The language of birds: 4. Birds that talk to themselves
There are a few species of bird, breeding in the total darkness of large caves, that use sounds not for communication but to "see in the dark" so to speak. Like many bats, these creatures "echo-locate". As such they are not strictly relevant to a discussion of bird language, except that they could be said to be talking to themselves. As is well-known in bats, a short sharp sound is created by the bird, the echo is then listened to, the time gap assessed and an appropriate response made, e.g. turning left if you are about to collide with a stalagtite. One such feathered echo-locator is the oilbird Steatornis caripensis of north-eastern South America, a large nightjar - like bird that feeds at night on fruit. The others are certain species of swiftlet from the Oriental and Australasian zoogeographical regions. They are the birds whose nests are used for soup, the best-known species and colony being the black-nest swiftlet Collocalia maxima of the Great Niah caves in Sarawak (Borneo).
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