Escape
An individual found in the wild but which originated in captivity, either having escaped or having been freed deliberately. The most frequent escapes are popular types of cagebird, like Budgerigars Melopsittacus undulatus and Canaries Serinus canaria, together with wildfowl from outdoor collections. The feral Ruddy Ducks Oxyura jamaicensis and Ring-necked Parakeets Psittacula krameri found in Britain originated as escapes, and the former has been admitted to the British List. In the case of species which might occur naturally in a particular area but which are also kept in captivity, it is often difficult to decide whether a sighting refers to a genuinely wild bird or an escape, this problem being especially acute with geese (family Anatidae).From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver