Cornell Laboratory of Ornithology, Cornell University, Ithaca, New York.
Glob Chang Biol. 2019 Feb;25(2):589-601. doi: 10.1111/gcb.14531. Epub 2018 Dec 9.
Current climate models and observations indicate that atmospheric circulation is being affected by global climate change. To assess how these changes may affect nocturnally migrating bird populations, we need to determine how current patterns of wind assistance at migration altitudes will be enhanced or reduced under future atmospheric conditions. Here, we use information compiled from 143 weather surveillance radars stations within the contiguous United States to estimate the daily altitude, density, and direction of nocturnal migration during the spring and autumn. We intersected this information with wind projections to estimate how wind assistance is expected to change during this century at current migration altitudes. The prevailing westerlies at midlatitudes are projected to increase in strength during spring migration and decrease in strength to a lesser degree during autumn migration. Southerly winds will increase in strength across the continent during both spring and autumn migration, with the strongest gains occurring in the center of the continent. Wind assistance is projected to increase across the central (0.44 m/s; 10.1%) and eastern portions of the continent (0.32 m/s; 9.6%) during spring migration, and wind assistance is projected to decrease within the central (0.32 m/s; 19.3%) and eastern portions of the continent (0.17 m/s; 6.6%) during autumn migration. Thus, across a broad portion of the continent where migration intensity is greatest, the efficiency of nocturnal migration is projected to increase in the spring and decrease in the autumn, potentially affecting time and energy expenditures for many migratory bird species. These findings highlight the importance of placing climate change projections within a relevant ecological context informed through empirical observations, and the need to consider the possibility that climate change may generate both positive and negative implications for natural systems.
当前的气候模型和观测结果表明，大气环流正在受到全球气候变化的影响。为了评估这些变化可能如何影响夜间迁徙鸟类的种群，我们需要确定在未来的大气条件下，迁徙高度的风助将会如何增强或减弱。在这里，我们利用来自美国大陆 143 个天气监测雷达站的数据，估算了春季和秋季夜间迁徙的每日高度、密度和方向。我们将这些信息与风的预测结果交叉，以估算在本世纪当前迁徙高度下，风助预计会如何变化。中纬度地区盛行的西风在春季迁徙期间预计会增强，在秋季迁徙期间则会适度减弱。整个大陆的南风在春季和秋季迁徙期间都将增强，其中大陆中心的增强幅度最大。预计在春季迁徙期间，大陆中部（0.44 m/s；10.1%）和东部地区（0.32 m/s；9.6%）的风助将会增加，而在秋季迁徙期间，大陆中部（0.32 m/s；19.3%）和东部地区（0.17 m/s；6.6%）的风助预计将会减少。因此，在大陆迁徙强度最大的广阔地区，夜间迁徙的效率预计将在春季增加，在秋季减少，这可能会影响许多候鸟物种的时间和能量消耗。这些发现突出了将气候变化预测置于通过实证观测获得的相关生态背景下的重要性，以及需要考虑到气候变化可能对自然系统产生积极和消极影响的可能性。
