No one knows for certain how the arrangement works, but a certain species of woodpecker and tree ant are known to call temporary truces despite being mortal enemies most of the time. The southern rufous woodbecker and the black tree ant are normally predator and prey – but when the bird lays its eggs in the nest of the ants an agreement is made, a non-aggression pact of sorts, that protects the bird’s eggs from attacks by the nest and the ants’ nest from other birds while the chosen bird is nesting there.