What's in a name? Nomenclature for colour aberrations in birds reviewed

Summary. A review is presented of the seven commonest types of colour aberrations in birds together with suggestions for a standardised universal nomenclature to identify and distinguish these aberrations. These aberrations are: Leucism (congenital absence of melanin-producing cells), Progressive Greying (progressive loss of melanin-producing cells), Albino (total absence of melanin due to lack of the key enzyme), Brown (incompletely coloured melanin), Ino (even less completely coloured melanin), Dilution (altered deposition of melanin) and Melanism (altered distribution of melanin). It is proposed that these terms should be based not only on the resulting plumage but also should distinguish the underlying processes resulting in the aberrant pigmentation. By reviewing previously used terms for colour aberrations, and cross-referencing these with my proposed terminology, errors in earlier names are pointed out, and resulting in a more comprehensive nomenclature for colour aberrations found in wild birds. ‘There has been some confusion in the past in the recording and description of variant plumages … and this paper represents an attempt to clarify some parts of it.’ (Harrison 1963a)