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.