Understanding Some Basic Ringneck Genetics
This article is written from my meager understanding of the basic genetics of two sex-linked color mutations "fawn and white" found in the Ringneck Dove (Streptopelia risoria). I have no background in the genetics field. My knowledge comes from asking many questions of the known "experts in this field" and by reading the available information directly related to this subject. (ADA Newsletter articles about the Ringneck genetics written by Dr Wilmer J Miller)
DILUTE may be used instead of the term "blonde" (blond) or "fawn" when explaining the reaction it seems to cause in combination with other colors. It is a sex-linked recessive gene because it is found on the sex chromosome and is recessive. I look at the term "dilute" this way: the FAWN color in the Ringneck Dove is the "dilute" of Wild Type (dark) color. You cannot obtain or produce the "fawn" color by breeding a white ringneck to a wild type ringneck or the reverse of this statement.
I can see you already getting that look, thinking this person is wrong. Saying to yourself "I have produced fawn young from a white and wild type ringneck." You may have, but this is only possible if the male parent was wild type (dark) and carried the "fawn" (dilute) gene hidden.
I have been told and have read that the "chromosomes" are different in birds than in mammals. The male has genes on both of the sex chromosome, but the female carries genes only on one chromosome. This is reversed in mammals. I liken it to the following: males have two XX chromosomes and females have one X chromosome. Therefore the male bird can carry the gene for either dilute (fawn) or extreme dilute (white) hidden, but not both. Whereas the female cannot carry either hidden. She is what you see fawn or white.
To remind us of the reversal the bird sex chromosomes are usually called Z and W instead of X and Y. So the males carry two "ZZ" chromosomes and the female carries "ZW" chromosomes with the "W" not carrying any known genes and thus cannot affect anything.
The "Z" chromosomes are unique in that they are the chromosomes that that are most directly involved to determine the "sex" of the bird. To date one cannot look into a fertilized dove egg to see if it contains two "ZZ" chromosomes or just a single "Z" chromosome. If this was possible then the sex of the forthcoming youngster could be seen. I know you are saying; yes this is quite possible with todayís technology! You may be absolutely correct in that this can be done, but the "egg" would have to be destroyed to obtain this information and thus the embryo would not survive and develop.
There are color mutations found on these sex chromosomes which can allow us to determine the sex of the young doves if the male parent is a lighter color than the female parent. FAWN and WHITE are two such colors controlled by genes found on the "Z" chromosomes. In fact, the fawn and white controlling genes are alternatives of each other since they occur at the same "spot" on the chromosome and are called "alleles". Their normal alternative in the wild type (dark) colored dove is a third "allele.
Here goes my understanding of the workings of these two sex-linked genes. I will not talk about any other chromosomes so all relevance is meaning the maleís two "ZZ" chromosomes and the femaleís single "Z" chromosome. Letís stay with the idea that there are no hidden genes in any of the birds until we breed the birds and the resulting offspring may or may not carry hidden genes.
I will be using the terms I am familiar with and have been using for over 25 years. These may or may not fall into everyoneís usage or be the exact terminology to use. If I use the term "purebred" it means nothing more then a bird with no hidden color genes or is not a hybrid and all offspring look just like the parent birds. For example: a purebred wild type is just that; a wild type with no hidden color genes so that it breeds true for the wild type color. You may interpret the term "purebred" any way you want, but for the sake of this article it is used in my context.
Letís assume that one bird is "fawn" in color and it is a male. The following is then true: the gene for the "fawn" color is present on both "Z" chromosomes (remember males have two "ZZ" chromosomes). Letís also assume the mate of the above bird is "fawn" and is a female. The following is then true: the gene for "fawn" is present on the single "Z" chromosome (remember hens only have a single "Z" chromosome). If you breed this male to this female all resulting young will be FAWN and both sexes will be produced.
Letís go on. Take this FAWN male and breed it to a wild type hen. Remember NO HIDDEN color genes are in the parent stock. Although here is where the "sex-linkage" becomes obvious and the first "hidden" color gene occurs. The young produced will be 50/50 in sex and coloration. This 50/50 percentile may not occur in every clutch/nest, but in the end result, Mother Nature will ensure accuracy.
All dark young from this pairing will be males. Males will carry the "fawn" gene hidden. This is because "fawn" is recessive to the wild type color. All "fawn" colored young will be hens. Due to the fact that the "fawn" gene is sex-linked. Therefore the egg received a single fawn gene carrying chromosome and since hens only have a single sex chromosome the result is a fawn hen.
This same scenario can be applied when using a White male to a Wild Type hen. All dark young will be males and carry "white" hidden. All white young will be hens and cannot carry "wild type" hidden.
The above scenario can also be applied when using a White male and a Fawn female. All fawn young will be males and carry the white gene hidden. All white young will be hens because they only receive a single white gene carrying chromosome.
Go to Sex-Linked Chart Line Breeding Chart
In any of the above pairing, excluding the pure fawn pair, young can be sexed when they hatch. Any "pink" or "lighter" skinned young will be hens. In the pair of fawn & white Ringneck the lighter "pink" of the two young will be the hen. Yes, there are coloration differences between the fawn & white youngster and you will be able to see it when they hatch. These differences include the color of the "hatching down" or "hatching hair" of the young. Also the beak (bill) color is another helpful aid in determining the young birdís coloration with the wild type (dark); fawn (dilute dark) and white for the mentioned three colors.
Do any of these pairing work in reverse? NO! If you breed a wild type male to either a fawn or white hen all young will be dark and only the males will carry only the fawn or white gene hidden (never both colors at the same time). Likewise, if you breed a fawn male to a white hen all young will be fawn & only the males will carry the white gene hidden.
I have been working on the Tangerine color mutation the past several years. The first Tangerine hen I got was split to pied. We will not be concerned with this hidden gene now. This Tangerine hen was paired with a known wild type male with the "dilute" gene hidden. The resulting young have been produced (all males are tested for the possible hidden genes): Tangerine, Wild type, Fawn and Orange. All fawn and orange young are hens.
One wild type pied male was produced from an F1 wild type daughter (from the original pair) and a fawn pied male I obtained from the local pet store. This proved that the Tangerine female carried the pied gene hidden & passed it to at least one of her wild type daughters.
Are you still with me? Hope this is catching your attention and getting you into the "genetics" mode.
When breeding Ringnecks with the "dilute" gene hidden one can determine the sex of the young when they hatch. In propagating young from the pair I was working with all "pink or light skinned" young were either "Fawn or Orange". Since I was not interested in the fawn young I did not keep them. I kept the Orange young for test breeding. The dark young would be either Wild Type or Tangerine. I was not interested in the wild type, so I kept the Tangerine young.
I did keep one young male and female wild type (clutch mates); they are used for fostering eggs or young of other species. I have let them raise 6 of their own young and all were wild type (these were disposed of as soon as the color was determined). I have not tested either bird for any other color. They are working as fosters.
I tested the first young Tangerine male to a wild type hen. Each clutch produced two young. The first clutch yielded two wild type young. The second clutch produced a wild type and a Tangerine. The third clutch produced two fawn young. The fourth clutch produced a Tangerine and an Orange. The fifth clutch produced two Orange. This proved the Tangerine male carried "dilute" hidden. I knew the "dilute" was hidden as soon as I saw the first "pink skinned" hatchlings.
I tested the next generation Tangerine male to a wild type hen. To date six young have been raised and only one Tangerine young has been produced. I also tested a Tangerine hen from this same generation with a wild type male. This male was said to be from "purebred" wild type stock. The first six young were three wild types and three Tangerines. The current clutch contained a dark and light skinned young. The light skinned youngster turned out to be an Orange. This proved that the "purebred" wild type male had the "dilute" gene hidden and when combined with Tangerine it diluted it to Orange. Since the "dilute" is sex-linked the Orange is a hen.
With the hatching of the wild type pied, I was stumped as to how this pied bird was produced. I knew that the "pied" gene is recessive to wild type. I consulted with Dr Miller and Gene Hochlan about this bird. Both told me that for the "pied" bird to be produced the hen had to carry the "pied gene" hidden, since the male already showed pied. I no longer had this hen, but had several other wild type hens from the same parents with which to test breed. To date I have not produced another pied using any of these other hens. This was explained by DR Miller, the Tangerine hen had a pied parent or a pied grandparent and she was in the percentage the pied gene was passed to. She then passed the pied gene to a percentage of her offspring.
I will not quote the figures Dr Miller quoted for the percentages; it was very scientific and exact. So I look at it this way. If one of the parents show pied ALL young will receive the "pied gene" hidden. If both parents do not show pied but one carries it hidden then approximately one half of the young can receive the hidden pied gene.
In test breeding the male wild type pied I used a wild type hen. This hen was already tested and did not show to have any hidden genes. To date four young have been produced; first clutch was two "fawn" hens; the second clutch yielded two wild type males. The two "fawn" young were a result of the wild type male pied having a "fawn" pied male parent. The "dilute" (fawn) from the male grandparent bird was passed to his only young & was also hidden. Remember, hens only have a single sex-linked color gene, so the "dilute" gene was given to the egg; hence a Fawn hen.
An interesting note here: these two "fawn" hens are not as light as the other Fawn Ringnecks I have. One needs to look twice to make sure they are looking at "dilute" birds. They are a bit darker. This may be due to the darkness of the wild type color of the birds I am using. I have been told that the colors can be of shade variation, so the color of these two hens is not that critical for this breeding program. All four young do have the "pied" gene hidden though. Plus the two dark males can also carry the "dilute" gene along with the "pied" gene hidden
This article deals with only the "dilute" and one "pied" gene hidden. What if either or both parent birds had multiple hidden color genes, such as Rosy Pied; Ivory, Cream Pied or a number of different color combinations that are possible. It can now get real interesting. One or a combination of two or more hidden colors may influence of the color of the young.
I am fascinated with the Ringneck genetics and the many different colors being produced nowadays. I hope I have piqued your interest in this field. There are many colors yet undetermined as to their inheritance to other colors or how they are created. We as fanciers have the chance to unravel some of the puzzle. Who knows, you may come across a new color.
Dr Miller is probably the best known Ringneck geneticist and has unraveled many of the color mutations already known. The Ringneck Fanciers should not wait for Dr Miller to unravel them all. We as breeders of the Ringneck should be doing our best to procure this data and share it with other fanciers; just as Dr Miller and other Ringneck geneticists have done. If you want to delve into the genetics a bit more and read what Dr Miller has done in this field go to the Internet and visit Dr Millerís web site (DR MILLER)
I wish to "thank" Dr. Wilmer J Miller for taking the time to read, correct any errors I made and his suggestions and contributions to improve this article. I commend Dr. Millerís continued enjoyment of unraveling the color mutations in Streptopelia risoria and other bird species and then sharing his findings with fanciers around the world.