Umeyama Aika, Niizuma Yasuaki, Shirai Masaki
Laboratory of Environmental Zoology, Faculty of Agriculture, Meijo University, Nagoya, Aichi, Japan.
Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, Abiko, Chiba, Japan.
PeerJ. 2021 May 18;9:e11460. doi: 10.7717/peerj.11460. eCollection 2021.
Seabirds spend most of their lives at sea, except when visiting their breeding sites. Since the thermal conductivity of water is 25 times higher than that of air, seabirds resting on water lose heat and expend a considerable amount of energy for thermoregulation. For example, rhinoceros auklet (), a medium-sized (480620 g) alcid, spends most of its time floating on the sea. In order to estimate the cost of this behavior in terms of their daily energy expenditure (DEE), we studied rhinoceros auklets breeding on Teuri Island, Hokkaido Japan. We measured their resting metabolic rate (RMR) in air and on water by respirometry, and estimated their DEE by the doubly labeled water method. While RMR on water did not vary significantly between 10C and 15C, it was significantly higher at 5C. Air temperature (5.020.0C) had no effect on RMR. The DEE of free-ranging auklets averaged 1,005.5kJday (130.2, =3). Our results indicate that RMRs are elevated for auklets resting on water, particularly below their lower critical temperature (LCT), compared with in air. Accordingly, spending time above their LCT on water at any time of year will provide enhanced benefits, particularly to seabirds such as rhinoceros auklets which rest a considerable amount of time on water.
海鸟一生中的大部分时间都在海上度过，只有在前往繁殖地时除外。由于水的热导率比空气高25倍，栖息在水上的海鸟会散失热量，并消耗大量能量用于体温调节。例如，角嘴海雀（一种体重480 - 620克的中型海雀科鸟类）大部分时间都漂浮在海面上。为了根据它们的每日能量消耗（DEE）来估算这种行为的成本，我们研究了在日本北海道天卖岛繁殖的角嘴海雀。我们通过呼吸测量法测量了它们在空气中和水上的静息代谢率（RMR），并通过双标记水法估算了它们的DEE。虽然在10℃至15℃之间，水上的RMR没有显著变化，但在5℃时显著更高。气温（5.0 - 20.0℃）对RMR没有影响。自由活动的角嘴海雀的DEE平均为1005.5kJ/天（标准差为130.2，样本量n = 3）。我们的结果表明，与在空气中相比，栖息在水上的角嘴海雀的RMR会升高，尤其是在其下限临界温度（LCT）以下时。因此，一年中任何时候在水上停留高于其LCT的时间都会带来更大的益处，特别是对于像角嘴海雀这样在水上休息相当长时间的海鸟。
