Data from: Foraging at the edge of the world: low‐altitude, high‐speed maneuvering in barn swallows

While prior studies of swallow manoeuvering have focused on slow-speed flight and obstacle avoidance in still air, swallows survive by foraging at high speeds in windy environments. Recent advances in field-portable, high-speed video systems, coupled with precise anemometry, permit measures of high-speed aerial performance of birds in a natural state. We undertook the present study to test: (i) the manner in which barn swallows (Hirundo rustica) may exploit wind dynamics and ground effect while foraging and (ii) the relative importance of flapping versus gliding for accomplishing high-speed manoeuvers. Using multi-camera videography synchronized with wind-velocity measurements, we tracked coursing manoeuvers in pursuit of prey. Wind speed averaged 1.3–2.0 m s−1 across the atmospheric boundary layer, exhibiting a shear gradient greater than expected, with instantaneous speeds of 0.02–6.1 m s−1. While barn swallows tended to flap throughout turns, they exhibited reduced wingbeat frequency, relying on glides and partial bounds during maximal manoeuvers. Further, the birds capitalized on the near-earth wind speed gradient to gain kinetic and potential energy during both flapping and gliding turns; providing evidence that such behaviour is not limited to large, fixed-wing soaring seabirds and that exploitation of wind gradients by small aerial insectivores may be a significant aspect of their aeroecology.

既往关于燕类机动飞行的研究多聚焦于静风环境下的低速飞行与避障行为，但燕类实则依赖多风环境中的高速觅食活动得以生存。近年来，野外便携高速视频系统与高精度风速测量技术的进步，使得研究者得以在自然状态下量化鸟类的高速飞行性能。本研究旨在验证两项假设：其一，家燕（Hirundo rustica）在觅食过程中如何利用风场动力学与地面效应（ground effect）；其二，振翅飞行与滑翔在完成高速机动动作时的相对重要性。本研究采用多摄像头摄影系统与风速测量同步的实验方案，追踪了家燕捕猎猎物时的追踪机动行为。研究区域大气边界层内的平均风速为1.3~2.0 m s⁻¹，风切变梯度高于预期，瞬时风速范围为0.02~6.1 m s⁻¹。尽管家燕在常规转弯过程中通常会持续振翅，但在极限机动动作中，它们会降低振翅频率，转而依靠滑翔与半振翅模式完成动作。此外，家燕在振翅转弯与滑翔转弯过程中，均利用近地面风场梯度获取动能与势能；该研究结果表明，此类行为并非仅局限于大型固定翼翱翔海鸟，小型食虫飞行动物对风场梯度的利用，或许是其航空生态学（aeroecology）中的重要一环。