This article will discuss the color indigo. As mentioned earlier, indigo is not one of the three basic colors found on the sex chromosome, but rather a gene modifier or mutation located on a different chromosome. Indigo originated in the Middle East, but was not recognized as something genetically different until the 1930's. Hollander and Levi worked out the genetics of indigo at that time. Depending on the base color, i.e. ash red, blue or brown, it will vary in expression. Indigo is dominant in nature and not sex linked.
In earlier articles I discussed genetics and sex-linkage, and how the cock bird carries two sex chromosomes and the hen carries one. This is the only time this occurs, with the sex chromosome. With all other chromosomes, the hen can have two. This is where the terms heterozygous and homozygous come into play. The gene indigo can be present in a cock or hen, whether once or twice. One indigo gene would indicate heterozygous, two would mean homozygous.
The most common usage of indigo is in combination with the blue series as this produces the most attractive colors. Indigo in combination with ash red produces offspring that appear to be just ash red, except that they may show a more purple tint to the rump or head. Some may not, and only by breeding them and observing their offspring will you know their true genetic makeup ! Indigo on brown is not very appealing either, but you could probably see it's influence enough to recognize it.
#1 
#2So, let's start with indigo in the heterozygous state on the blue series. Photo #1 shows a heterozygous indigo hen in the check pattern. This is probably the most common seen of the indigo king. The checks are a bronzy indigo color over a dark blue body color. The birds can vary in appearance depending on the pattern, i.e. check or t-pattern check. An indigo bar bird would look similar to a blue bar, but the body would be a little darker and the body would be this bronzy indigo color instead of black. Now let's look at homozygous indigo. Photo #2 shows a young king that carries two genes for indigo. I do not know the sex of this bird yet, but it can be a cock or hen. With homozygous indigo you get a bird that mimics ash red. It appears ash red over most of the body except that there may be some indigo or plum color on the rump and the head is usually dark colored, sometimes looking like a mask. Compare Photos 1 and 2. They look very different, but both are indigos ! This particular bird was raised from 2 andalusians, but you could get the same color from an andalusian and an indigo or from 2 indigos. the main ingredient here is 2 doses of indigo, one from each parent.
#3 
#4Next we will look at andalusian. This is considered the most attractive of the indigos. An andalusian is actually indigo with the addition of the gene for spread. When you add the spread gene to blue, you get black. When you add the spread to indigo you get andalusian ! However, andalusian will only show up on the blue series pigeon that carries spread, in other words, a black mated to an indigo. A homozygous ash red spread or spread brown mated to indigo will not produce andalusian ! So, you can get andalusian by mating black to indigo, black to andalusian and andalusian to andalusian. Photo #3 shows the basic andalusian. Most good colored andalusians will have a darker color of lacing on each feather, adding to the beauty of this color. Photo #4 shows another andalusian, this one lighter in color than #3.
Photo #5 shows what can happen when you get a double dose of indigo and spread ! This young bird is a homozygous andalusian. Remember the homozygous indigo mentioned earlier ? It looks like an ash red except it has the dark head. Homozygous andalusian looks more like an ash red spread with the darker head and some darker color in the wing tips and rump. Some will be much lighter than this one and not show so much of the ash color on the body. After moulting, this bird will probably become lighter on the body and be very attractive.
#5 
#6And finally, in Photo #6 we have an indigo grizzle. The color does not show up too well in this photo, but the darker colors on this bird range from the bronzy indigo to the andalusian color. So, as you can see, indigo can be a fun color to breed as it can produce a large array of color combinations. There are also some very good quality show kings being raised in these colors, so competition can be stiff and winning a class in indigo can be very rewarding ! Of note is the color class for indigo in the show king standard: The class is termed Indigo, but includes all patterns of indigo, i.e. check, T-pattern, and barred as well as andalusian ! So wether you have an andalusian, indigo, or indigo bar it will be entered into the indigo class in the show and all these color variations will compete against each other ! Although the homozygous indigo and homozygous andalusians are scarce in number, they should also be entered in the indigo class. Indigo grizzle would be entered in the grizzle classification.
Good luck with your kings, and give indigo a try !
