Many domestic birds have escaped or been released over the years, and have given rise to the feral pigeon. These show a variety of plumages, although some look very like pure rock pigeons. The scarcity of the pure wild species is partly due to interbreeding with feral birds. Domestic pigeons can often be distinguished from feral pigeons because they usually have a metal or plastic band around one (sometimes both) legs which shows, by a number on it, that they are registered to an owner.
