听力原文

As the water level falls, birds begin to gather. Herons, egrets and cormorants mingle with a far rarer visitor, the black-faced spoonbill.
随着水位下降，鸟儿们开始聚集。苍鹭、白鹭和鸬鹚和另一种稀有的动物混在一起，这就是黑脸琵鹭。
These endangered migrants have travelled the length of the Chinese coastline from Northern China and Korea.
这些濒危的候鸟们从中国北部和朝鲜半岛沿着中国的海岸线一路飞来
Mai Po marks the end of a 2,000-kilometre journey during which the birds may have lost up to a third of their body weight.
米埔标志着这长达2000多公里旅途的结束。鸟儿在飞行中甚至可能消耗掉体重的三分之一。
Four hundred black-faced spoonbills, a quarter of the world's population, pass the winter here.
占了世界数量四分之一的400多只黑脸琵鹭会在这里过冬
At low water, trapped shrimps and fish become easy prey, a life saver for these endangered birds.
在浅水中被困的鱼虾易于捕食，成为了这些濒危鸟儿们的救命粮草。

重点讲解

重点讲解：
1. begin to do sth.
开始；着手做某事；
eg. We begin to plumb the mysteries of the universe.
我们开始探索宇宙的奥秘。
eg. When the aims of the partners begin to diverge, there'strouble.
当合作伙伴的目标开始出现分歧时，麻烦就产生了。
2. up to
高达；多达；
eg. They have to walk sometimes up to two hours to come to work and usually go without lunch to save money.
他们有时需要步行多达两小时来上班，并通常为了省钱不吃午饭。
eg. Up to half of current users will eventually die of a tobacco-related disease.
当前使用者中多达半数最终将死于某种烟草相关疾病。
3. 分数的表达方式
分数在英语中通常是借助于基数词和序数词来共同表达的。其中基数词表示分子，序数词表示分母；
eg. The centimeter is one-tenth of the decimeter or one-hundredth of the meter．
厘米是分米的十分之一，或者说是米的百分之一。
eg. However，the number of boys will bea third or less than the girls in the class．
但是，班里男生的人数将比女生少三分之一或更少。