The impact of the physical environment on the foraging energetics of shearwaters and the consequences for breeding success

海洋环境中食物的分布和可得性随时间和空间的变化而变化很大。这对包括海鸟和海洋哺乳动物在内的海洋顶级捕食者构成了重大挑战，因为它们必须在寻找食物时采取有效的运动策略，同时在不断变化的风、浪和洋流中航行。然而，潮汐混合锋等海洋学特征提高了生产力，从而吸引了中上层和底层鱼类。因此，有一个强有力的联系之间的动态物理环境和可预测性的猎物组合。然而，物理环境对猎物在空间和时间上的分布的影响，以及随后对海洋顶级捕食者运动决策、能量成本和后代成功的影响，很少被研究。对于繁殖的海鸟来说，它们的小规模移动决定通常受到陆地殖民地位置的限制。这迫使它们定期在陆地殖民地和首选的近海觅食区之间的多变的风浪景观中航行，这些区域通常相隔数十至数百公里。在这样做的过程中，他们必须不断调整自己的行为与路线选择的后果，精力充沛的成本，和小鸡provisioning.Our项目将解开猎物的可用性，运动决策，飞行成本，和小鸡供应的物理环境的影响，使用案例研究涉及马恩岛剪水（Puffinus puffinus）繁殖在爱尔兰海的两个殖民地。马恩岛剪水繁殖的Bardsey岛和小牛的人饲料周围的潮汐混合前，即爱尔兰海锋（ISF）。马恩岛的剪水是熟练的飞行者，在这种情况下是一个很好的模式物种，因为它们利用强风和海浪进行低能量的翱翔，但在低风条件下必须更频繁地拍打翅膀，这在能量上更昂贵。已知来自两个研究种群的鸟类以ISF周围重叠的觅食区域为目标，但从相同风景的两侧进行操作，导致不同的能量后果和觅食策略。因此，风况的变化和海洋锋的维持对于供应和成功地饲养小鸡至关重要。我们将使用太阳能充电的GPS和加速度计标签，以及内置ECG（测量心率）的短期高分辨率加速度计标签，在两个繁殖季节监测马恩岛剪水的运动决策和飞行成本。加速度计提供三轴加速度数据，测量行为和翼振频率，这些数据可以转换为飞行成本的估计，沿着心率记录。将从整个研究区域提取精细尺度的环境数据，包括风和波浪，而海洋学模型将用于计算ISF在夏季的位置和强度。在夏季期间，将使用系泊回声测深仪监测中上层和底层猎物（如鲱鱼、鲱鱼、鳕鱼、鳕鱼）的可获性变化，同时将使用基于船舶的回声测深仪测量整个国际科学基金的空间猎物区。我们将在觅食之旅前后称量成年鸟和雏鸟的体重，以确定运动成本和觅食努力对成年鸟健康和雏鸟生长的影响。利用海洋风景、海洋变暖和分层的预测变化，我们将模拟持续气候变化对马恩岛海鸥运动成本和觅食成功率的影响。预测的减少风景和分层增加可能有不同的影响，繁殖马恩岛剪水的能源预算与人口持久性的后果。如果我们要了解未来气候变化对这些生态重要物种的影响，这个项目是至关重要的。

The distribution and availability of food in the marine environment is highly variable over space and time. This creates significant challenges for marine top predators, including seabirds and marine mammals, as they must deploy an efficient movement strategy in their search for food, while navigating an ever-changing landscape of winds, waves and ocean currents. However, oceanographic features, such as tidal mixing fronts enhance productivity, which in turn attracts pelagic and demersal fish. Thus, there is a strong linkage between the dynamic physical environment and the predictability of prey assemblages. Nevertheless, the influence of the physical environment on the distribution of prey in space and time, and the subsequent consequences for marine top predator movement decisions, energetic costs, and offspring success have rarely been studied on a day-by-day basis. For breeding seabirds, their fine-scale movement decisions are typically constrained by the location of terrestrial colonies. This forces them to regularly navigate the variable wind and wave landscape between the terrestrial colony and the preferred offshore foraging areas, often separated by tens to hundreds of kilometres. In doing so they must constantly adapt their behaviour with consequences for route choice, energetic costs, and chick provisioning.Our project will disentangle the effect of the physical environment on prey availability, movement decisions, flight costs, and chick provisioning using a case study involving Manx shearwaters (Puffinus puffinus) breeding on two colonies within the Irish Sea. Manx shearwaters breeding on Bardsey Island and the Calf of Man forage around a tidal mixing front, namely the Irish Sea Front (ISF). Manx shearwaters are adept fliers and an excellent model species in this context as they use strong winds and waves for low energy soaring but must beat their wings more frequently during low wind conditions, which is energetically more costly. Birds from the two study populations are known to target overlapping foraging areas around the ISF, but operate from opposite sides of the same windscape, resulting in different energetic consequences and foraging strategies. Therefore, variability in wind conditions and the maintenance of ocean fronts are critical to provisioning and successfully rearing chicks. We will monitor the movement decisions and flight costs of Manx shearwaters across two breeding seasons using solar charged GPS and accelerometer tags, and shorter-term high resolution accelerometer tags with inbuilt ECG (to measure heart rate). Accelerometers provide 3-axis acceleration data that measure behaviour and wingbeat frequency which can be converted into estimates of flight costs, along with records of heart rate. Fine scale environmental data will be extracted from across the study area, including wind and waves, while oceanographic models will be used to calculate the position and strength of the ISF over the course of the summers. Changes in the availability of pelagic and demersal prey (e.g. herring, sprat, cod, whiting) will be monitored using a moored echosounder over the course of the summer, while the spatial prey field across the ISF will be measured using ship based echosounder surveys. We will weigh adults and chicks before and after a foraging trip to determine the consequences of movement costs and foraging effort on adult fitness and chick growth.Using projected changes to the ocean windscape, ocean warming and stratification, we will model the consequences of continued climate change on Manx shearwater movement costs and foraging success. The predicted reduction in the windscape and increased stratification could have disparate effects on the energy budget of breeding Manx shearwaters with consequences for population persistence. This project is critical if we are to understand the impacts of future climate change on these ecologically important species.