English: A photo of a sick pigeon (Columba livia). "The domestic pigeon (Columba livia) 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." (Wikipedia)