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Genetics of Blue Feathers
by an Unknown Author edited by Alan Stanford, Ph.D.
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Blue, as in Andalusian Blue, is caused by a “modifying gene”, an autosomal, incompletely dominant gene (Bl) that, when bred to a “pure” black bird, produces the desired “Andalusian Blue” only in the heterozygous form.
In the Andalusian Blue, the ideal feathering is be an even shade of ashy, blue-gray throughout the bird, with each feather laced in black. The edges of the feathers are black; the birds look like Black Silkies until you see their undercoat. The female birds look more evenly colored, while the males are very black in the hackle, saddle, and wingbows, due to their sexually dimorphic plumage.
Inga Ladd pointed out to me, “the standard refers frequently to ‘blue clearly and sharply laced with bluish black.’ The darker hackle is required in males and females. Of course, with Silkies, nothing is ‘sharp’ because of the feather structure. You will see a slightly darker hackle on males; with females it is a darn subtle thing.”
There are many genes that darken or lighten the blue color; this includes factors causing smut or mossiness in the otherwise pure blue areas of the feathers. It might be said that “Blue” is actually “Black Laced Blue”.
The Andalusian blue gene, when homozygous , creates “Splash” or “Blue Splash” feathers. These birds are muddy or bluish white with occasional, randomly “splashed”, black feathers. Splashed plumage can be very attractive, especially in Silkies. A variant to the Andalusian Blue has feathers edged in Dark Blue instead of Black.
This, unfortunately, simplifies the genetic process. Many interacting factors determine the color of feathers; breeding “perfect” show-type Blue birds is a constant struggle for even the experts.
Self blue, also know as Lavender or “true breeding blue”, is an genetically disticnt from Andalusian blue; birds can have both Andalusian and Self blue genes. Self blue is controlled by an autosomal recessive gene (lav). In other words, it is only expressed in the homozygous form, and therefore is not a modifier and can only be “blue or split to blue”. Lavender birds also tend to be more of a uniform blue, male and female, without the smut or mossiness often found in Andalusian Blue birds. There is, however, some linkage or other attribute that shows up in lavender birds which often causes the shriveling or narrowing of the long feathers of the wings and tails. This deformation renders many birds not suitable for the showroom.
When referring to APA or ABA Standard bred birds, Blue refers to “Andalusian” Blue and Self Blue refers to “Lavender” or “True Breeding Blue”.
I forgot to mention that Lavender birds are not laced.
Dark Blue Laced Blue is a British thing. Carefoot describes it, but I don’t think I have ever seen it. It is possible that the Blue Laced Blue of the UK is the combination of Lavender and Andalusian Blue, since they can be inherited separately. Andalusian Blue is very common in the USA, even though it is only phenotypic when heterozygous. Blue Andalusian chickens were part of the original (1874) APA Standard. They purportedly came from crossing native black Spanish fowl with their white “sports“. As you know, white sports (not albinos) occasionally occur in virtually all black species.
The Lavender gene modifies the pigment granules of the feathers (Hollander). The Lavender gene causes Black to appear Blue, Red to appear Buff and Red-Orange to appear Straw.
I don’t know when the Lavender gene was discovered. Buff coloration was standardized in the nineteenth century. Self Blue was described as a standard color in the first ABA, Bantam Standard in 1965. Self Blue Old English Games were admitted to the APA American Standard of Perfection in 1965, also. Self Blue (or Lavender) is much more uncommon, though it occurs in several Standard breeds. The British Poultry Standards admitted Lavender “Araucanas” at a later date.
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