Genetics
The Greywing is an autosomal mutation of the dil locus with the symbol dilgw, and so is a member of the multiple allelic series which also includes the Dilute (dild) and Clearwing (dilcw) mutations. The Greywing allele is recessive to the wild-type, dominant over the Dilute allele and co-dominant with the Clearwing allele.
The effect of the Greywing mutation is fully visible only in a bird which is homozygous for the Greywing allele with the genotype dilgw/dilgw or is heterozygous with the Dilute allele, with genotype dilgw/dild. The effect is to reduce the number of melanin granules in both the cortical and medullary cells of feather barbs over the whole body by around 50%.
When heterozygous with the wild-type allele with the genotype dil+/dilgw the phenotype is identical to the wild-type Light Green and the bird is known as a Greywing/dilute.
When the Clearwing and Greywing alleles are both present the genotype is dilcw/dilgw and the bird is known as a Full-bodied Greywing. Both alleles are partially expressed, giving the bird wings like a Greywing and a body coloured like a Clearwing. A fuller description is given under Appearance above.
Read more about this topic: Greywing Budgerigar Mutation