Guillemette Magella, Polymeropoulos Elias T, Portugal Steven J, Pelletier David
Departement de Biologie, Universite du Quebec a RimouskiRimouski, QC, Canada.
Institute for Marine and Antarctic Studies, University of TasmaniaHobart, TAS, Australia.
Front Physiol. 2017 Jul 25;8:532. doi: 10.3389/fphys.2017.00532. eCollection 2017.
The large amount of energy expended during flapping flight is associated with heat generated through the increased work of the flight muscles. This increased muscle work rate can manifest itself in core body temperature (T) increase of 1-2°C in birds during flight. Therefore, episodic body cooling may be mandatory in migratory birds. To elucidate the thermoregulatory strategy of a short-distance migrant, common eiders (), we implanted data loggers in the body cavity of wild birds for 1 year, and report information on T during their entire migration for 19 individuals. We show that the mean body temperature during flight (T) in the eiders was associated with rises in T ranging from 0.2 to 1.5°C, largely depending on flight duration. To understand how eiders are dealing with hyperthermia during migration, we first compare, at a daily scale, how T differs during migration using a before-after approach. Only a slight difference was found (0.05°C) between the after (40.30°C), the before (40.41°C) and the migration (40.36°C) periods, indicating that hyperthermia during flight had minimal impact at this time scale. Analyses at the scale of a flight cycle (flight plus stops on the water), however, clearly shows that eiders were closely regulating T during migration, as the relationship between the storage of heat during flight was highly correlated (slope = 1) with the level of heat dumping during stops, at both inter-individual and intra-individual levels. Because T at the start of a flight (T) was significantly and positively related to T at the end of a flight (T), and the maximal attained T during a flight (T), we conclude that in absence of sufficient body cooling during stopovers, eiders are likely to become increasingly hyperthermic during migration. Finally, we quantified the time spent cooling down during migration to be 36% of their daily (24 h) time budget, and conclude that behavioral body cooling in relation to hyperthermia represents an important time cost.
扑翼飞行过程中消耗的大量能量与飞行肌肉工作量增加所产生的热量有关。这种肌肉工作速率的增加在鸟类飞行过程中可表现为核心体温（T）升高1-2°C。因此，间歇性身体降温对于候鸟来说可能是必不可少的。为了阐明短距离迁徙鸟类普通绒鸭（）的体温调节策略，我们将数据记录器植入野生鸟类的体腔中达1年之久，并报告了19只个体在整个迁徙过程中的体温信息。我们发现，绒鸭飞行期间的平均体温（T）与0.2至1.5°C的体温升高有关，这在很大程度上取决于飞行持续时间。为了了解绒鸭在迁徙过程中如何应对体温过高问题，我们首先采用前后对比法，在每日尺度上比较迁徙期间体温（T）的差异。在迁徙后（40.30°C）、迁徙前（40.41°C）和迁徙期间（40.36°C）仅发现了微小差异（0.05°C），这表明在这个时间尺度上飞行期间的体温过高影响极小。然而，在飞行周期（飞行加水上停留）尺度上的分析清楚地表明，绒鸭在迁徙过程中密切调节体温，因为在个体间和个体内水平上，飞行期间的热量储存与停留期间的散热水平高度相关（斜率 = 1）。由于飞行开始时的体温（T）与飞行结束时的体温（T）以及飞行期间达到的最高体温（T）显著正相关，我们得出结论，在中途停留期间如果没有足够的身体降温，绒鸭在迁徙过程中可能会体温越来越高。最后，我们将迁徙期间用于降温的时间量化为其每日（24小时）时间预算的36%，并得出结论，与体温过高相关的行为性身体降温是一项重要的时间成本。
