Pigeon racing is the sport of releasing specially trained homing pigeons, which then return to their homes over a carefully measured distance. The time it takes the animal to cover the specified distance is measured and the bird's rate of travel is calculated and compared with all of the other pigeons in the race to determine which animal returned at the highest speed. The sport achieved a great deal of popularity in Belgium in the mid-19th century. The pigeon fanciers of Belgium were so taken with the hobby that they began to develop pigeons specially cultivated for fast flight and long endurance called Voyageurs. From Belgium the modern version of the sport and the Voyageurs which the Flemish fanciers developed spread to most parts of the world.