Despite the wealth of studies on seasonal movements of birds between southern nonbreeding locations and High Arctic breeding locations, the key mechanisms of navigation during these migrations remain elusive. A flight along the shortest possible route between pairs of points on a sphere (‘orthodrome’) requires a bird to be able to assess its current location in relation to its migration goal and to make continuous adjustment of heading to reach that goal. Alternatively, birds may navigate along a vector with a fixed orientation (‘loxodrome’) based on magnetic and/or celestial compass mechanisms. Compass navigation is considered especially challenging for summer migrations in Polar regions, as continuous daylight and complexity in the geomagnetic field may complicate the use of both celestial and magnetic compasses here. We examine the possible use of orientation mechanisms during migratory flights across the Greenland Icecap. Using a novel 2 g solar‐powered satellite transmitter, we documented the flight paths travelled by a female red knot Calidris canutus islandica during two northward and two southward migrations. The geometry of the paths suggests that red knots can migrate across the Greenland Icecap along the shortest‐, orthodrome‐like, path instead of the previously suggested loxodrome path. This particular bird's ability to return to locations visited in a previous year, together with its sudden course changes (which would be appropriate responses to ambient wind fields), suggest a map sense that enables red knots to determine location, so that they can tailor their route depending on local conditions.

中文翻译：

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红结如黑天鹅：一只鸟在重复穿越格陵兰冰盖时如何表现出导航能力

尽管对鸟类在南部非繁殖地和北极高地繁殖地之间的季节性运动进行了大量研究，但这些迁徙过程中的关键导航机制仍然难以捉摸。沿着球体上成对点之间的最短可能路线飞行（“正跑道”）要求鸟类能够评估与其迁徙目标相关的当前位置，并不断调整航向以达到该目标。或者，鸟类可以基于磁和/或天体罗盘机制沿着具有固定方向（'loxodrome'）的矢量导航。指南针导航被认为对于极地地区的夏季迁徙尤其具有挑战性，因为持续的日光和地磁场的复杂性可能会使这里的天文指南针和磁罗盘的使用复杂化。我们研究了在跨越格陵兰冰盖的迁徙飞行期间可能使用的定向机制。使用新型 2 g 太阳能卫星发射器，我们记录了雌性红结 Calidris canutus islandica 在两次向北和两次向南迁移期间的飞行路径。路径的几何形状表明，红节可以沿着最短的、类似正跑道的路径迁移穿过格陵兰冰盖，而不是之前建议的 loxodrome 路径。这种特殊的鸟能够返回前一年访问过​​的地点，再加上它突然的航向变化（这将是对环境风场的适当反应），这表明了一种地图感，使红节能够确定位置，以便它们可以定制它们的位置。路线视当地情况而定。