Inheritance of colorations in Pigeons - A Science in Itself

Forum on the 119th Lipsia on December 5, 13:00

Prof. Dr. Axel Sell

Colorations in the early literature and in pigeon standards

The different colorations of the domestic pigeon were stressed still in the works of early writers on ornithology like Gessner 1557. Among the documents of Markus zum Lamm can be found, inter alia, drawings of white, red, black and pied marked pigeon, e.g. saddles and swallows (about 1600). The great German pigeon book from Prütz 1885 contains first standards of pigeon breeds and mentioning of the most common colorations of the breed. The book from Schachtzabel (about 1910) with about 100 color plates of the different breeds and written standards at the backside is a first preliminary standard of pigeon breeds. Though not yet an official standard the enumeration of colorations gets the character of an exclusive sche­dule of colorations allowed in a breed. Since then the former 'Bund Deutscher Geflügelzüchter' (BDG) and today 'Bund Deutscher Rassegeflügelzüchter e.V.' (BDRG) as the head organization in Germany of the four sections responsible for the different kinds of poultry (poultry and water fowl, bantam fowl, pigeons, and finally fancy fowl) claims the right to decide about the colorations within a breed that are allowed to be shown at the exhibitions or not.

Fig. 1: Basic Sources on pigeon colorations

Enumerations of colorations usually start with the most common in a breed and do not follow a genetic order, thus demonstrating that at that time genetic research on pigeons was just at a begin. So there are many inconsistencies and errors that in some cases prevail up to to¬day. Still today the enumeration of coloration does not follow a genetic logic.
Decoding of Pigeon Colorations in the 20th Century
The variety of pigeons colorations must have seemed confusing not only for fanciers but also for scientists who at that time tried to confirm the Mendelian laws in pigeons. Research on pigeons was concentrated at American Universities, but there was an exchange of expe-riences worldwide. The fundamental discoveries were made between 1900 and 1950 and the explorations of details continues. It was a great achievement to get the results in a mindset that could be used for educational purpose. Thank to this is especially Prof. W. F. Hollander from the US, but also genetically interested breeders like Joe Quinn and many other hobby researchers. Key to the success was the early realization that a coloration must be consi¬dered as the result of a combination of genetic factors, which act in a different way to the coloration and genetically are not allelic (alternatives at a specific gene locus), but rather act alongside and with each other.
The didactic preparation
The enumeration of colorations and just beginning with the most common is not a proper start for an explanation of the interdependencies. We will begin with the coloration of the blue bar Rock Pigeons used as reference standard in genetics. At this standard it is possible to show the effect of the numerous mutations that took place in the process of the diversifica¬tion of colorations up to now (Hollander 1983). The basic pigment of the plumage is eumela¬nin (black melanin) with minor parts of phaeomelanin (red melanin). The black bars are caused by higher concentrations of melanin (Haase et al. 1992).
Mutations at the pattern locus
As first mutations with the loss of bars (barless) and the appearance of checks the first two mutations at the so called pattern locus might have happened. More mutations followed. To-day we usually classify barless, bars (the wild-type), checks and T-pattern checks, and more recently dark as a pattern where the checks get so large that the entire shield appears black. The combination of one basic color and 5 pattern results in 5 different colorations, also sepa-rated in the show pen.

Fig. 2: Different pattern at a black color basic

Mendelian Law
With Mendelian Laws we may easily explain the inheritance of the different pattern. Punnett Squares are used to explain the transfer of genes from one generation to the next as a didac-tic tool, and they are helpful in other cases (Sell 2012, 2015).

Fig. 3: Punnett Square for the mating of a barless hen (c//c) and a checker cock (+//+)

In this example a homozygous barless is mated with a homozygous bar, and all of their offspring are heterozygous bars (c//+) with barless (c ) being a recessive. It is important to notice that the barless trait c is still present in the offspring and it is easy to demonstrate in a Punnett Square as well as in the breeding pen, that in the next generation the trait will show up in a quarter of barless young (c//c).

Mutation at the color locus

The coloration of black and blue pigeons is caused by a large overweight of black melanin compared to red. Conversely, it is in the mutation to the red color. A second mutation lead to the appearance of brown that is characterized by an intermediate proportion of black and red pigments. Important for understanding it is to realize that there is no separate pattern for the black, dominant red and brown color. The pattern genes are identical for and in all three colors. If you have understood this, then it will no longer surprise one in breeding practices that a pattern can be transferred from one color to another easily, for dominant genes often by a single cross.

The colors black, ash red and brown usually are named basic colors. The reasons behind might become obvious from the next figure. Black, ash red and brown are the basis of 5 blue/black colorations in different pattern, 5 ash red colorations, and finally 5 brown colora­tions. Adding a further mutation, dilution, black, ash red and brown become the basis of all together 30 colorations in the non-dilute and dilute kind. Thus the term 'basic color' is de­rived from the history of the fancy. It is a didactic term to cover the three main groups of colora­tions in the domestic pigeon. Theemphasis of the basic colors and classification into these three groups is also justified by the fact that the basic colors inter se are inherited sex-linked in a stable way. It is also justified by the fact that every pigeon genetically has a color code even if it is invisible as is the case of white pigeons.

The inheritance of colors can be demonstrated in a similar way as was shown for pattern by a Punnett Square, however adjusted for a sex linked inheritance.

Fig. 4: Combinatorial effect at 3 basic colors and 5 pattern ( 3 x 5 = 15 colorations)

All the colorations enumerated can be mated with each other without any danger of intermin­gling of genes. If we mate e.g. homozygous ash red bar with blue check hens all young will be ash red checks. In the next generation we will get from couples of red checks some blue bar and blue check hens where the dominant red is lost despite their red parents. Mated with blue bars and checks they will not produce any dominant red. Using Punnett squares for the explanation we need one square to follow the inheritance of pattern and a second one for the sex-linked inheritance of color. Finally we have to combine both squares (for the transfer on many other cases see Sell 2007, 2012, 2015).

Mutation Dilution

Dilution was an early mutation that leads to a reduction of melanin in all colorations dis­cussed up to now (Haase et al. 1994). Thus one mutation leads to a doubling of the colora­tions.

Fig. 5: Combinatorial effect for 3 basic colors, 5 pattern und dilute and non-dilute (3 x 5 x 2 =30)

Extension of the 'house of pigeon colorations' in height and width

If you want to extend the concept to the bronze colors typical for many Modena and Modeneser (see the cover at the right in Fig. 1), then you will not experience any duplication, but an extension to 56 colors only. For the ash red color the bronzing cannot clearly show, and at the barless patten the bronze also cannot show up. We get therefore only 26 addi­tional colorations. If we now separate Gazzi (pied marking shown at the cover in Fig. 1 at the right) and Schietti (Non-Pied), then we arrive at 112 colors for Modeneser.

Also an extension upwards is easy to install in the chart. The color spreading factor covers the patterns. The group of blue/blacks (blue barless, etc.) becomes solid black, or solid dun in the dilutes. The group of ash reds becomes monochromatic ashen, and the dilutes mono­chrome cream. The group of brown is uniformly brown, and the dilutes monochrome khaki. The model is 'off and tillable' as a wall unit.

You can still 'put one on it', by involving the recessive red. This factor covers in homozygous state the basic colors and patterns and also the color spreading factor. The non-dilutes reces­sive reds are brown-red, and the dilutes yellow. Finally we can add 'recessive white' that is epistatic in respect to all other traits discussed and cover over all.

Fig. 6: Combinatorial effect at 3 basic colors, 5 patterns, Dilute and non-dilute, Spread, recessive red and recessive white (3 x 5 x 2 = 30 pattern colorations and 9 epistatic ones in addition)

We know for all listed coloration the genetic traits involved. Those are 2 basic colors besides the wild-type, 4 pattern besides the wild-type, dilute and non-dilute, recessive red and non-recessive red and finally recessive white and the wild-type at the recessive white locus. All colorations can be mated together by known rules. The true colorations will be back after such crosses in the first or at least in the following generations. The experienced fancier will recognize heterozygosity at small indicators like ink spots for blue/ash-red cocks.

Molecular genetic findings

It is impressive to see how many research institutions and young scientists today are inter­ested in the research of the domestic pigeon and perform molecular genetic investigations. A recent study that was repeated in several science related magazines was published online in Current Biology by a team that involved researchers from the University of Utah, the Univer­sity of Texas at Arlington, the University of Cincinnati College of Medicine (Ohio) and the Ore­gon Health & Science University in Portland.

The title aptly describes the basic message: Epistatic and Combinatorial Effects of Pigmen­tary Gene Mutations in the Domestic Pigeon. Recessive red in homozygous state covers the basic colors dominant red (BA), black color (+) and brown (b). Recessive red thus acts epistatic (D in Fig. 7). Finally the dilution factor in combination with the three basic colors and recessive red produces an additional set of 4 dilute colors (E, F, G and H in Fig. 7).

Fig. 7: Combinatorial Effect for the three basic colors, recessive red and dilution (Domyan et al. (2014).

Lessons for the practice of licensing?

That the great number of colorations in the domestic pigeon is the result of the combination of relatively few mutations has long been known. Fig. 7 is a detail from the color spectrum of Fig. 6 and a confirmation of the well-known from classical experimental genetics. We know about the epistatic effect of color spreading factor 'Spread', of the recessive red and the reces­sive white and that they can hide different colorations. We know how the patterns are among themselves inherited, as the basic colors relate to each other, as diluted and non-di­luted are inherited, recessive red and recessive white.

On this basis you can consider all colorations as 'intermediate' colorations that can be syste­matic bred of existing colors again if one of them should be missing. The only requirement is that the relevant traits of the specific color code are present in the race. Anyone who has a little concerned with the genetic basis of pigeons coloring should know that you get the dun coloration e.g. in the first generation when mating a dilute blue cock and a black hen.

Rezessiv Gelb x Schwarz = Dun

Why these still need a license by the recognition process for 'new colorations' as at this exhibitions the Chinese Owls in the 'new varieties class', is inexplicable. Stargard Shaker e.g. are not a standard color and to become one they would have to go also through a complicated and costly 'licensing procedure'. Though every experienced fancier knows and everybody else could know that some dun are produced by mating the standard colorations yellow cock and black hen in the first round.

It is occupational therapy for the staff involved in recognition committees and on top of that costs or a 'taxation' for the fanciers. In the business world, one would speak of an abuse of a monopoly situation. Maybe it's time after molecular genetic investigations confirmed the combinatorial effects for recognition of the 'intermediate' colors of traits present in a breed as a general rule.

Inheritance of pigeon coloration - A science in itself?

From the perspective of a layman the breeding of pigeons of different colorations appears like an unpredictable endeavor. However, the genetics of pigeons colorations is based on facts that can be checked by everyone. From classical investigations the genetic codes of the most important colorations are well known, and the basics of these findings now are confirmed by molecular genetic investigation. The knowledge about the genetic basis enables the fancier to mate the different colorations of a breed in a reasonable way. That is 'applied genetics' in pigeon breeding, and has parallels in other animal species. That does not exclude that there are still many questions that have to be answered yet. Pigeon genetics is not at an end and fanciers can help to analyze some of the mysteries.

Literature

Domyan et al. (2014), Epistatic and Combinatorial Effects of Pigmentary Gene Mutations in the Domestic Pigeon, Current Biology, http://dx.doi.org/10.1016/j.cub. 2014.01.020.

Haase, E., S. Ito, A. Sell and K. Wakamatsu (1992), Melanin Concentrations in Feathers from Wild and Domestic Pigeons. Journal of Heredity, Vol. 83 (1), pp. 64-67.

Hollander, W.F. (1983), Origins and Excursions in Pigeon Genetic, Burrton , Kansas 1983.

Quinn, J. W. (1971), The Pigeon Breeder's Notebook. An introduction to pigeon science, Atwa­ter, Ohio.

Sell, Axel und Jana (2005), Taubenfärbungen. Colorations in the Domestic Pigeon, Oertel & Spörer, Reutlingen.

Sell, Axel und Jana (2007), Vererbung bei Tauben. Oertel & Spörer, 2. Auflage, Reutlingen.

Sell, Axel (2015), Genetik der Taubenfärbungen, Achim 2015.

Sell, Axel (2012), Pigeon Genetics, Achim.

35 years 'Applied Pigeon Genetics'