Answer: To save energy.
Step-by-step explanation:
Geese are birds that travel by making a V formation when they migrate from a place to another place ( migration).
The primary reason associated with this is conservation of energy, Each of the bird flies slightly above the bird that in front to reduce the wind resistance.
The birds at the front takes turn and the tired bird shifts at the back. This is done so that they can fly for a longer time without being tired.