By the time it fledges, the Pisonia seeds will have dispersed 等它羽翼丰满之时 腺果藤树种子已经传播完毕

230. The fairy tern laid another egg,
     白燕鸥又下了一颗蛋
231. and now she has a tiny chick to feed.
     现在她要养一只小鸟了
232. This chick is lucky.
     这只小鸟很幸运
233. By the time it fledges, the Pisonia seeds will have dispersed
     等它羽翼丰满之时 腺果藤树种子已经传播完毕
234. and the danger they brought will be gone.
     它们带来的危险也将不复存在
235. Even the most idyllic looking of islands
     再诗情画意的岛屿
236. presents challenges for the animals living there.
     岛上的动物也要面临挑战

来自《行星地球 第二季 第一集 Planet Earth S02E01 岛屿》第 233 行