- which are only a few centimetres across.
而它们的巢窝相隔不过几厘米远 - 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 - These birds are unusual for another reason.
这些鸟之所以特别还有另外一个原因 - 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 - It takes more than 30 days to complete one.
每个燕窝得花上30多天才能完工 - The nests are very precious objects,
燕窝是非常珍贵的东西 - and not only for the birds.
不仅只是针对这些鸟而言