1) Low-tech communication device 
The homing pigeon is a variety of domestic pigeon (Columba livia domestica) derived from the rock pigeon, selectively bred to find its way home over extremely long distances. The wild rock pigeon has an innate homing ability, meaning that it will generally return to its nest and mate. This made it relatively easy to breed from the birds that repea...
[n] - pigeon trained to return home
homer noun pigeon trained to return home
any pigeon used to carry messages and equipped by training and breeding to fly home, sometimes from great distances.