Department of Animal Ecology, Lund University, Ecology Building 22362, Lund, Sweden.
Biol Lett. 2010 Jun 23;6(3):297-300. doi: 10.1098/rsbl.2009.0785. Epub 2009 Dec 2.
We investigated the risk associated with crossing the Sahara Desert for migrating birds by evaluating more than 90 journeys across this desert by four species of raptors (osprey Pandion haliaetus, honey buzzard Pernis apivorus, marsh harrier Circus aeruginosus and Eurasian hobby Falco subbuteo) recorded by satellite telemetry. Forty per cent of the crossings included events of aberrant behaviours, such as abrupt course changes, slow travel speeds, interruptions, aborted crossings followed by retreats from the desert and failed crossings due to death, indicating difficulties for the migrants. The mortality during the Sahara crossing was 31 per cent per crossing attempt for juveniles (first autumn migration), compared with only 2 per cent for adults (autumn and spring combined). Mortality associated with the Sahara passage made up a substantial fraction (up to about half for juveniles) of the total annual mortality, demonstrating that this passage has a profound influence on survival and fitness of migrants. Aberrant behaviours resulted in late arrival at the breeding grounds and an increased probability of breeding failure (carry-over effects). This study also demonstrates that satellite tracking can be a powerful method to reveal when and where birds are exposed to enhanced risk and mortality during their annual cycles.
我们通过评估 4 种猛禽（鱼鹰 Pandion haliaetus、蜜鹰 Pernis apivorus、沼泽鹞 Circus aeruginosus 和欧亚红隼 Falco subbuteo）在撒哈拉沙漠迁徙时的 90 多次卫星追踪记录，研究了候鸟穿越撒哈拉沙漠的风险。40%的迁徙过程中出现了异常行为，如突然改变路线、缓慢飞行、中断、在沙漠中撤退以及因死亡而无法穿越等，这表明迁徙者遇到了困难。对于幼鸟（第一次秋季迁徙）来说，每次穿越撒哈拉沙漠的死亡率为 31%，而对于成年鸟（秋季和春季迁徙）来说，死亡率仅为 2%。与撒哈拉沙漠迁徙相关的死亡率占总年死亡率的很大一部分（对于幼鸟来说，最高可达一半），这表明这条迁徙路线对候鸟的生存和适应能力有深远的影响。异常行为导致候鸟到达繁殖地较晚，繁殖失败的概率增加（滞后效应）。本研究还表明，卫星追踪可以成为一种强大的方法，揭示鸟类在其年度迁徙过程中何时何地面临更高的风险和死亡率。
