One of our setters remembers his father asking this puzzle when he was a child. Perhaps there is a bit of a trick to it, but you have been warned.
A farmer sees five crows in a tree and, as it is lambing time, he raises his gun and shoots one of the crows. How many crows are left in the tree?
Of course there are four crows still alive, but none of these four birds will be in the tree; they will have all flown away, frightened by the noise of the gun.