Javan Mynas with unusual plumage colour

posted in: Morphology-Develop. | 0

YC Wee: “A pair of Javan Mynas (Acridotheres javanicus) appeared in my garden some months ago, both with the same unusual plumage colour. The mantle, breast and belly have a distinct bluish tinge compared to the dark grey seen in most Javan Mynas. This is not photographic artefact as the colouration of the image below is exactly what was seen in the garden. Subsequent to this sighting, I began to see a variation of this, with the bluish parts becoming less prominent (below). Intrigued, I sent images to aviculturist Lee Chiu San and below is what he has to say.”

Lee Chiu San: “No I have not seen this in mynas, but there are defective genes that cause colour lightening, and they have been studied in sheepdogs, parakeets and cats.

“There are various manifestations of the gene, but in layman’s terms, you could relate it to an incomplete form of albinism.

“In parrots and parakeets it gets more interesting. You know that there are captive bred blue varieties of many parrot species that are naturally green, among them budgerigars, various Psittacula, Amazon parrots, lovebirds and Quaker parakeets.

“Any art student will tell you that green is a combination of yellow and blue pigments. Therefore, if birds are missing the yellow gene, they appear blue. If they are missing the blue gene, they appear yellow. This variety (not albino) is known as lutino in aviculture. There are also many captive-bred lutino varieties.

“if they are missing both genes, then they are albino.

“Siamese cats and white tigers are not full albinos, but only partially so. They are missing some colour genes, so parts of the body that would normally be pigmented are light. And their eyes are blue. Take a good look at the white tigers in the zoo and notice that their colour patterns are lighter in the middle of the body and more pronounced on the legs, face and tail, as in a Siamese cat. And the white tigers also have blue eyes.

“Now, coming to animals that are naturally black, such as the black and white working sheepdogs (not the ‘Lassie’ brown and white dogs more well-known on television) there is a colour known as blue merle which is caused by a defective gene. This causes areas that would normally be black to be blue-grey in colour, no doubt with a scattering of black.

“I would describe the myna in the photo as displaying something like a blue merle base colour.

“If you say that there are two birds with this pattern in your garden, they could be siblings, both with the same genetic make-up.”

Lee Chiu San & YC Wee
Singapore
13th May 2018

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