Homing pigeon
Homing pigeons are called carrier pigeons when they are used to carry messages. This is possible where a message is written on thin light paper (such as cigarette paper) and rolled into a small tube attached to the bird's leg; this is called pigeon post. Pigeons can only go back to one "mentally marked" point that they have identified as their home. So "pigeon mail" can only work when the sender is actually holding the receiver's pigeons. White homing pigeons are used in Release Dove ceremonies at weddings, funerals, and some sporting events.