Breast Color Genetics
Gouldians come in three recognized breast colors:
These traits can be understood as different "alleles" of one gene. Meaning - breast color is defined by one gene, and there are three different alleles (read: varieties) available - one for Purple, one for Lilac and one for White. This means that no bird can ever be triply split for each allele. i.e., no purple/white/lilac bird will ever exist!
Purple Breast (PB)
Purple breast is an autosomal dominant trait to both lilac and white. Cocks and hens can both be SF or DF for Purple breast. However, a bird that possesses at least one copy of the purple allele will always be visually purple breasted. The only way to know if your bird is split for lilac or white is by test breeding it to a lilac or white bird - if you get lilac or white babies, you know your bird is split! Purple breasted birds occur in all body color mutations.
Lilac Breast (LB)
Lilac breast is recessive to Purple but dominant to White. A bird that is visually Lilac Breast will either be DF Lilac or Lilac/White. The Lilac breast color is interesting particularly in males due to the variation of Lilac color seen. This appears to be directly related to the amount of melanin reduction in males. That is to say, a normal bodied male that is LB will have the darkest Lilac color. A SF Yellow male that is RH will be slightly lighter, DF Yellow RH males even lighter, and BH DF Yellow males being the lightest lilac.
White Breast (WB)
White breast is recessive to both Purple and Lilac. The only way a bird will be visually white breasted is if it is DF for the White allele (no visually WB bird will be "split" for any of the other two breast colors).