The birds fly in V-formation because birds are smarter than you realize. They sync themselves together carefully positioning their wingtips so as to catch the updraft from the bird in front and to the side of them. This practice saves energy. If you think about this, it makes perfect sense. They would be tuckered out by the time they reached their destination miles and miles away from where they started their flight. There was a study done on this by scientists and printed in Nature magazine.
It’s estimated the birds use 20-30 percent less energy flying in V-formation. They have to remain careful and aware of their neighbor at all times. No one knows how they decide on the course and how the leader picks to appropriate place to start. Birds seem to be smarter than you think. Their survival depends on it.