High Quality Content by WIKIPEDIA articles! The English Grey budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It appeared briefly in the 1930s but was lost shortly after and until recently was believed to be no longer extant. However, the appearance of the Anthracite budgerigar mutation in 1998 with a seemingly identical appearance and identical genetic behaviour, insofar as can now be determined, suggests the mutation may have been regained.