+ The V formation greatly boosts the efficiency and range of flying birds, particularly over long migratory routes. 
+ All the birds except the first fly in the upwash from the wingtip vortices of the bird ahead. 
+ In a V formation of 25 members, each bird can achieve a reduction of induced drag by up to 65% and as a result increase their range by 71%. 
+ The birds flying at the tips and at the front are rotated in a timely cyclical fashion to spread flight fatigue equally among the flock members.

USA Today: "Why birds fly in a V-formation" by Traci Watson January 15, 2014, http://www.usatoday.com/story/news/nation/2014/01/15/birds-flying-v-formation/4475687/