Smithsonian Conservation Biology Institute, Migratory Bird Center, National Zoological Park, Washington, DC 20008, USA.
Proc Biol Sci. 2011 Nov 22;278(1723):3437-43. doi: 10.1098/rspb.2011.0332. Epub 2011 Mar 30.
Climatic warming has intensified selection for earlier reproduction in many organisms, but potential constraints imposed by climate change outside the breeding period have received little attention. Migratory birds provide an ideal model for exploring such constraints because they face warming temperatures on temperate breeding grounds and declining rainfall on many tropical non-breeding areas. Here, we use longitudinal data on spring departure dates of American redstarts (Setophaga ruticilla) to show that annual variation in tropical rainfall and food resources are associated with marked change in the timing of spring departure of the same individuals among years. This finding challenges the idea that photoperiod alone regulates the onset of migration, providing evidence that intensifying drought in the tropical winter could hinder adaptive responses to climatic warming in the temperate zone.
气候变暖加剧了许多生物更早繁殖的选择，但气候变化对繁殖期以外的潜在限制因素却很少受到关注。候鸟为探索这种限制提供了一个理想的模型，因为它们在温带繁殖地面临变暖的温度，而在许多热带非繁殖地区面临降雨量下降的问题。在这里，我们使用美洲红雀（Setophaga ruticilla）春季出发日期的纵向数据表明，热带降雨和食物资源的年度变化与同一年中个体春季出发时间的明显变化有关。这一发现挑战了仅由光照时间调节迁徙开始的观点，提供了证据表明热带冬季干旱加剧可能会阻碍对温带气候变暖的适应性反应。
