Gouldian Finch Genetics. An introduction to: Head, Breast & Body color mutations and their patterns of inheritance. © Gouldians Galore 2009. Useful Genetics Terms. Trait : A trait is a physical characteristic that can be inherited (e.g., head color).
An introduction to:Head, Breast & Body color mutations and their patterns of inheritance.
© Gouldians Galore 2009
In birds, the sex chromosomes are labeled “Z” and “W,” where males are genetically “Z Z” and females are genetically “Z W.”
In Gouldian Genetics, “sex-linked” always refers to genes located on the “Z” sex chromosome(s).
RH Male BH Male OH Male
RH Hen (w/pins) BH Hen OH Hen*
*Photo courtesy Lainey
Alexander of Grasslands
Again, a sex-linked gene is one that is located on the Z sex chromosome(s).
Red and Black head color are controlled by the same gene and can be understood as two “alleles” (varieties) of this gene.
Because this gene is sex linked, males can either be “single factor” or “double factor” for each, whereas females can only ever be “SF” for red or “SF” for black. If you remember that females are ZW and males are ZZ, this makes sense.
Where R = Red Allele
and r = Black Allele
The following photos illustrate BH (OTB) birds. Photos generously supplied by Lainey Alexander (BH OTB Males) and Misty LaRue (BH OTB Hens).
BH OTB Males
BH OTB Hen
R/R o = DF Red Head/Orange Head Cock
R/r o = SF Red Head/Orange Head Cock (Essentially RH/BH/OH)
r/r o = Black Head/Orange Head Cock
R/R o o = Orange Head Cock
R/r o o = Orange Head/Black Head Cock
r/r o o = BH (OTB) Cock
R o = Red Head/Orange Head Hen
r o = BH/Orange Head Hen
R o o = Orange Head Hen
r o o = BH (OTB) Hen
Because hens can only be SF red or SF black, you can see that unlike cocks, hens can never be “triply split” for head color.
I.e., you will never see a “RH/BH/OH” Hen.
Some body colors affect the head colors in the way they visually appear.
For instance, the presence of the yellow body gene affects the color black. Black Head birds will appear charcoal grey to off-white in color if they possess the yellow body gene.
The blue body gene affects the colors red and orange, transforming these head colors to a salmon to beige color.
c/o Misty LaRue
These photos illustrate the variety of LB males.
Before continuing; note that there exists different nomenclature for the mutations between continents. To avoid confusion, I will use the nomenclature I find to be consistent with U.S. Aviculture.
The “yellow gene” is responsible for the following mutations:
Yellow is a sex-linked mutation located on the Z chromosome, so males are capable of inheriting up to two copies, while females can only ever inherit one.
Yellow is understood to be “incompletely dominant” to the normal green body color.
Incomplete dominance results when two genes “combine” to create a visual “intermediate.” Consider the following:
Pea plants are capable of producing flowers that are Red (RR) or White (ww). However – if a Red pea plant is crossed with a White pea plant, the colors “combine” in the heterozygote (Rw) – creating a flower that is neither Red, nor White, but Pink.
Adding the Yellow mutation to a Normal Gouldian male produces a similar result.
Yellow is sex-linked, so males have the ability to inherit either one or two copies.
When one copy is inherited, and the bird is Purple Breast, we see the incomplete dominance take effect.
The single yellow gene “competes” with the remaining genes responsible for normal green body, and the bird becomes an intermediate mixture of yellow and green, appearing “Diluted” when compared to a normal Gouldian.
Two BH Dilute Juveniles – the juvenile in the foreground is just
heading into his first molt.
What happens if a male inherits a single copy of the Yellow gene, but he is not PB?
Due to an underlying correlation between Lilac and White breast color and the yellow body color gene, visually Lilac or WB males that inherit even a single copy of the yellow gene will be visually yellow in body color, not Dilute.
For this reason, they are often called “Single Factor Yellow” males, as they inherited a “Single” copy of the gene, and they are visually “Yellow” in body color.
A question often asked revolves around distinguishing SF Yellow males from “DF Yellow” males. A few tricks involve noting the turquoise band behind the mask of the bird and how bright it is. On a SF Yellow – such as this bird – it will be brighter blue. Also, the normally black bib under the beak will appear a more grey color, whereas on a DF Yellow male the bib will be almost completely white and the Turquoise band more of an opalescent color.
Females can never be dilute. This is because they are only capable of inheriting a single yellow gene (Z^y W), and thus the single copy completely masks the expression of the genes responsible for green body color, and they appear yellow as a result.
For this reason, as well, it is redundant to say a female is “SF Yellow,” and also impossible for a female to ever be “DF Yellow.”
RH PB Yellow Hen
A male that inherits two copies of the yellow gene, regardless of his breast color, will be visually yellow.
This is because the presence of two yellow genes completely overrides the genes responsible for green body color – resulting in a bright yellow bird.
RH PB DF Yellow Male
The “Blue Gene” is responsible for the following mutations:
Blue is an autosomal recessive mutation which means that it is not inherited on the sex chromosomes. This also means that both males and females can be either SF or DF for the gene, but will only express it if they are DF.
A RH, PB Blue Male
A BH, PB Blue Hen
Because Blue Body is recessive, a bird can inherit a single copy and be “Split” for Blue.
There is no reliable visual way to distinguish split to blues from regular normal birds.
So, the genetic possibilities are as follows:
Normal + b = Normal/Blue Bird
Normal + bb = Blue Bodied Bird
Pastel Blue is the result of combining the Yellow and Blue genes together.
Pastel Blues are Blue birds that are also SF Yellow. They will always have a Purple Breast.
You can think of it as being similar to Dilute birds.
The presence of the single yellow gene “subdues” the brilliance of a normal Blue bodied bird, transforming it into to that of a light, powder blue gray color instead.
The genetics of a Pastel Blue Male are as follows:
SF Yellow + Blue Body + Purple Breast
Again, because females can only be SF for Yellow (causing complete expression), only males can ever be Pastel Blue.
A RH PB Pastel Blue Male
There are two types of Silver Bodied males:
Silver (SF Yellow) + White or Lilac Breast
Silver (DF Yellow) + Any Breast Color
When a male that would ordinarily be Pastel Blue does not have a Purple Breast, but is instead Lilac or White Breast, he becomes visually Silver in body color instead. This is similar to why a SF Yellow WB bird appears Yellow instead of Dilute.
Photo graciously supplied by Misty LaRue.
A Blue bodied male that is also DF Yellow will always appear visually Silver in body color regardless of the color of his breast.
Juvenile RH PB Silver (DF Yellow) Male
Because females can only be SF for Yellow and express it, a Blue Bodied hen that also possesses the Yellow gene will appear visually Silver in body color regardless of her breast color.
RH PB Silver Hen
So, the genetic possibilities for Silver Body are as follows:
SF Yellow + White or Lilac Breast +Blue Body Male
DF Yellow + Any Breast Color + Blue Body Male
Yellow + Blue Body Hen
Creating an “all white” Gouldian can be accomplished by producing a Silver bird that is also Black Head and White Breast.
This is because the Yellow gene transforms the Black Head color into a Charcoal Grey to White Color. (SF Yellow males will have a grey colored head, whereas DF Yellow Males and Yellow hens will have a nearly white colored head instead)
BH WB Silver Hen