Analysis of the violet colour variety

Violet Bourke's

1. Analyse of the mutation factor (part of the genotype)

2. Analyse of the colouring of the plumage by pigments and feather structure (part of the phenotype).

Analysis of both aspects is needed for a succesful development of varieties. The study of research- results, combined with the experiences of birdfanciers, who are breeding the variety, is needed. In this way science and praxis are working together.

ad 1: Mutation factor: The violet mutation factor is co-dominant. (code V). This factor inherits independent. This means that the violet factor lays at another pair of chromosomes then de dark factor. The single factor violet gene (code V) lays at one chromosome, the double factor violet (code VV) lays at both chromosomes.

ad 2. Expression of the violet factor: The violet mutation took place some years ago but became unnoticed. What was the reason? The double factor violet (VV) can be expressed immidiately. The single factor violet (V) can express himselve only in combination with a single darkfactor (code VD). The two factors, the darkfactor and violet factor are laying at different chromosomes. Both factors are controling yhe feather structure. They influence the bluestructure and barb.

Conditions: The colour expression of the violet-mutation depends on three conditions in the wild-type or the varieties.

1. Feathertype: The expresssion of the violet factor depends on the feather type. There are two different feather types. Feathers of the common type and feathers of the structural type. Most parrot species have both , some featherfields have fathers of the common type, other featherfields have feathers of the structural type. The violet mutation is a mutation, that changes the shape of the barb and the form of the blue structure. Feathers of the common type don't have a blue structure. Expression of the violet factor in this type is impossible. The violet colour is restricted to feather fields of the structural type. Knowledge of the feather types in all feather fields is needed. to predict the extension of the violet colour.

2. No presence of yellow pigment in de cortex: In green parrot species the yellow pigment in the cortex has to disappear first by mutation before the violet factor can express himself. An example is the wildtype budgeriar. In blue featherfields there is no hindrance to expression. An example is the wild-type Bourke's parrot. In the blue featherfields there is no yellow pigment in the cortex. The wildtype Bourke's is brown. He don't has a green plumage. He has not a single green feather. In the Bourke's is the second condition fulfilled already. The violet factor can express himself directly.

Comment: In the green budgeriar total loss of yellow pigment is needed first. This mutation factor is called "blue" factor. More understandable would be:"total loss of psittacine pigment" factor. The colouring of the green budgeriar means that t blue structure and the yellow pigment working together in colouring. When the yellow pigment is gone by mutation the bluestructure is prescribing the blue colour. Species without feathers of the structural type, like the yellow cockatiel, the effect is different. When the yellow pigment is gone. The plumage becomes white and grey. A galah shall be white-fronted, but not blue. Conclusion: The mutation name don't has validity, because of the different results in different species.

3. Darkfactor: A single factor violet (code V) don't come to expression directly. When the single facotor is combined with a darkfactor (D) then the violet factor can express himself. Why? The darkfactor alters the shape of bluestructure. The violetfactor alters the blue-structure and the shape of the feather barb The combination of this two mutationfactors (VD) brings about the violet feather

Conclusion: When breeding the violet variety three conditions have to be fullfilled: 1. Feathers of the struktural type, This can be the whole plumage or a variable amount of featherfields. 2. The absence of pigment in the cortex. The cortex has to be transparant. 3. An altered bluestructure. and shap of the barb. The violet colour is the result of a combination of a darkfactor and single violetfactor(DV) or a double violetfactor (VV)

4. Variability of the effect of the violetfactor on the plumage: The effect of the violet-factor depends on the three conditions. The extension of violet colour is variable. The violet variety of the green budgeriar is violet with a white mask and head. The violet blue masked lovebird is violet with a black head and white chest, the violet Bourke has some violet featherfields, a violet cockatiel is not possible. .

The Bourke's parakeet. Green parrots have to meet three conditions for expression of the violetfactor. The Bourke's parrot has to meet two conditions. The extension of structural featherfields in the wildtype is restricted. The structural blue mutation in the Bourke's will be a very interesting factor in the developing of a beautiful violet variety.

The violet factor brings a lot of changes in the feather structure. The drawing is made by L.Auber (1941) . He studied the wild-type and the "Australian violet. The wild-type has violet spots in the mask. The variety is a combination of three mutation factors. The variety has a bright bluish violet colour.

Cross-section of a violet feather

One of the things that attract the attention immediately is the bright shining colour. The surface of a violet feather is catching and reflecting more light a blue feather. The cross section of the violet feather barb shows a broader diameter then a normal feather barb. There are more vacuoles and they are arranged rgularly. The cortex is broader than normal and is transparant. The blue structure is a little bit smaller then in dark feathers. The eumelanin particles around this vacuoles and the blue structure are directed regularly. This granules are neatly packet around each vacuole and forms together a perfect absorbing medium. The violet colour is very attractive to observers.

The violet variety of the Bourke's parrot

The violet factor in the Bourke's comes to expression in the blue featherfields.only. The featherfields are: forehead, shoulder, outer parts of the wings, under wing coverts, under tail coverts, flanks and outer tail feathers. These are feathers of the structural type. The other parts of the plumage of the wild-type have feathers of the common tupe according to the result of research of Beckmann in 1973.

Conclusion: 1. The blue featherfields are feathers of the structural type. 2. The blue feathers don't have yellow pigment. This condition is fulfilled already. 3. Combined with a dark factor the blue feathers become violet. 4. Combined with the structural-blue factor, the extension of th violet colour to the upper- and lowerback, part of the wings, the tail and the forehead is an interesting possibility.

A picture of the Cobalt variety

of the Bourke's parrot

An extension of the structural featherfields in the back is already realised. The combination of the violet factor with the structural blue factor shall give a variety with violet the colour in a big part of the plumage. The picture shows a recent specimen of the structural-blue variety of the Bourke with a big extension of the structural feathertype.

Some pictures of the violet-wildtype Bourke's

Head study

Backside of the violet-wildtype Bourke's cock born in 2008

Violet-rump and outerpart of the wings

Combination of the pastel-dark-and violet factor

Violet-pastel rump and outer wing feathers

Violet-pastel wing

Copyright 2009 by Bob Fregeres

index menu

E-mail: fregeres@telfort.nl