Windscape and tortuosity shape the flight costs of northern gannets
Windscape and tortuosity shape the flight costs of northern gannets
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DOI：
10.1242/jeb.097915
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发表时间：
2014-03-01
影响因子：
2.8
通讯作者：
Gremillet, David
中科院分区：
文献类型：
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作者：
Amelineau, Francoise;Peron, Clara;Gremillet, David
当动物在景观中移动时，它们在具有高猎物密度的区域中的主动搜索阶段和朝向有利可图的摄食补丁的通勤阶段之间交替。这种主动的搜索运动比移动运动更曲折，而且据说更消耗能量。在这里，我们提供了一个经验验证这个长期的假设。为此，我们同时评估的能量消耗和轨迹在北方塘鹅（桑）使用GPS记录仪，潜水记录仪和三维加速度计。三种行为状态确定从GPS数据：觅食，当鸟类积极寻找猎物（高曲折，中速）;旅行，当鸟类通勤（直线轨迹，高速）;和休息（直线轨迹，低速）。从加速度数据计算的整体动态身体加速度被用作飞行期间能量消耗的代理。还测试了风景特征（风力和风向）对飞行成本的影响。能量消耗的北方塘鹅是更高的曲折觅食飞行期间比在更直线的旅行飞行，证明转弯确实是昂贵的。然而，风力和风向也强烈地影响了飞行能量消耗;在任何行为状态下，顺风飞行比逆风飞行成本更低，而强风飞行成本更低。尽管主要的飞行成本的风的行动，鸟类并没有完全优化其飞行轨迹相对于风向，可能是因为猎物分布相对于海岸线和风的可预测性。我们的研究说明了曲折度和风景如何塑造海洋捕食者（如北方塘鹅）的觅食成本。
When animals move across a landscape, they alternate between active searching phases in areas with high prey density and commuting phases towards and in-between profitable feeding patches. Such active searching movements are more sinuous than travelling movements, and supposedly more costly in energy. Here we provide an empirical validation of this long-lasting assumption. To this end, we evaluated simultaneously energy expenditure and trajectory in northern gannets (Morus bassanus) using GPS loggers, dive recorders and three-dimensional accelerometers. Three behavioural states were determined from GPS data: foraging, when birds actively searched for prey (high tortuosity, medium speed); travelling, when birds were commuting (straight trajectory, high speed); and resting (straight trajectory, low speed). Overall dynamic body acceleration, calculated from acceleration data, was used as a proxy for energy expenditure during flight. The impact of windscape characteristics (wind force and direction) upon flight costs was also tested. Energy expenditure of northern gannets was higher during sinuous foraging flight than during more rectilinear travelling flight, demonstrating that turns are indeed costly. Yet wind force and direction also strongly shaped flight energy expenditure; within any behavioural state it was less costly to fly with the wind than against it, and less costly to fly with strong winds. Despite the major flight costs of wind action, birds did not fully optimize their flight track relative to wind direction, probably because of prey distributions relative to the coastline and wind predictability. Our study illustrates how both tortuosity and windscape shape the foraging costs of marine predators such as northern gannets.