Data from: Homing pigeons respond to time-compensated solar cues even in sight of the loft

The sun has long been thought to guide bird navigation as the second step in a two-stage process, in which determining position using a map is followed by course setting using a compass, both over unfamiliar and familiar terrain. The animal's endogenous clock time-compensates the solar compass for the sun's apparent movement throughout the day, and this allows predictable deflections in orientation to test for the compass' influence using clock-shift manipulations. To examine the influence of the solar compass during a highly familiar navigational task, 24 clock-shifted homing pigeons were precision-tracked from a release site close to and in sight of their final goal, the colony loft. The resulting trajectories displayed significant partial deflection from the loft direction as predicted by either fast or slow clock-shift treatments. The partial deflection was also found to be stable along the entire trajectory indicating regular updating of orientation via input from the solar compass throughout the final approach flight to the loft. Our results demonstrate that time-compensated solar cues are deeply embedded in the way birds orient during homing flight, are accessed throughout the journey and on a remarkably fine-grained scale, and may be combined effectively simultaneously with direct guidance from familiar landmarks, even when birds are flying towards a directly visible goal.长期以来，学界普遍认为太阳是鸟类导航两阶段流程中的第二个环节：先通过地图感知完成位置确定，再借助罗盘（compass）设定飞行航向，该流程可适配陌生与熟悉两种地形。动物的内源生物钟（endogenous clock）会针对太阳全天的视运动，对太阳罗盘（solar compass）进行时间补偿，这使得通过时钟偏移操控（clock-shift manipulations）实验，可以定向诱导方位偏转，以此验证罗盘系统的导航作用。为探究太阳罗盘在高度熟悉的导航任务中的调控作用，研究人员对24只经时钟偏移处理的归巢鸽（homing pigeons）开展了精准轨迹追踪实验：放飞地点紧邻其最终目标——集群鸽舍（colony loft），且该目标处于放飞点的可视范围内。实验所得的飞行轨迹均出现了与鸽舍方向显著的部分偏转，这与快速或慢速时钟偏移处理的预测结果完全一致。研究同时发现，该方位偏转在整条轨迹中保持稳定，表明鸟类在最终飞抵鸽舍的进近飞行过程中，会持续通过太阳罗盘的输入信号定期更新自身飞行方位。本研究结果证实：经时间补偿的太阳方位线索深度嵌入鸟类归巢飞行的定向机制中，且会在整个旅程中以极高的精细度被调用；即便鸟类正飞向可视范围内的目标，该线索也可与熟悉地标提供的直接导航信息实现高效协同。