The domestic pigeon (Columba livia domestica ) is a pigeon subspecies that was derived from the rock dove (also called the rock pigeon). The rock pigeon is the world's oldest domesticated bird. Mesopotamian cuneiform tablets mention the domestication of pigeons more than 5,000 years ago, as do Egyptian hieroglyphics. Research suggests that domestication of pigeons occurred as early as 10,000 years ago.
Pigeons have made contributions of considerable importance to humanity, especially in times of war. In war the homing ability of pigeons has been put to use by making them messengers. So-called war pigeons have carried many vital messages and some have been decorated for their services. Medals such as the Croix de Guerre, awarded to Cher Ami, and the Dickin Medal awarded to the pigeons G.I. Joe and Paddy, amongst 32 others, have been awarded to pigeons for their services in saving human lives.
Despite this, city pigeons today are seen as pests, mainly due to their droppings. Feral pigeons are considered invasive in many parts of the world, though they have a positive impact on wild bird populations, serving as an important prey species of birds of prey.
Pigeons bred for meat are generally called squab and harvested from young birds. Pigeons grow to a very large size in the nest before they are fledged and able to fly, and in this stage of their development (when they are called squabs) they are prized as food. For commercial meat production a breed of large white pigeon, the King pigeon, has been developed by selective breeding. Breeds of pigeons developed for their meat are collectively known as utility pigeons.
Domestic pigeons reproduce exactly as wild rock pigeons, but may include human interventions. Generally humans will select breeding partners. Crop milk or pigeon milk produced by both male and female parent birds may occasionally be replaced with artificial substitutes. Pigeons are extremely protective of their eggs, and in some cases will go to severe lengths to protect their productive eggs and have been known to seek revenge on those who interfere with their productive process. Baby pigeons are called squeakers or squabs.
Pigeons have served key roles as food, pets, holy animals, post carriers, and more for thousands of years. The earliest record mention of pigeons comes from Mesopotamia some 5,000 years ago. Ancient Egyptians kept vast quantities of them, and would sacrifice tens of thousands at a time for ritual purposes. Akbar the Great travelled with a coterie of thousands of pigeons. They were introduced to the Americas about 400 years ago, as they were not native to the New World. Around the 18th century, interest in fancy pigeons began, and breeders greatly expanded the variety of pigeons.
Despite the long history of pigeons, little is known about their initial domestication. Which subspecies of C. livia was the progenitor of domestics, exactly when, how many times, where and how they were domesticated, and how they spread, remains unknown. Their fragile bones, and similarity to wild birds makes the fossil record a poor tool for their study. Thus, most of what is known comes from written accounts, which almost certainly do not cover the first stages of domestication. Because domestic and feral pigeons have extensively interbred with wild pigeons, wild-type pigeons may not truly exist anymore, or are nearly extinct. This frequent breeding further muddies the true origins of pigeons.
From a genetic perspective, there are two loose ancestral clades of pigeons, but there is striking genetic homogeneity due to frequent interbreeding and human directed cross-breeding. The first ancestral clade contains pigeons with exaggerated crops, tails, manes; the second contains tumblers (the most diverse group), homing pigeons, owl pigeons, and those with exaggerated wattles.
