Dark Factors
By Brett Doran
One of the reasons budgerigars are so popular both as pets and as exhibition birds is the range of varieties and colours that are available. In this article I will concentrate on colour rather than variety, as colour production is consistent irrespective of variety.
In both green and blue series there are three basic colours as follows:
Light Green
Skyblue
Dark Green
Cobalt
Olive Green
Mauve
We also have two modifier genes, which aren't colours in themselves, but as the name implies they modify or change the base colour. These modifiers are Grey and Violet. We will deal with these modifying genes in a future article, while in this article we will confine ourselves to the basic colours. As you can see in both green and blue series birds there are three shades of colour. The presence or absence of what we call "Dark Factor genes" produces these shades. The arrangement of dark factor genes is as follows and is expressed by the use of "d" or "D".
No dark factor dd Light Green Skyblue One dark factor dD Dark Green Cobalt Two dark factors DD Olive Green Mauve As can be seen above, genes are always grouped in pairs, with one gene passed on by each parent. Lets look at some pairings using dark factors.
Before we start I will be using what are referred to as "Punnet Squares" to demonstrate each pairing. In the examples I will be using it doesn't matter which gene pair, horizontal or vertical represents the cock or hen. Percentage results are based on results over many nests and may vary for individual nests except of course where the expectation is 100%.
Lets start with a simple pairing such as Light Green (Skyblue) x Light Green (Skyblue). As can be seen from the above list Light Greens (Skyblues) possess no dark factor ie "dd".
d d d d d dd dd d dd dd d dd dd d dd dd 100% "dd" no dark factor ( Light Green or Skyblue).
As can be seen the resulting progeny are all no dark factor birds, therefore all Light Green (Skyblue).
Now lets pair Light Green (Skyblue) x Dark Green (Cobalt).
d d d d d dd dd d dd dd D dD dD D dD dD 50% " dd " no dark factor ( Light Green or Skyblue).
50% " dD " one dark factor ( Dark Green or Cobalt).
As can be seen 50% carry no dark factor (Light Green or Skyblue) and 50% carry one dark factor ( Dark Green or Cobalt).
Our next pairing is Dark Green (Cobalt) x Dark Green (Cobalt).
d D d D d dd dD d dd dD D dD DD D dD DD 25% "dd " no dark factor ( Light Green or Skyblue).
50% " dD " one dark factor ( Dark Green or Cobalt).
25% " DD " two dark factors ( Olive Green or Mauve).
This pairing produces an unexpected result to the inexperienced breeder who would assume that pairing two Dark Greens (Cobalts) would result in all the progeny being Dark Green (Cobalt). As can be seen from the above result this pairing in fact produces birds in all three shades of green (blue).
For our final pairing involving two green series birds we will pair Light Green (Skyblue) x Olive Green (Mauve).
d d d d D dD dD D dD dD D dD dD D dD dD 100% " dD " one dark factor ( Dark Green or Cobalt).
Hopefully you are getting the hang of this genetics stuff by now. Was this the result you expected? Once you understand the basic methodology of the punnet squares it all falls into place quite readily.
Lets pair a Light Green x Cobalt to prove that the dark factor theory holds true even when pairing green to blue.
Now that you possess this basic understanding of Dark Factor Genetics you will be able to pair whatever varieties you like and be able to work out the basic colour expectations for that pairing whether it be Normals, Dominant Pieds, Clearwings, Opalines or Cinnamons etc. As mentioned earlier we will look at the modifier genes Grey and Violet and their effect on the basic colours in a future article. Until then may all your eggs be full and your chicks Champions.