WHITE
If you think think Ash-red and recessive red are confusing? If you think the bronzes will drive you crazy? You ain't seen nothing yet! This time, it's white. Let's get something straight right off the bat. WHITE IS NOT A COLOR!!! I can hear the screams now, but the reason we say that is because there's no melanin present in white feathers. Melanin is the pigment which is normally in a pigeon's feathers and which provides the colors we see depending on its shape and amount. In the case of white, what happens is that this melanin is not put into the feather. There are various times during the devolpment of the embryo or squeaker where pigment synthesis (production) can be interferred with. Either the melanin is never produced or it doesn't get placed into the feather of the bird. What happens then is that the feather grows normally, but, without melanin available to color it, only a white feather is produced. The white, itself, is a result of light hitting the feather and being bounced back to our eyes. Since none of the various light rays are absorbed by the melanin, all of them are bounced back and we see the combination of them as white. White bird Photos
Let's assume that we have a bird which is genetically Ash-red Check. In the normal course of events, that is the pigeon we would see. Now let's also assume that this particular red-check also carries in its genetic code some other information which stops its body from producing the type of melanin (phaeomelanin) which it normally would. We've found such a mutation. We call if recessive white (genetic symbol z). Remember, recessive traits normally need two genes carrying that information to be in any one bird in order for the bird's cells to follow the directions that information dictates. So now we have an ash-red check bird which carries information for no melanin production. Because no (phaeo) melanin is produced, none is put into the growing feathers. A white pigeon is the result.
Now let's suppose we have a bird which is genetically Andalusian. (Spread heterozygous Indigo). Let's suppose that this bird, too, carries two doses of the information for recessive white in its genotype. When it feathers out in the nest, it will also be a pure white pigeon, identical in feather color to the ash-red check bird mentioned above. In like manner, we can have any pigeon, no matter what color it would normally be, carrying information which prevents melanin from being placed into the feathers. In every case, such a bird will be a white pigeon. That means a white bird can literally be almost anything genetically underneath those white feathers. It could be a blue-bar, a red check, a recessive red, a reduced T-pattern blue check, etc. If we wish to know what color is hidden by the bird's inability to place the melanin in its feathers, we can mate the white pigeon we're testing to a blue bar. If the blue isn't carrying recessive white, all the young produced will be heterozygous (have one gene only) for that particular trait.. That means their bodies will go back to using the normal information for pigment placement. The youngsters will feather and color normally. If we rear enough youngsters, We can determine from that which color the white parent has been hiding under its white feathers.
Okay, that recessive white mutation is one way we can get a white pigeon. There are other ways too. One is sort of a two or three step process which winds up with almost the same results. Let's consider an Ash-red bird not carrying recessive white. Remember, in Ash-reds, tail feathers (retrices) and flight feathers (remiges) are washed out to an ashy-gray color. The pigment production in those feathers has been interfered with by the Ash-red mutation so we don't get the nice, dark flights and tail of a wild-type pigeon. Now think of a blue stork-marked bird (I'm using stork-marked as in Budapests and tumblers and not as it's used in Color Pigeons.) Here we have a pigeon with two doses of grizzle. Grizzle also interferes with pigment production, but not to the extent recessive white does. Rather, the grizzle mutation sort of tosses the melanin out in stages. With one dose of it, we get a salt and pepper look, the classic grizzle of the Dragoon. If the bird happens to be homozygous for grizzle (carrying two doses of grizzle), however, then much more of the pigment is kept from forming and what we get is a bird mostly white over its body but with some pigment production on wing tips and tail tips - the stork marking.
Let's combine both ash-red and two doses of grizzle in the same bird. (Some of you are already ahead of me, aren't you?) The grizzle mutation cuts melanin production on the bird's body plumage, while the ash-red mutation not only cuts it there, but, more importantly for our discussion, also cuts it on the wings and tails. What we have now is a bird whose pigment production is practically zero. With no pigment being produced to sit in the feathers, the bird appears white. One difference between this white phenotype (how the bird appears to us physically) and a recessive white phenotype is the eyes. In the recessive white bird, the eyes are bull (dark-colored). In the white produced by combining Ash-red and Grizzle, the eyes are often (though not necessarily) colored.
There are other mutations which interfere with pigment production. We can combine such depigmenting mutations so that their interference is additive and less and less pigment is produced and we can raise whites. A combination of homozygous indigo and Spread produces a near-white phenotype, though in this case the head is often still dark. By choosing certain mutations, we can also make our stock look better than it may actually be. Those Ash-red Grizzle whites, e.g., often have foul-feathering which can be made less visible if we include dilution in the mix. Ash-yellow is a lot less conspicuous than Ash-red.
What about patterned birds? The Magpies, Swallows, Gazzis, and so on? These patterns are under genetic control. In these cases, the mutations involved interfere with pigment production or placement only in selected areas of the bird's plumage. Perhaps, the production interference happens during day seven of incubation or during the travels of the melanin to its normal feather home. Some of these pattern white mutations appears to be alleles (alternate choices for the same place on a chromosome). Some brief testing in my own loft a few years back indicates that swallow marking and Baldhead marking are such alleles. There is still much more testing to be done to verify or refute this, as well as to determine the inheritance of the dozens of pattern white mutations. Some, such as the Lahore marking, are apparently the combination of a few different patterns into the same bird and because of selection, they appear to us to be one marking.
So what about splashes? (Birds which have no pattern to the white in their feathers.) I believe what we're seeing is the interaction of different alleles in the same bird. When I crossed Baldhead and swallow, I got mostly white youngsters with colored marking only on top of the body. Other crosses of different types which I've seen, e.g., gazzi and swallow also gave heavily splashed birds. There may be other reasons for splashes also. There's still much we need to learn about the genetics of white in pigeons. Perhaps data from your loft will provide the answers.
ADDENDUM - July 2021: Drew Lobenstein told me that he and John DeCarlo, Jr. have some evidence that the white in Cumulets is actually produced by two separate grizzle factors working together. They are calling them "Splashy Grizzle and Powdery Grizzle" right now.
Copyright 1997 by Frank Mosca. This work may be downloaded or copied for non-commercial individual use only. All other rights under copyright are retained by the author.