Migrating is strenuous for birds. Therefore, they need to find energy-saving strategies, such as flying in a V-formation. In a V-formation, birds take advantage of the up-wash produced by the preceding bird. Yet, the trailing bird does not get any benefit, hence birds switch their positions inside the flight formation. I hypothesize that every individual contributes to the flying effort and hence there is a pattern in the switches, which may be also affected by social relationships.