title: Flying in a flock comes at a cost in pigeons.
abstract: Flying birds often form flocks, with social, navigational and anti-predator implications. Further, flying in a flock can result in aerodynamic benefits, thus reducing power requirements, as demonstrated by a reduction in heart rate and wingbeat frequency in pelicans flying in a V-formation. But how general is an aerodynamic power reduction due to group-flight? V-formation flocks are limited to moderately steady flight in relatively large birds, and may represent a special case. What are the aerodynamic consequences of flying in the more usual 'cluster' flock? Here we use data from innovative back-mounted Global Positioning System (GPS) and 6-degrees-of-freedom inertial sensors to show that pigeons (1) maintain powered, banked turns like aircraft, imposing dorsal accelerations of up to 2g, effectively doubling body weight and quadrupling induced power requirements; (2) increase flap frequency with increases in all conventional aerodynamic power requirements; and (3) increase flap frequency when flying near, particularly behind, other birds. Therefore, unlike V-formation pelicans, pigeons do not gain an aerodynamic advantage from flying in a flock. Indeed, the increased flap frequency, whether due to direct aerodynamic interactions or requirements for increased stability or control, suggests a considerable energetic cost to flight in a tight cluster flock.
authors.affiliation: Structure and Motion Laboratory, The Royal Veterinary College, University of London, North Mymms, Hatfield AL9 7TA, UK. jusherwood@rvc.ac.uk
authors.forename: James R
authors.initials: JR
authors.lastname: Usherwood
authors.forename: Marinos
authors.initials: M
authors.lastname: Stavrou
authors.forename: John C
authors.initials: JC
authors.lastname: Lowe
authors.forename: Kyle
authors.initials: K
authors.lastname: Roskilly
authors.forename: Alan M
authors.initials: AM
authors.lastname: Wilson
mesh_terms: D000054:Acceleration; D000818:Animals; D001696:Biomechanical Phenomena; D001835:Body Weight; D010856:Columbidae / Q000033:anatomy & histology / Q000502:physiology*; D004734:Energy Metabolism; D005426:Flight, Animal / Q000502:physiology*; D040362:Geographic Information Systems; D008954:Models, Biological; D012919:Social Behavior; D013997:Time Factors; D014921:Wings, Animal / Q000502:physiology