Data from: The cost of migration: spoonbills suffer higher mortality during longer spring migrations

Explanations for the wide variety of seasonal migration patterns of animals all carry the assumption that migration is costly and that this cost increases with migration distance. Although in some studies the relationships between migration distance and breeding success or annual survival are established, none have investigated whether mortality during the actual migration increases with migration distance. Here we compared seasonal survival between Eurasian spoonbills that breed in The Netherlands and migrate different distances (c. 1,000 km, 2,000 km and 4,500 km) to winter in France, Iberia or Mauritania. On the basis of resightings of individually marked birds throughout the year between 2005 and 2012, we show that summer, autumn and winter survival were very high and independent of migration distance, whereas mortality during spring migration was much higher (18%) for the birds that wintered in Mauritania, compared to those flying only as far as France (5%) or Iberia (6%). As such, this study is the first to show empirical evidence for increased mortality during longer migrations.学界对动物多种多样的季节性迁徙模式所提出的各类解释，均默认迁徙存在成本，且该成本随迁徙距离增加而升高。尽管部分研究已确立了迁徙距离与繁殖成功率或年存活率之间的关联，但尚无研究探究实际迁徙过程中的死亡率是否随迁徙距离增加而升高。本研究以在荷兰繁殖的欧亚琵鹭（Eurasian spoonbill）为对象，对比了它们分别迁徙约1000公里、2000公里、4500公里至法国、伊比利亚半岛或毛里塔尼亚越冬时的季节性存活率差异。基于2005年至2012年全年对个体标记鸟类的重见记录，本研究发现：夏季、秋季和冬季的存活率均处于较高水平，且与迁徙距离无关；但相较仅迁徙至法国（5%）或伊比利亚半岛（6%）越冬的个体，在毛里塔尼亚越冬的个体其春季迁徙期间的死亡率显著更高（18%）。综上，本研究首次为"更长距离迁徙会导致死亡率升高"提供了实证依据。