*Ecology and Conservation Science Division, Illinois Natural History Survey, Champaign-Urbana, IL 61820, USA; Division of Biological Sciences, 32 Campus Dr., University of Montana, Missoula, MT 59812, USA; Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA; Max Planck Institute for Ornithology, D-78315 Radolfzell, Germany.
Integr Comp Biol. 2008 Jul;48(1):134-51. doi: 10.1093/icb/icn044. Epub 2008 Jun 2.
Powered flapping flight has evolved independently in many different taxa. For flapping fliers, wingbeat parameters such as frequency and amplitude are the primary determinants of these animals' energetic expenditure during flight. Here we present data on wingbeat frequency and amplitude for three New World thrush species during 15 entire nocturnal migratory flights over the Midwestern United States. Using continuous (non-pulsing) radio transmitters, we were able to measure wingbeat frequency and relative amplitude of wingbeats as well as the characteristics of flap-pauses. Contrary to previous telemetric findings, all of the individuals we followed used both flapping-only and flap-pause flight. During migratory flights, wingbeat frequency, effective wingbeat frequency, and amplitude were highest during initial ascent. Effective wingbeat frequency and amplitude were lowest during final descent. We show that identification of species based solely on characteristics of the wingbeat e.g., during radar studies, can be difficult because variables such as wingbeat frequency and amplitude, wingbeat pausing, and pattern of beats and pauses vary between individuals of the same species and even within individual flights. We also show that observed wingbeat frequencies were lower than those predicted by theoretical models. We speculate that this may be because theoretical predictions are generally based on (1) data from larger birds and (2) data from diurnal flights. We found that diurnal wingbeat frequencies of thrushes were generally higher than were those during nocturnal migratory flight. Finally, we suggest that rather than remaining at a single altitude during flight or climbing slightly as theoretical models predict, thrushes often moved up and down in the air column, perhaps searching for favorable atmospheric conditions.
扑翼飞行在许多不同的分类群中独立进化。对于扑翼飞行者来说，翅膀拍打频率和幅度等翅膀参数是这些动物在飞行过程中能量消耗的主要决定因素。在这里，我们提供了三种新世界画眉在飞越美国中西部的 15 次整个夜间迁徙飞行过程中的翅膀拍打频率和幅度的数据。使用连续（非脉冲）无线电发射器，我们能够测量翅膀拍打频率和翅膀拍打幅度的相对幅度，以及拍打暂停的特征。与之前的遥测结果相反，我们跟踪的所有个体都使用了仅拍打和拍打暂停的飞行方式。在迁徙飞行中，翅膀拍打频率、有效翅膀拍打频率和幅度在初始上升阶段最高。在最后下降阶段，有效翅膀拍打频率和幅度最低。我们表明，仅根据翅膀拍打特征（例如在雷达研究中）来识别物种可能很困难，因为翅膀拍打频率和幅度、翅膀拍打暂停以及拍打和暂停模式等变量在同一物种的个体之间甚至在个体飞行中都有所不同。我们还表明，观察到的翅膀拍打频率低于理论模型预测的频率。我们推测，这可能是因为理论预测通常基于（1）来自较大鸟类的数据和（2）来自日间飞行的数据。我们发现，画眉的日间翅膀拍打频率通常高于夜间迁徙飞行时的频率。最后，我们建议，画眉在飞行过程中可能不会停留在单一高度，或者像理论模型预测的那样略微爬升，而是经常在空气柱中上下移动，也许是在寻找有利的大气条件。
