4.5 The Dark Factor


The dark factor gene is an incomplete dominant gene that causes the darkening of the melanin (blue/black pigment) in birds. Since the gene is incomplete dominant, two dark genes (DF) have a greater effect on the bird than a single dark gene (SF). To understand the effect of the dark gene on a bird, imagine that you put on dark sun glasses and look at a normal green bird. The green appears darker and the bird is called dark green. With a double dark factor imagine that you are looking through two pairs of dark glasses. The bird will appear darker still and this colour is called Olive. Similarly if the bird is a visual blue, a single dark gene causes the blue colour to appear darker and the bird is called a cobalt. Two dark genes further affect the blue colour and the bird is called a mauve. The following table shows the effect of the dark genes on green and blue birds.

 

In our markets a grey-green is often wrongly called an olive. Please note that an olive bird is genetically very different from a grey-green bird (and much more valuable). You may visithttp://bestofbreeds.net/wbo/budgerigarcolourguide.htm to see the difference in colour.

Let us work out a sample pairing.
Dark Green Split Blue X Sky Blue

 
We get
25% Green Split Blue
25% Dark Green Split Blue
25% Sky Blue
25% Cobalt

Homework
Try the following pairing
Mauve X Green Split Blue

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