Heterothermy and torpor as energy saving strategies in Antarctic storm-petrel nestlings

威尔逊风暴海燕是南极最小的恒温动物。考虑到它们的体积小，因此能量储存能力有限，威尔逊风暴海燕需要使用有效的策略来应对可预测和不可预测的食物短缺。在该物种的繁殖季节内和繁殖季节之间观察到食物供应的剧烈波动。在本研究中，我们旨在研究威尔逊风暴海燕雏鸟如何将异温作为一种生理策略来优化能量投资和冬眠作为一种策略，以确保在不可预测的食物短缺中生存。我们将测试雏鸟的营养状况如何决定体温和静息代谢率，以及这是否受到环境温度的调节。为了适应可预测的食物供应差异，我们将研究体温和静息代谢率的日常节律。我们将测试威尔逊风暴海燕雏鸟是否会在白天成年鸟不能提供食物时策略性地下调体温和静息代谢率。我们将进一步研究雏鸟异温性个体差异的原因和后果。我们预计，在父母较少喂养的雏鸡中，与体温降低和更多地使用麻木有关的身体功能受损，如生长和免疫投入。因此，威尔逊风暴海燕雏鸟的异温性可能通过减少能量消耗和投资于最终决定生存和繁殖机会的身体功能之间的权衡而产生健康结果。作为对可预测的食物供应差异的适应，我们将研究在恶劣天气事件（如暴风雪）中小鸡的异温性，预计这些天气事件将变得更加频繁，并经常导致巢堵塞。因此，这项研究对该物种适应气候变化具有影响，既涉及食物供应减少，特别是南极磷虾种群减少，也涉及暴风雪频率增加。

Wilsons storm petrels Oceanites oceanicus are the smallest endotherm breeding in the Antarctic. Given their small size and thus limited energy storage capacities, Wilsons storm petrels need to use efficient strategies to cope with both predictable and unpredictable food shortages. Strong fluctuations in food availability have been observed both within and among breeding seasons in this species. In the present study, we aim to study how Wilsons storm-petrel nestlings use heterothermy as a physiological strategy to optimize energetic investment and torpor as a strategy to ensure survival during unpredictable food shortages. We will test how body temperature and resting metabolic rate are determined by the nutritional state of nestlings, and if this is modulated by ambient temperature. As an adaptation to predictable differences in food availability, we will study daily rhythms of body temperature and resting metabolic rate. We will test if Wilsons storm-petrel nestlings strategically down-regulate their body temperature and resting metabolic rate during daytime when adults cannot deliver food. We will further study causes and consequences of individual differences in heterothermy of nestlings. We expect compromised body functions such as growth and investment into immunology in relation to decreased body temperatures and more use of torpor in chicks provisioned less frequently by their parents. Thus, heterothermy in Wilsons storm-petrel chicks may have fitness consequences through a trade-off between reducing energetic costs and investing in body functions which ultimately determine the chances for survival to breeding. As an adaptation to predictable differences in food availability, we will study heterothermy of chicks during severe weather events such as snow storms, which are predicted to become more frequent and often result in blocking of nests. The study therefore has implications for the adaptation of the species to climate change, both in relation to reduced food availability, especially reduced stocks of Antarctic krill, and increased snow storm frequencies.