Bishop Charles M, Halsey Lewis G, Askew Graham N
School of Environmental and Natural Sciences, Bangor University, Bangor, Gwynedd, UK.
School of Life and Health Sciences, University of Roehampton, London, UK.
Biol Lett. 2025 Jul;21(7):20250031. doi: 10.1098/rsbl.2025.0031. Epub 2025 Jul 9.
The energy expended by animals during locomotion is often of considerable ecological importance. However, inaccurate conclusions about energy expenditure may arise if the limitations of the proxy variables being used to infer locomotion costs are not considered. The study of 'cluster' flocking behaviour in pigeons, using wingbeat frequency as a proxy for mechanical energy output, provides a useful illustration of these pitfalls. In contrast to claims in the literature, we suggest that published body kinematic values measured with accelerometers, along with our own heart rate data, show little evidence in support of the hypothesis that there is an increase in the mechanical energy costs for most pigeons to fly in a typical 'cluster' flock. Indeed, our re-analyses of acceleration-based measures of body power suggest there may be a positive energetic advantage to flying at low flock densities. We suggest that, when assessing energy expenditure using accelerometry-derived variables, the energy proxy units should be consistent with those of power, whether mass specific or absolute, and should control for differences in body mass and speed where appropriate. Accumulated total journey costs should also be assessed alongside instantaneous costs, with the former likely to be at least as ecologically significant.
动物在运动过程中消耗的能量通常具有相当重要的生态意义。然而，如果不考虑用于推断运动成本的替代变量的局限性，可能会得出关于能量消耗的不准确结论。以振翅频率作为机械能输出的替代指标，对鸽子“集群”飞行行为的研究，很好地说明了这些陷阱。与文献中的说法相反，我们认为，已发表的用加速度计测量的身体运动学数值，以及我们自己的心率数据，几乎没有证据支持这样的假设，即大多数鸽子在典型的“集群”飞行中机械能成本会增加。事实上，我们对基于加速度的身体功率测量值的重新分析表明，在低密度鸟群中飞行可能具有积极的能量优势。我们建议，在使用加速度计得出的变量评估能量消耗时，能量替代单位应与功率单位一致，无论是比质量功率还是绝对功率，并应在适当情况下控制体重和速度的差异。累积的总行程成本也应与瞬时成本一起评估，前者可能至少具有同样重要的生态意义。
