Budgerigars, or Budgies, are one of the most popular pet birds across the world and are also hugely popular as breeding birds. Some people are happy to pair up two birds and see what comes out of the egg but for those aiming for certain colours or types then understanding colour genetics is a must. Here is a basic outline on the subject to help you understand what will come out of that little egg.
The wild colour of a budgie is called light green. The feathers of most of the parrot species, including the budgie, have two basic pigments in them, a black one called eumelanin and a basic yellow one called psittcofulvin (or psittacin). Some parrot species have a third pigment called advanced psittacin that enables colours and tones to change to colours such as oranges, red, pinks and peaches.
When these coloured feathers are exposed to white light such as sunlight, only the blue part of their spectrum shows up so the green colouration is what we see, light green on budgies and a range of other greens on other parrots.
There are at least thirty-two known primary mutations that have been established in budgies these can combine into hundreds of secondary mutations and colour variations, some of which are one-offs and others are reliably bred. While a book can, and probably has, been written on these mutations, here we are going to look at the basic and more common ones only.
Each of the thirty-two primary mutations fall into one of four basic groups. These are:
The other basic definition of the mutations is by their dominance relationships. This is the relationship between alleles of one gene where one is dominant to another. The first is called the dominant while the second is called recessive. There are two types of chromosomes that are composed of these alleles; sex chromosomes and autosomes. Therefore, the dominance relationship (which will make more sense when applied to colours) are as follows:
The dark mutation in budgies comes in two green series colours, Dark Green and Olive and three blue series colours, Cobalt, Mauve and Violet. These birds are identical to wild-type light green or normal blue birds except for their body colour and tail feathers. The body colour is darker in the Dark Greens and Cobalts and even darker again in Olives and Mauves with all birds having a darker tail feathers while still retaining the normal violet cheek patches.
A dark green bird is described as a shade of forest green while a Cobalt is a deep blue similar to azure. Olive green is a rich olive shade that can be distinguished from the similar Grey-green by the cheek patches while mauve is a purplish grey.
In the genetics, the dark mutation has an incomplete dominant relationship with the wild-type allele so for example, a dark green bird has one dark allele and one wild-type allele while the olive has two dark alleles. The dark factor is always visibly expressed so no bird can be split for dark.
In the blue mutation, the feathers that are light green in the wild type bird change to sky blue while the mark and other areas that are yellow change to white. Blue mutations are recessive to the wild type allele so that a bird with a single blue allele appears the same as a wild type bird. This bird would be described as a light green split blue (Light Green/Blue). A bird that has two blue alleles doesn’t have the yellow pigment in its feathers so the blue colour comes out. When combined with the dark mutation, colours such as cobalts, mauves and violets.
This is a variety of the blue mutation whereby the normally white face is yellow and there are some pale yellow wing markings but all other colours are the same as a blue bird. Yellowface I is an autosomal recessive mutation in relation to the wild-type.
The Yellowface II is a shade mid-way between blue and green, often called sea-green or turquoise. This changes to a bottle green in a Yellowface II Cobalt and mauve and olive on a Yellowface II mauve. When combined with blue, opaline or clearwing, it produces a rainbow bird.
The dominant grey is a mutation that is the basis for grey-green and grey variations. It turns the light green into grey-green and sky blue into light grey. Grey green sees the body colour become a dull mustard green with a duller yellow mask while the light grey is a battleship grey in colour. Because grey is a dominant mutation, a bird with a single allele is a grey bird, even over the wild-type colour. Double-factor birds appear the same as single factor birds also due to this.
The violet factor affects the visual colour of any bird carrying it and there are current 18 different variation using it. Single factor violet light green birds have dark green feathers but without the ribbing on the body feathers giving them a satin-like look. Blue series birds with single factor violet look like pale cobalts.
The Clearwing mutation combines in a range of different varieties to produce different birds. When combined with green birds it is known as the Yellowwing, with blue birds as a Whitewing while combined with the greywing variety, it is known as the full-bodied greywing. Combinations with the yellowface II and opaline mutations result in the Rainbow mutation.
This is just a selection of the mutations of the budgie that can be bred and all have further differing mutations within each definition.
*Please note the genetics definitions are from Wikipedia and are kept nearly the same to avoid mid-quoting a rather complicated subject*