Department of Conservation Biology, Estación Biológica de Doñana-CSIC, Avenida Americo Vespucio, 41092 Seville, Spain.
Population Ecology Group, Institute for Mediterranean Studies (IMEDEA), CSIC-UIB, 07190 Esporles, Spain.
Nature. 2014 Nov 20;515(7527):410-3. doi: 10.1038/nature13696. Epub 2014 Sep 24.
Billions of organisms, from bacteria to humans, migrate each year and research on their migration biology is expanding rapidly through ever more sophisticated remote sensing technologies. However, little is known about how migratory performance develops through life for any organism. To date, age variation has been almost systematically simplified into a dichotomous comparison between recently born juveniles at their first migration versus adults of unknown age. These comparisons have regularly highlighted better migratory performance by adults compared with juveniles, but it is unknown whether such variation is gradual or abrupt and whether it is driven by improvements within the individual, by selective mortality of poor performers, or both. Here we exploit the opportunity offered by long-term monitoring of individuals through Global Positioning System (GPS) satellite tracking to combine within-individual and cross-sectional data on 364 migration episodes from 92 individuals of a raptorial bird, aged 1-27 years old. We show that the development of migratory behaviour follows a consistent trajectory, more gradual and prolonged than previously appreciated, and that this is promoted by both individual improvements and selective mortality, mainly operating in early life and during the pre-breeding migration. Individuals of different age used different travelling tactics and varied in their ability to exploit tailwinds or to cope with wind drift. All individuals seemed aligned along a race with their contemporary peers, whose outcome was largely determined by the ability to depart early, affecting their subsequent recruitment, reproduction and survival. Understanding how climate change and human action can affect the migration of younger animals may be the key to managing and forecasting the declines of many threatened migrants.
数十亿的生物，从细菌到人类，每年都在迁徙，通过越来越先进的遥感技术，它们的迁徙生物学研究正在迅速扩展。然而，对于任何生物体来说，它们的迁徙性能是如何随着生命的发展而发展的，人们知之甚少。迄今为止，年龄变化几乎总是被简化为最近出生的幼体在第一次迁徙时与未知年龄的成体之间的二分法比较。这些比较通常强调了成体比幼体具有更好的迁徙性能，但尚不清楚这种变化是渐进的还是突然的，是个体内部的改善、表现不佳者的选择性死亡，还是两者兼而有之。在这里，我们利用通过全球定位系统 (GPS) 卫星跟踪对个体进行长期监测所提供的机会，结合了 92 只猛禽个体的 364 次迁徙事件的个体内和横剖数据，这些个体的年龄为 1-27 岁。我们表明，迁徙行为的发展遵循一个一致的轨迹，比以前想象的更渐进和持久，这是个体内部改善和选择性死亡共同推动的，主要发生在生命早期和繁殖前迁徙期间。不同年龄的个体使用不同的迁徙策略，在利用顺风或应对风漂移的能力上也存在差异。所有的个体似乎都在与同代的同伴进行一场竞赛，其结果在很大程度上取决于它们能否及早出发，这影响了它们随后的招募、繁殖和生存。了解气候变化和人类活动如何影响年幼动物的迁徙，可能是管理和预测许多受威胁的迁徙者数量减少的关键。
