this is a desperate race against worsening weather. 这是一场与恶劣气候的死亡赛跑

308. But even a young crane is a heavy prize
     一只小鹤的份量也是挺重的
309. and the eagle has to struggle to control it.
     金雕不得不努力控制飞行
310. The mother can wait no longer -
     母鹤可不能等得太久
311. this is a desperate race against worsening weather.
     这是一场与恶劣气候的死亡赛跑
312. The rest of the flock battle on.
     鹤群其它成员开始背水一战
313. In the ascent every wing beat becomes an exhausting struggle.
     上升过程中每扇一下翅膀 都得用尽全身气力
314. At last they are over the highest barrier that lies in their way.
     最后它们终于翻越了旅途中最高的障碍

来自《行星地球 第一季 第二集 Planet Earth S01E02 山地》第 311 行