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.

水生鸟类的体温调节（thermoregulation）成本高昂，换羽（moulting）期尤为如此，但目前鲜有针对水温对水生鸟类换羽策略影响的研究。本研究提出一般性假设：体温调节成本降低所节省的能量，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，在温水中换羽的水生鸟类会拥有更高的身体储备、更快的羽毛生长速率，且飞羽换羽（remigial moult）启动时间更早。本研究以大型海鸭普通绒鸭（Somateria mollissima dresseri）作为模式物种。在三年的实验周期内，对圈养个体分别进行温水（18 ℃）与冷水（8 ℃）处理，并在不同处理组间轮换个体。研究发现，两种水温处理下的羽毛生长速率并无显著差异；但与我们的预测相反，处于温水环境中的绒鸭体重更低，且其飞羽换羽启动时间相较于冷水组延迟了约7天。本研究数据表明，体重变化会以出乎意料的方式影响换羽时间，我们推测其可能通过激素级联反应调控飞羽换羽的发生。本研究强调了深化水温对水生鸟类飞羽换羽影响的认知的重要性，以便更好地评估全球变暖对其生存的潜在影响。