which are only a few centimetres across. 而它们的巢窝相隔不过几厘米远

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
117. It's a remarkable skill and one we still do not fully understand.
     我们至今仍未能完全了解 这种了不起的本领
118. These birds are unusual for another reason.
     这些鸟之所以特别还有另外一个原因
119. Their little cup-like nests are made entirely from threads of saliva.
     它们小巧的杯状燕窝完全由唾液丝筑建

来自《行星地球 第一季 第四集 Planet Earth S01E04 洞穴》第 116 行