Bairlein et al.
Bairlein F, Fritz J, Scope A, Schwendenwein I, Stanclova G, van Dijk G, Meijer HAJ, Verhulst S & Dittami J 2015.
Energy Expenditure and Metabolic Changes of Free-Flying Migrating Northern Bald Ibis.
Migratory birds can perform extraordinarily long flights during migration but the physiological processes that make these feats possible have only recently come into focus. It has generally been assumed that flight has high energetic and physiological costs and that the ability to perform long-distance flights was contingent on the evolution of extraordinary physical adaptations to undertake the journey.
Voelkl et al.
Voelkl B, Portugal SJ, Unsöld M, Wilson AM & Fritz J 2015.
Matching times of leading and following suggest cooperation through direct reciprocity during V-formation flight in ibis.
Proceedings of the National Academy of Sciences
One conspicuous feature of several larger bird species is their annual migration in V-shaped or echelon formation. When birds are flying in these formations, energy savings can be achieved by using the aerodynamic up-wash produced by the preceding bird. As the leading bird in a formation cannot profit from this up-wash, a social dilemma arises around the question of who is going to fly in front?
Portugal et al.
Portugal SJ, Hubel TY, Fritz J, Heese S, Trobe D, Voelkl B, Hailes S, Wilson AM & Usherwood JR 2014.
Upwash exploitation and downwash avoidance by flap phasing in ibis formation flight.
Nature, 505, 399-402
Many species travel in highly organized groups. The most quoted function of these configurations is to reduce energy expenditure and enhance locomotory performance of individuals in the assemblage. The distinctive V formation of bird flocks has long intrigued researchers and continues to attract both scientific and popular attention.