MIGRATION BY SOARING OR FLAPPING FLIGHT IN BIRDS - THE RELATIVE IMPORTANCE OF ENERGY-COST AND SPEED
MIGRATION BY SOARING OR FLAPPING FLIGHT IN BIRDS - THE RELATIVE IMPORTANCE OF ENERGY-COST AND SPEED
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DOI：
10.1098/rstb.1993.0164
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发表时间：
1993-12-29
期刊：
影响因子：
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通讯作者：
HEDENSTROM, A
中科院分区：
文献类型：
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作者：
HEDENSTROM, A
在陆地上迁徙的鸟类使用两种基本飞行策略之一，即拍打或滑翔/腾空飞行。在高空飞行中，鸟类主要通过绕圈飞行，也就是上升的空气，然后滑行，直到遇到另一种热气流。动力扑翼飞行在能量上比滑翔飞行要昂贵得多。这给我们留下了一个问题，为什么大多数鸟类在迁徙时不采取腾飞的策略，而不是扑翼飞行？基于飞行力学理论，提出了(I)能量选择迁移和(Ii)时间选择迁移的优化准则，分别适用于扑翼飞行和俯冲飞行。这些指标是根据总体体型和高温条件下的爬升速度进行评估的。我还考虑了机翼形态和水平风的影响。总体结论是，将运输成本降至最低可能不是唯一的关键选择因素。在时间选择迁徙中，扑翼飞行比热腾飞更有利的鸟类的大小范围明显大于能量选择迁徙，这与在真实鸟类中发现的情况更一致。因此，由此产生的迁徙速度可能构成鸟类迁徙的一个重要选择力量。我还评估了混合策略的标准，即何时鸟类应该在有热能的情况下采用腾空飞行，而在其他情况下采用扑打飞行的方式。最后，我还讨论了一些可能影响迁徙策略演变的其他因素，如对侧风的敏感性、热力丰度和地形。
Birds migrating over land use either of two basic flight strategies, i.e. flapping or gliding/soaring flight. In soaring flight the birds gain altitude mainly by circling in thermals, i.e. rising air, and then they glide off until another thermal is encountered. Powered flapping flight is energetically much more expensive than gliding flight. This leaves us with the question why do not most birds adopt the soaring strategy rather than flapping flight on migration? I present optimization criteria, based on flight mechanical theory, for (i) energy-selected migration and (ii) time-selected migration, for flapping and soaring flight migration, respectively. These are evaluated in relation to general body size and rate of climb in thermals. I also consider the effects of wing morphology and horizontal winds. The general conclusion is that minimization of transport costs probably cannot be the only critical selective factor. In time-selected migration the size range of birds for which flapping flight is advantageous over thermal soaring flight, is significantly larger than in energy-selected migration, and this is in better agreement with what is found in real birds. Therefore, resulting migration speed probably constitutes an important selective force in bird migration. I also evaluate criteria for mixed strategies, i.e. when birds should use soaring flight when thermals are available and proceed by flapping flight otherwise. Finally, I also discuss some other factors, e.g. sensitivity to crosswinds, abundance of thermals and topography, which may affect the evolution of migration strategy.