Flying in a flock comes at a cost in pigeons

一群鸟以V型队列飞翔，可以减小空气阻力，节约能量消耗。但是以更紧密的别的队列飞行，阻力或能量消耗却要增加。看来packing的方式对能量消耗有很大影响。动物世界真有意思。开一个label "Animal-study'.

The picture is from NATURE

Flying in a flock comes at a cost in pigeons Nature 474, 7352 (2011). doi:10.1038/nature10164 Authors: James R. Usherwood, Marinos Stavrou, John C. Lowe, Kyle Roskilly & Alan M. Wilson 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.

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Aerodynamics: The cost of flight in flocks
Nature 474, 7352 (2011). doi:10.1038/474458a
Authors: Geoffrey Spedding
There are well-known aerodynamic and energetic benefits to flying in an orderly formation. By contrast, it seems that the flocking flight seen in pigeons is metabolically expensive. So why do they do it?