Like bats they use echolocation to navigate. 和蝙蝠一样 它们也利用回声定位来导航

110. Returning from hunting in the sunlight
     完成白天的狩猎工作后
111. these commuters rely on their loud clicks to find their way through the cave passages in total darkness.
     这些住客利用它们响亮的叫声 在漆黑一片的洞穴通道内辨别方向
112. They're cave swiftlets.
     它们就是洞金丝燕
113. Like bats they use echolocation to navigate.
     和蝙蝠一样 它们也利用回声定位来导航
114. We need lights to see what's going on,
     我们必须有光才能看清前方的路
115. but in the pitch black the swiftlets manage unerringly to locate their individual nesting sites,
     但是金丝燕却能在黑暗中 准确无误地到达自己的筑巢点
116. which are only a few centimetres across.
     而它们的巢窝相隔不过几厘米远

来自《行星地球 第一季 第四集 Planet Earth S01E04 洞穴》第 113 行