Extension and intensivation of psittacine pigment in rubino and red opaline-pastel and red edged varieties
The picture shows a red opaline-pastel hen (left) and a rubino hen Bourke's parrot (right). This birds I bred in 2005. The red pigment in the plumage of both hens is equal in extension and intensity.
The red opaline-pastel are striving for the colour of the rubino. The white three-cornered spot on the wing is striking. This white triangle is called the most important characteristic of the opaline variety. This white spot is due to a broad under wing stripe.
In the rubino the brown eumelanin, that is typical of the wild type Bourke, is total lost in the whole plumage. In the combination of the opaline and the pastel variety the brown eumelanin is lost in the greatest part of the plumage, the belly and the breast, head, neck, upper and lower back. In the wings the melanin is lost, with exception of the wing border, in the tail feathers, with exception of the end of the middle tail feathers. In the border of the wings the rubino shows a yellow band. The opaline-pastel shows in this feather field light brown wing coverts with yellow margins. The end of tail feathers and primaries are light brown. The pastel factor is the cause of the bleaching of the brown feathers in this places. Blue accents are totally missing in the rubino and nearly almost in the opaline-pastel. The blue structure can not express himself because of the lack of eumelanin.
A rubino Bourke is a very beautiful variety. The red pigment dominates in the plumage. The primaries are white, the biggest part of head and tail also. The little white spots are showing that the down is white too.
Beckmann wrote in 1972 that the red pigment in the original wild-type Bourke's parrot is restricted to the belly, breast and head. The belly is showing the most red pigment. Breast and head show lesser red. The Rubino and the Red opaline-pastel makes clear that selection during several decades brought a big extension and a higher intensity of the red pigment in the plumage.
Opaline, ino and edged and recessive pied Bourke's varieties are loosing melanin. This mutation factors are not the cause of this advanced pigment formation. They form the condition for extension the psittacine pigments. The real cause in the fact that it is possible to enhance the pigment formation by selection. The first selection of psittacine pigments took place since 1954. A lot of mutation breeders in Holland were busy with the developing of the yellow pastel Bourke. They tried to breed a variety as yellow as possible. In 1968 the first Edged variety was born. This cock had also psittacine pigments in the whole plumage. This took place (long) before the opaline Bourke appeared. And we know from personal contacts that the first breeder of the rose Opaline tried for years to develop a Bourke "as red as possible". In the development of the rose opaline ssystematic selection was preceding by Goossens (Holland) who bred the first rose Opaline.
The extension of psittacine pigments in the whole plumage of the Bourke's parrot has a long history. Just fifty years ago the first yellow pastel Bourke was born in the aviary of Mr. J van de Brink in Barneveld (Holland). Important was the selective breeding. in the following years by many breeders. The mutation had the effect of decreasing the melanin formation. A nice rose belly, breast and head and a yellow-brown upper- and lower back and a brown tail was the result. The hens were most yellow on the back.
It lasted till 1986 that a real bright yellow and red new variety came into being: the edged Bourke. Because of the total loss of melanin pigment in part of the plumage, for instance the back, rump and tail showed how far the psittacine pigments were extended. In all feather fields the psittacine pigments were present. Later on the opaline variety and the recessive pied also lost the melanin in some feather fields. The opalin came in 1972. This was a loss of the fore ground melanin in the hind neck, the upper back and a part of the wings. The camouflage structure in this places dissappeared. In 1990 The lutino arrived. Here a total loss of all melanin pigment showed all the yellow and red pigment that was present in the plumage.
There is a meaning that the mutation that resulted in the opaline variety is responsible for the extension of the psittacine pigments in the Bourke. This is an important question
What is the contribution of the melanin mutation that causes the opaline variety? In short: When the melanin is lost in the cortex there will be place for the psittacine pigments. When the melanin is lost in the medulla the red colour is brighter, more red than brown-red. When the melanin is lost in both, the blue structure can not be a hindrance for the expression of the red pigment., because there is no absorbing ground. Interesting is the research of Auber (1941) of the opaline characteristics.
Auber (1941) was researching the varieties of the Budgerigar. His point of view was strictly based upon morphology of the feathers. He studied the opaline Budgerigar also. He found that there are two changes caused by the mutation factor. First is the change of the cortex of the feather barbs. (see picture 1). The cortex becomes smaller. Second is the altered distribution of the melanin granules. The melanin disappears in the cortex. The amount of melanin in the medulla is increasing. The effect on the plumage is that the characteristic black striping of the feathers of the Budgerigar on the head, the hind neck and the saddle (between the shoulders) is gone. The original black colour of the stipes is replaced by the colour of the body. The empty space can can be filled up by yellow pigment. The Bourke's parrot has a camouflage structure also. When the foreground melanin is missing in the cortex, this empty space can be filled up by red or yellow pigment.
Auber found that the eumelanin pigment in the altered situation is situated around the vacuoles in the medulla of the feather barb. His conclusion was, in the opaline variety we see an altered distribution of the melanin on the micro level and and a change of the form of the cortex
The hypothesis that the distribution factor of the opaline variety should cause the increase of the red pigment. This cannot be true. It is a melanin distribution factor, not a psittacine factor. There is no scientific evidence for the hypothesis. The loss of the eumelanin pigment in the cortex forms the possibility for the extension of psittacine pigment. This can be red pigment, but yellow pigment also.
The process of formation the psittacine pigments is totally different than the formation of melanin. Also the distribution is a different process.In nearly all mutations that cause a loss of melanin in some feather fields, like recessive pied, edged, opaline, lutino and rubino Bourke's the red and yellow pigments can increase by selection. There are also other distribution factors on the macro level. The recessive pied variety is caused by a shortage of melanin production cells. Some featherfields, feathers or part of feathers don't have melanin.
By selective breeding the amount of melanin in the whole plumage is decreased also. The psittacine pigments can be increased by selection. Every breeder who followed the development of the opaline Turquoise Parrot, the opaline Bourke's Parrot from 1968 resp.1972 and the edged Bourke in the last thirty years can confirm that the melanin slowly decreased in the plumage by breeding this varieties. The effect of this mutation factors formed a condition for selective breeding of the psittacine pigments. I understand that breeders, who are since the last years were confronted by a well developed opaline variety can think that the whole extension and intensivation of the psittacine pigments is caused by this mutationfactor. But I know by experience that this isn't true. Auber showed that this distribution plays a role on the micro level. Extension of this concept to the macro level is inadequate. It negect the role of selection of the psittacine pigments.