Fly with a little flap from your friends

摘要

The elegant Ⅴ formations of migrating birds provide a picturesque harbinger of summer's end, but why do the birds fly in such a precise formation? There are rumours that Allied bomber pilots during the Second World War noticed that their fuel economy increased when their squadrons flew in a Ⅴ formation. Although these apocryphal tales have not been confirmed, the energy-saving benefits of formation flying have been reported in both civil and military aviation. For example, by maintaining one wing tip in the wake of a forward plane, a fighter jet can reduce its energy consumption by up to 18% (ref. 2). However, exploiting the benefits of formation flight is more challenging for birds than for fixed-wing aircraft - birds not only need to adjust their position relative to each other, but also must synchronize their wingbeat patterns. On page 399 of this issue, Portugal et al. show that at least one bird species exhibits the requisite synchronization of body position and flapping motion to reduce energetic cost during migratorv flight.