“I bought a wooden whistle, but it wouldn’t whistle” is part of an old children’s song that goes on to joke about buying a metal whistle. But a modern metal whistle used by a policeman looks very ...

In many parts of Africa, humans cooperate with a species of wax-eating bird called the greater honeyguide, Indicator indicator, which leads them to wild bees' nests with a chattering call. By using ...