Data from: Does water temperature affect the timing and duration of remigial moult in sea ducks? An experimental approach

Aquatic birds have high cost of thermoregulation, especially during the moulting period, yet the effect of water temperature on the moulting strategy of aquatic birds has rarely been studied. Our general hypothesis is that energy savings associated with lower thermoregulation costs would be allocated to moulting processes. We predicted that aquatic birds moulting in warm water would have a higher level of body reserves, a faster growth rate of feathers, and an earlier remigial moult onset compared with birds moulting in cold water. We used the common eider (Somateria mollissima dresseri), a large sea duck, as the model species. Captive individuals were experimentally exposed to warm (18 °C) and cold (8 °C) water treatments during a three year period with individuals swapped between treatments. We found a similar feather growth rate for the two water temperature treatments and in contrast to our predictions, eiders exposed to warm water had a lower body mass and showed a delayed onset of remigial moult of approximately 7 days compared with those exposed to cold water. Our data indicate that body mass variations influence the timing of moult in unexpected ways and we suggest that it likely controls the occurrence of wing moult through a hormonal cascade. This study emphasizes the importance of improving our knowledge of the effects of water temperature on remigial moult of aquatic birds, to better assert the potential effects of global warming on their survival.水禽的体温调节（thermoregulation）成本高昂，尤其在换羽期（moulting period），但目前针对水温对水禽换羽策略影响的研究仍较为匮乏。本研究提出一般性假说：较低体温调节成本所节省的能量，将被分配至换羽过程中。我们预测，相较于在冷水中换羽的个体，在温暖水域换羽的水禽将拥有更高的体储备、更快的羽毛生长速率，且飞羽换羽（remigial moult）的起始时间更早。本研究以大型海鸭——普通绒鸭（Somateria mollissima dresseri）作为模式物种。在为期三年的实验周期内，对圈养个体分别施加18℃温水与8℃冷水两种水温处理，并在处理组间轮换实验个体。研究结果显示，两种水温处理下的羽毛生长速率并无显著差异；且与预测结果相反，暴露于温水环境的普通绒鸭体质量更低，其飞羽换羽起始时间较冷水组个体延迟约7天。数据分析表明，体质量变化以出乎预料的方式影响换羽时序，我们推测其可能通过激素级联反应（hormonal cascade）调控翅羽换羽的发生。本研究强调，深化对水温影响水禽飞羽换羽机制的认知，有助于更准确地评估全球变暖（global warming）对水禽生存的潜在影响。