School of Natural Sciences, Bangor University, Bangor, LL57 2UW, UK.
School of Life and Health Sciences, University of Roehampton, London, SW15 4JD, UK.
Sci Rep. 2024 Mar 27;14(1):7298. doi: 10.1038/s41598-024-56325-6.
A paradox of avian long-distance migrations is that birds must greatly increase their body mass prior to departure, yet this is presumed to substantially increase their energy cost of flight. However, here we show that when homing pigeons flying in a flock are loaded with ventrally located weight, both their heart rate and estimated energy expenditure rise by a remarkably small amount. The net effect is that costs per unit time increase only slightly and per unit mass they decrease. We suggest that this is because these homing flights are relatively fast, and consequently flight costs associated with increases in body parasite drag dominate over those of weight support, leading to an improvement in mass-specific flight economy. We propose that the relatively small absolute aerodynamic penalty for carrying enlarged fuel stores and flight muscles during fast flight has helped to select for the evolution of long-distance migration.
鸟类长途迁徙的一个悖论是，鸟类在出发前必须大大增加体重，但这被认为会大大增加飞行的能量成本。然而，在这里我们表明，当成群结队飞行的家鸽腹部负重时，它们的心率和估计的能量消耗仅会显著增加少量。净效应是单位时间内的成本仅略有增加，而单位质量的成本则下降。我们认为这是因为这些归巢飞行相对较快，因此与身体寄生虫阻力增加相关的飞行成本超过了重量支撑的成本，从而提高了每单位质量的飞行经济性。我们提出，在快速飞行过程中携带增大的燃料储存和飞行肌肉的相对较小的绝对空气动力惩罚有助于选择长途迁徙的进化。
