List of non-native birds in Great Britain
Since the Victorian era many bird species have been introduced to Britain, whether for sport, ornament or general experimenting, and some have established themselves whilst others have not. Others have escaped from captivity and established themselves, though many species either die out after a few years or die off in harsh weather. This page lists the bird species that have established colonies in the British Isles. Some non-native birds have established themselves and become naturalised after naturally migrating to the country and forming colonies, such as the collared dove. The list  below comprises all those bird species which have occurred in a wild state in Great Britain. Escaped birds of certain species, e.g. ruddy shelduck, can cause confusion amongst birdwatchers as they occasionally occur in Britain as wild birds. The following species have established colonies in the UK at some point in time. They may have since died out, or new colonies established elsewhere. In addition to the species listed below, almost any bird kept in captivity (especially wildfowl) may escape and their origins may not always be obvious. Excluding the likelihood of captive origin is a major hurdle to be  faced by the British Birds Rarities Committee when assessing reports of rare and vagrant species to Britain.