so a bird possessing a single English Fallow allele (the heterozygote, fe+/fe) is identical in appearance to the wild-type light green. That is, the presence of a single wild-type allele is sufficient to permit the full production and normal distribution of the black melanin pigment. Among the budgerigar fancy such a bird is said to be a Light Green split English fallow, usually written Light Green/English fallow. In a bird which has two English Fallow alleles (the homozygote, fe/fe), the lack of the wild-type allele means that normal black melanin pigment cannot be produced. Instead a pigment giving a brown appearance is substituted, resulting in brown markings where black would appear in the Normal. Notes References External links World Budgerigar Organisation (WBO) WBO Colour Guide Fallow Budgerigars, Ken Gray Fallow Budgerigars hug book Classifying and defining Fallow colour morphs in Parrots, Terry Martin The Fallows, Ghalib Al-Nasser The Fallows, Cyril Rogers Budgerigar colour mutations