their pursuers – swallows - down in his flight closer to the surface of the earth.
Man, unable to see the true reason for this flight of birds, ascribes the signs of extraordinary abilities and capabilities.
But not only the approaching rain can "make" the swallows to change the usual altitude. Sudden changes in temperature, for example cooling of the evening, lead to the same effect. And again, the reason lies in the changing at the same time, a lower flying insects. Therefore, virtuosic, exciting "dance of swallows in the evening sky is not always the harbingers of bad weather.
The younger generation of these beautiful birds often "rejects" became a familiar sign. And even during small precipitation can be observed high in the sky frolicking swallows. The fact that the unencumbered production of food "youths" work out new skill – flying.