Some bird species have refined their flying skills to the extent that they can fly in near-perfect V, but why they adopt such a tactic has been a matter of conjecture. One suggestion is that by flying in a V the birds are able to minimize energy costs, and now an analysis of data captured from free-flying migratory northern bald ibises suggests that there are energetic benefits. The data also reveal a sophisticated and dynamic process of in-flight control. Birds in the V phase their wing-beats to path-match, allowing a trailing bird to exploit the aerodynamic upwash from the bird in front. A bird flying directly behind, however, flaps with opposite phasing in order to minimize the detrimental downwash from the leader's wings. All this must require the birds to have developed a range of phasing strategies to cope with the dynamic wakes produced by flapping wings.
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