Fallow Bourke's parakeet (W-2)
sand coloured fallow
Description: Both pictures are made by the family Naujoks, friends from Germany, breeders of the fallow Bourke. Both pictures depicts the same bird. It was not easey to find out what the gender was because of the frontal band is hartly seen. The blue stripe above the eye is missing also. The eyes are red. Beack and nails are horn coloured. Head and throat are brown rose. We see this very clear in the picture below. The colour of the wings is warm brown. The wing coverts are dark brown with light brown margins. The shoulder and bend of the wing are cobalt blue. The back is yellow brown. The tail is brown. The under tail coverts are very light blue.
Name giving: The most exact typifying of this colour I found in literature was: sand coloured brown. The plumage and horn parts are diluted as a whole. The eyes are bright red. The brown plumage is much lighter then the plumage of the wild-type brown Bourke. Therefore the red and yellow pigments are more visible. The belly becomes bright red. The breast , neck and throat become brown rose. The loss of the eumelanin on the back gives the warm yellow brown colour. The distribution of psittacine pigments in the plumage is the same as in the wildtype.This pigments are coming forward. Beckmann found a reduction of about 75% in the barbs and about 50% in the barbules. The inheritance is recessive.
Beckmann studied cross sections of feather barbs of the Bourke and found a strong reduction of the amount of melanin grains in the fallow Bourke's parakeet. In respect of the fallow Bourke he found a quantitative change of melanin grains. Not a change of colour and format of the grains.
Picture of a wingcovert of the fallow Bourke, redrawn after Beckmann
Discussion: Beckmann is an expert in the genetics of the budgerigar. He did research on the budgerigar about three fallow mutations of the budgerigar. He described the fallow mutations of the budgerigar as a change of the black into brown-grey eumelanin. The three fallow budgerigars are inheriting recessive. The colour of the eyes is red. In respect of the fallow budgerigar there is a qualitative change of the melanin grains. The shade of the plumage is grey brown. The fallow melanin granules are much smaller and numourus. (W.Beckmann: "Handleiding voor de grasparkieten kweker" (1966, page 96). Although the historical name of the fallow colour variety of the Bourke is the same, the cause of this colour variety is different.
T. Martin gives in his book: " Colour mutations and genetics in parrots", 2002, a standard definition of the fallow. Criteria are: recessive inheritance, red eyes, change of all black and grey pigments in light brown eumelanin. The Bourke's parakeet does not fit in this definition. The wildtype Bourke has brown eumelanin. The fallow Bourke is sand coloured brown. He has red eyes. The inheritance is recessive. There is no change of black into grey or brown eumelanin. Beckmann found a strong reduction of the amount of melanin grains.
Extension of the definition: In the discussion about fallow mutations in different species the definition is extended.. Two groups of fallows are distinguised: the first group has light grey or grey brown melanin pigments. The second group has brown or light brown melanin. Mutavi is using the name dun fallow for the fallow Bourke. Dun fallow belongs to the first group with light grey or grey brown melanin pigment. Dun (English) means mause grey. This can not be a proper name for the Bourke. It is not useful to use the name dun fallow for the sand coloured Bourke because he does not fit in the standard definition and not in the extended definition as well.
For the time being I use the historical name sand coloured fallow. Maybe new research would be significant to produce evidence for the findings of Beckmann and find a better name for this colour variety of the Bourke.
Development: The colour variety is developed in the same decade as the yellow pastel Bourke. But it is an other eumelanin mutation. Mating the fallow and the yellow pastel Bourke gives only wildtypes, split for both factors.