原文视听

A clue tothe source ofthe guano can be heard above the noise of the river.
鸟粪的源头能听到河水上空的鸟鸣
The sound originateshigh upin the roof of the cave.
噪音因为山洞而被放大
The entrance isfull of swifts.
入口处聚满了雨燕
They are very sociable birds,
他们是社交性动物
more than 200,000 of them share this cave in southern Guizhou province.
约200000多的共享贵州南部的洞穴
The biggest swift colony in China.
中国最大的雨燕栖息地
These days, Chinese house swifts mostly nest in the roofs of buildings,
如今 中国的家燕多数将巢穴建在建筑物的屋顶
but rock crevasses like these were their original home
但其实在房屋被发明出来之前
long before houses were invented
这样的岩缝才是他们原本安家的地方
Though the swifts depend on the cave for shelter,
尽管雨燕依靠洞穴遮蔽
they never stray further thanthe limits ofdaylight
他们却必定在日落前归巢
as their eyes can't see in dark.
因为他们的眼睛无法在黑夜中看清事物
However, deep inside the cavern
然而洞穴深处
are the creatures are better equipped
是一群更适应地下
for subterranean life.
隐秘生活的居民
A colony of bats is just waking up,
一群蝙蝠刚刚醒来
usingultrasonic squeaksto orientate themselves in the darkness.
他们运用超声波在黑夜中确定自己的方位
Night is the time to go hunting.
夜晚是狩猎时间

重点解释

妙语佳句:

the source of:...的来源

Where is the source of the Rhine?

莱茵河发源于何处？

high up:位置高

A lark was singing high up in the sky.

一只云雀在高空中歌唱。

full of:充满 ...

His songs are full of dirge.

他的歌充满了忧伤。

swift colondy:雨燕

long before:在很久以前

It was not long before tragedy struck again.

没多久，灾难又再次降临。

limit of:...的限期

She has reached the limit of her patience.

她已到了忍无可忍的地步。

ultrasonic squeak:超声波

This moth's ear is tuned in to the bat's ultrasonic squeak

这种蛾的耳朵能收听到蝙蝠的超音速的尖叫声。

in the darkness:在黑暗中

A little lantern blinked in the darkness.

一盏小灯笼在黑暗中微微闪光。

剧情常识:
第四集《风雪塞外》

　　该集所涉及的地域样貌是系列中最多样化最丰富的。有内蒙草原、甘肃戈壁，也有东北密林、西部边陲。有以“魔鬼城”闻名的敦煌雅丹，也有凡间仙境长白山天池，有硕果累累的吐鲁番，也有荒芜人迹的大沙漠。这里生活着野马、野猪、鹅喉羚、沙鼠、大天鹅、蓑羽鹤、沙狐和东北虎，还有驯金雕捕猎的哈萨克族，用传统方法破冰捕鱼的赫哲族，养蚕织成五彩丝绸的维吾尔族，豢养驯鹿作为交通工具的鄂温克族，当然更少不了生活在马背上的蒙古族。该集有很大一部分表现了动物与少数民族生活之间的密切联系。这种关系由来已久，甚至敦煌壁画里也有关于驼队的生动描绘。

考考你:

如今中国的家燕多数将巢穴建在建筑物的屋顶。

夜晚是狩猎时间。

上期答案：http://www.kekenet.com/menu/201207/190619.shtml
The people who live here are among the poorest in China.
In neighboring Yunnan province limestone rocks have taken over entirely.