Biological Station Rybachy, Zoological Institute of the Russian Academy of Sciences, 238535 Rybachy, Kaliningrad Region, Russia; Department Vertebrate Zoology, St. Petersburg State University, 199034 St. Petersburg, Russia; Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 194223 St. Petersburg, Russia.
Biological Station Rybachy, Zoological Institute of the Russian Academy of Sciences, 238535 Rybachy, Kaliningrad Region, Russia; Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 194223 St. Petersburg, Russia.
Curr Biol. 2017 Sep 11;27(17):2647-2651.e2. doi: 10.1016/j.cub.2017.07.024. Epub 2017 Aug 17.
The longitude problem (determining east-west position) is a classical problem in human sea navigation. Prior to the use of GPS satellites, extraordinarily accurate clocks measuring the difference between local time and a fixed reference (e.g., GMT) [1] were needed to determine longitude. Birds do not appear to possess a time-difference clock sense [2]. Nevertheless, experienced night-migratory songbirds can correct for east-west displacements to unknown locations [3-9]. Consequently, migratory birds must solve the longitude problem in a different way, but how they do so has remained a scientific mystery [10]. We suggest that experienced adult Eurasian reed warblers (Acrocephalus scirpaceus) can use magnetic declination to solve the longitude problem at least under some circumstances under clear skies. Experienced migrants tested during autumn migration in Rybachy, Russia, were exposed to an 8.5° change in declination while all other cues remained unchanged. This corresponds to a virtual magnetic displacement to Scotland if and only if magnetic declination is a part of their map. The adult migrants responded by changing their heading by 151° from WSW to ESE, consistent with compensation for the virtual magnetic displacement. Juvenile migrants that had not yet established a navigational map also oriented WSW at the capture site but became randomly oriented when the magnetic declination was shifted 8.5°. In combination with latitudinal cues, which birds are known to detect and use [10-12], magnetic declination could provide the mostly east-west component for a true bi-coordinate navigation system under clear skies for experienced migratory birds in some areas of the globe.
经度问题（确定东西位置）是人类海上航行的一个经典问题。在使用 GPS 卫星之前，需要使用极其精确的时钟来测量当地时间与固定参考时间（例如格林威治标准时间）之间的差异，以确定经度。鸟类似乎没有时差感[2]。然而，有经验的夜间迁徙鸣禽可以纠正未知位置的东西位移[3-9]。因此，候鸟必须以不同的方式解决经度问题，但它们是如何做到的仍然是一个科学谜[10]。我们认为，有经验的成年欧亚芦苇莺（Acrocephalus scirpaceus）至少在某些情况下，可以在晴朗的天空中利用磁偏角来解决经度问题。在俄罗斯Rybachy 进行秋季迁徙期间测试的有经验的候鸟，暴露在 8.5°的磁偏角变化下，而所有其他线索保持不变。如果磁偏角是它们地图的一部分，这相当于虚拟的磁位移到苏格兰。成年候鸟通过将它们的航向从 WSW 改变到 ESE 来做出反应，与补偿虚拟磁位移一致。尚未建立导航地图的幼鸟在捕获地点也朝向 WSW，但当磁偏角变化 8.5°时，它们变得随机定向。结合鸟类已知可以检测和利用的纬度线索[10-12]，在某些地区的晴朗天空下，磁偏角可以为有经验的候鸟提供真正的双坐标导航系统的大部分东西向分量。
