Why do migrating birds fly in V-Shape?

 

   It has been observed that as each bird flaps its wings, it creates uplift for the bird immediately behind . By flying in a "V" formation, the whole flock adds at least 71% greater uplift force rather  than   each bird flew on its own. Whenever a goose falls out of formation, it suddenly feels the  resistance  to go through   alone and quickly gets back into formation to take advantage of the power of the flock. The "V" -shaped formation that the migrating birds use when migrating serves two important purposes:
First, it conserves their energy. Each bird flies slightly above the bird in front of him, resulting in a reduction of wind resistance. The birds take turns being in the front, falling back when they get tired. In this way, the birds can fly for a long time before they must stop for rest.
The second benefit to the "V" formation is that it is easy to keep track of every bird in the group. Fighter pilots often use this formation for the same reason. Finally, when one among the bird gets sick or is wounded by a gunshot and falls out, two birds fall out of the formation and follow the injured one down to help and protect him. They stay with him until he is either able to fly or until he is dead, and then they launch out with another formation to catch up with their group.