Have you ever wondered how birds travel hundreds of kilometers in air without stopping?

Migratory birds in V formation, Scientific American

Abe V Rotor

Study a flock of geese in flight arranged in V-formation. The stronger ones take the lead while the others follow behind. Now and then there is shifting in role to give those in the lead to take respite before it will be their turn gain. This arrangement follows the laws of physics to overcome air resistance and make flying easier. It is designed for a dozen birds or so, that typically make a flock. That is why during mass migration you will notice a number of flocks independently cruising the sky in Vs and keeping in safe distance from each another - indeed a marvel in air navigation, a built-in instinct developed through thousands of years of evolution.

There is a movie, Fly Away Home, based on a true story. It is about a girl guiding a flock of geese with a portable aeroplane all the way from Canada to their sanctuary in the US, simulating the natural migration of birds. ~