Becciu Paolo, Troupin David, Dinevich Leonid, Leshem Yossi, Sapir Nir
Animal Flight Laboratory, Department of Evolutionary and Environmental Biology and Institute of Evolution, University of Haifa, 199 Aba Khoushy Ave. Mount Carmel, 3498838, Haifa, Israel.
Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
Mov Ecol. 2023 Jul 27;11(1):44. doi: 10.1186/s40462-023-00402-4.
Millions of birds travel every year between Europe and Africa detouring ecological barriers and funnelling through migratory corridors where they face variable weather conditions. Little is known regarding the response of migrating birds to mesoscale meteorological processes during flight. Specifically, sea-breeze has a daily cycle that may directly influence the flight of diurnal migrants.
We collected radar tracks of soaring migrants using modified weather radar in Latrun, central Israel, in 7 autumns between 2005 and 2016. We investigated how migrating soaring birds adjusted their flight speed and direction under the effects of daily sea-breeze circulation. We analysed the effects of wind on bird groundspeed, airspeed and the lateral component of the airspeed as a function of time of day using Generalized Additive Mixed Models. To identify when birds adjusted their response to the wind over time, we estimated first derivatives.
Using data collected during a total of 148 days, we characterised the diel dynamics of horizontal wind flow relative to the migration goal, finding a consistent rotational movement of the wind blowing towards the East (morning) and to the South-East (late afternoon), with highest crosswind speed around mid-day and increasing tailwinds towards late afternoon. Airspeed of radar detected birds decreased consistently with increasing tailwind and decreasing crosswinds from early afternoon, resulting in rather stable groundspeed of 16-17 m/s. In addition, birds fully compensated for lateral drift when crosswinds were at their maximum and slightly drifted with the wind when crosswinds decreased and tailwinds became more intense.
Using a simple and broadly applicable statistical method, we studied how wind influences bird flight through speed adjustments over time, providing new insights regarding the flexible behavioural responses of soaring birds to wind conditions. These adjustments allowed the birds to compensate for lateral drift under crosswind and reduced their airspeed under tailwind. Our work enhances our understanding of how migrating birds respond to changing wind conditions during their long-distance journeys through migratory corridors.
每年有数以百万计的鸟类往返于欧洲和非洲之间，它们绕过生态屏障，通过迁徙通道飞行，在那里它们面临着多变的天气条件。关于候鸟在飞行过程中对中尺度气象过程的反应，我们所知甚少。具体而言，海风具有日循环，可能直接影响昼行性候鸟的飞行。
2005年至2016年期间的7个秋季，我们在以色列中部拉特伦使用改良型气象雷达收集了翱翔候鸟的雷达轨迹。我们研究了翱翔候鸟在每日海风环流的影响下如何调整飞行速度和方向。我们使用广义相加混合模型分析了风对鸟类地速、空速和空速横向分量随时间的影响。为了确定鸟类何时随着时间推移调整对风的反应，我们估计了一阶导数。
利用总共148天收集的数据，我们描绘了相对于迁徙目标的水平风流的昼夜动态，发现风向东（早晨）和向东南（傍晚）吹的一致旋转运动，中午左右侧风速度最高，傍晚时分顺风增加。从午后早些时候开始，雷达探测到的鸟类空速随着顺风增加和侧风减少而持续下降，导致地速相当稳定，为16-17米/秒。此外，当侧风最大时，鸟类完全补偿了横向漂移，当侧风减少且顺风变得更强时，鸟类会随风略有漂移。
我们使用一种简单且广泛适用的统计方法，研究了风如何通过随时间的速度调整影响鸟类飞行，为翱翔鸟类对风况的灵活行为反应提供了新的见解。这些调整使鸟类能够在侧风下补偿横向漂移，并在顺风下降低空速。我们的工作增进了我们对候鸟在通过迁徙通道进行长途旅行期间如何应对不断变化的风况的理解。
