Blue is not blue: smoky blue, dirty blue and variants in the domestic pigeons

A study by the University of Texas (Krishnan / Cryberg 2020) sheds new light on the genetics of the variants of the blue pigeon coloring. In pigeon breeds, the color range extends from a delicate ice blue for ice pigeons and damascene pigeons, a light blue for Hamburg tumbler breeds, and the light gray pigeon blue adopted from the rock pigeon, to a dark 'strong blue' for Vienna Tumblers and related high-flyer breeds.

To the history:

In the variants deviating into the dark, there are those with light beaks that lack the otherwise existing white edged outer fane in the tail. They are also available with dark beaks, mostly in the standard with dark blue to black eye cere and with dark legs in the first weeks. The Dutchman Bol had already investigated the second variant in 1926 when analyzing the racing homer colors and determined the dominant inheritance. 'Vetkleur' ​​(strong color), adopted in English as dirty, with the genetic symbol V.

Fig. 1: Dirty (Vetkleur) and the wild-type at Racing Homer. Source: Bol 1926

The variant with a light beak was analysed by W.F. Hollander in the 1930s with the result of a recessive inheritance in mating with the wild type (Hollander 1938). As a symbol, sy was designated for smoky.

Variants of the blue color in the sub-groups:

In breeding, the varieties in fancy pigeon breeding have little contact. In some breeds the color of the wild type with a dark beak was desired, in others the light beak, and in others very dark blue pigeons with very dark beaks. In the case of homing pigeons, in which all three variants occur, the coloring is irrelevant anyway. However, there were discussions about the correct color in some special clubs due to the large range of colors shown in Fig. 2 and 3, both in the class of dirty as in the class of those of smoky blue. Due to the color differences within the groups, it was early assumed that there were alternative genes (alleles) for variants of smoky as well as more alternative genes of dirty with a similar but not identical phenotype. This proposition can also be found in the most recent study of this question from the University of Texas for dirty, although the molecular genetic location of the V variants are not lined out in the paper.


Fig. 2: Dirty Blue: Vienna Highflyer blue bar (Jens Passeker) and Budaer Blue (Fred Wohlgemuth). Source: Sell, Pigeon Genetics. Applied Genetics in the Domestic Pigeon, Achim 2012.


Fig. 3: Smoky-Blue at Memel Highflyer (Werner Rahlfs) and East Prussia Tumbler (Hans Falk). Source: Sell, Genetik der Taubenfärbungen, Achim 2015 (German language).


Fig. 4: Smoky Blue Racing Homer with a rather dark beak as adult found in many smoky Racing Homers as well as the clouding in the shield. At the right a rather dark smoky Stargard Shaker (Kai Schnellbächer). Source: Genetik der Taubenfärbungen, Achim 2015.

Conjectures about Dirty and Smoky's genetic connections:

Systematic studies on the genetic connections of dirty and smoky and possible alleles are missing. Some genetic interested fanciers were satisfied with the indication that there could be alternative expressions of the genes in question in both groups with slightly different effects, so that there would exist alleles. Differences can also result from the action of other (modifying) genes. Dirty and Smoky for themselves can be seen as modifiers of the blue color and can experience additional color changes due to additional factors acting as modifiers. From this point of view, dirty could also be seen as an additional modifying factor for smoky blues or - the other way round - smoky as a modifier for dirty blue. This last hypothesis of side-by-side independent factors has now been refuted by researchers from Texas (Krishnan, Cryberg 2020) at least for the Smoky and Dirty variants they tested. Thankfully, pigeons from the strain used for testing are also shown so that you can see which variants have been tested.

Fig. 5: Dirty, Smoky and the wild-type in der Investigation of the University Texas (from left to right). Source: Shreyas Krishnan, Richard L. Cryberg 2020


For the test:

The authors evaluated DNA data from existing pigeon families, in which peculiarities were found in some individuals due to deletions in areas which, according to the findings, were also responsible for coding the coloration in other species. The phenotypic examination identified these as smoky when examining two close bred families. The recessive inheritance known for Smoky from ‘classical genetics’ that follows the Mendelian rules could be followed with DNA analyzes. The individuals in the families were all phenotypically either dirty or smoky.

The following test was carried out in the traditional way first to get some answers at hypothesis 1.

Hypothesis 1:

Available for tests were smoky blues, from which it was assumed from the family tree that they were also dirty. Coupled with a partner with the wild type, all young should be at independent inheritance of dirty and smoky due to the dominance of V dirty, unless the partner happens to be heterozygous smoky.

At the first crossing, at independent hereditary factors, all young would be heterozygous dirty and thus dirty-colored because of the dominance of V. They would also be split for Smoky, which would have no effect due to the recessiveness. However, if the selected partner happens to be heterozygous for Smoky, which cannot be seen because of the recessiveness, then 50% of the young according to Mendel would be homozygous Smoky and the other 50% heterozygous. Based on the experience gained in the test, the young homozygous smoky under the hypothesis of independent factors should cover V epistatically. In that case 50% dirty and 50% smoky would be expected, none individuals with the wild-type.

The result was something completely different. Coincidentally, the partner was actually mixed for Smoky. 3 of 9 young were smoky-blue. The remaining 6, however, were not dirty, which they should have been according to the epistatic model, they corresponded to the wild type. The conclusion drawn from the result that the epistatic model should be rejected and hypothesis 2 tested.

Hypothesis 2:

A model that is compatible with the results of the pairing is the idea that Smoky and Dirty are located at the same location at the relevant chromosome and are therefore alleles in genetic terms. Pigeons can then be pure Smoky (sy // sy), pure Dirty (V // V), mixed for each of the factors (sy // V). In addition, of course, also mixed with regard to the wild type (sy // + and V // +) and also wild type (+ // +).

The homozygous Smoky pigeons chosen for the test was genetically characterized by sy // sy. A partner from an unrelated strain that is mixed-smoky is sy // +. Dirty (V) does not appear in either of the hereditary formulas and therefore not in the offspring either. Only homozygous smoky (sy // sy) and heterozygous smoky (sy // +) are to be expected. Hypotheses obtained from empirical observations should be usually empirically confirmed by independent series of tests, which can be easily made up for by breeders in their own stock given the simple experimental arrangement shown by the authors.

Modifications by additional color factors:

The factors dirty and smoky, in conjunction with other hereditary factors, also cause typical changes that have been systematically compiled (Sell 2006) and are shown below using the examples for dominant red. In combination with the ice factor, dirty (for ice pigeons and damascene) and smoky (for some Tumbler breeds) have typical effects that allow to identify the traits also in these combinations.


Fig. 5: Dirty (at the left chart) and Smoky ash red bar Pomeranian Eye Crested Highflyer compared to the wild-type ash red bar at a Danzig Highflyer: Source: Genetik der Taubenfärbungen 2015 and ‚Pigeon Genetics 2012.

Experimental arrangement for testing your own variants:

Tests can be carried out in the traditional way by pairing pigeons with any colors that are homozygous Dirty in one bird and homozygous Smoky in the other, and both should come from a strain from long-term pure breeding, so that no other recessive hereditary factors disturb the picture. Assuming the validity of the hypothesis of the allelic relationship, a first cross between Dirty and Smoky in the Punnett square can be represented as follows:












All hatchlings are phenotypically dirty, but heterozygous Smoky. When the young are mated to one another, the picture becomes more varied.

Splitting the 1st generation to generate the F2











There are dirty, homozygous smoky and besides for dirty and smoky heterozygous individuals. From the phenotype there are about a quarter smoky and three quarters dirty. Three quarters, because due to the dominance of dirty, it is not possible to differentiate between pure and mixed animals. We will not raise any wild type individual.

We may compare the results with the potential outcome at hypothesis 1. According to this model of two factors acting in parallel, in addition to the majority of dirty and a quarter smoky, 3/16 young individuals of the wild type would also be expected. If an animal is raised that clearly corresponds to the wild type (not smoky and not dirty), then the tested variants are something else, the hypothesis would have failed for these variants.

In principle, a breeder can carry out the test with all color variants that he knows are homozygous for Dirty or Sooty. Jokers should not, however, choose recessive red, yellow or the diluted blue color or dilutes in general, as these colors have a light beak even without smoky. Pieds can also cause problems for the later classification of the young.


Fig. 6: Mating of a Dirty check Ice Pigeon cock and an Ash Red hen with an ash red young cock and a black hen with dirty beak and some black at the legs as indicator for Dirty.

The first part of a possible test was by accident, and not related to the issue dealt with here, completed at the same time as the report. For that purpose colors that are easier to classify would have been used. A black check ice pigeon cock with the dirty factor, paired with a Spread Ash Pomeranian with the smoky factor, resulted in two young that were clearly phenotypically identifiable as dirty. Gender-bound, and also easy to understand in Punnetts squares, a Spread-Ash-colored cock with ink spots in tail and primaries as a sign that he is heterozygous black, and a black hen with a dark beak and slightly darkened legs.

In the F2 according to the allelic model there should be no wild-type young among the now colorful flock. There will be dominant red and black young in both sexes, some black, some ashen, but also some blue check and ash red check, and some of them will remember the grandfather's ice factor.


With their study, Shreyas Krishnan and Richard L. Cryberg showed how molecular genetic studies and classic genetic inheritance tests can be combined with benefits. The examined pigeon families with the dirty and smoky factors were shown to behave like alleles and not like independent hereditary factors when inherited as was believed up to now. That would mean in consequence also an adaption of symbols. The test procedure they have shown can easily be traced in two generations by genetically interested breeders for other strains and possibly other variants. Yet unanswered are the causes behind the differences in the depths of color in both groups.


Bol, C.J.A.C., Genetic analysis of kleuren, veerpatronen, ink, en afteenkenigen bij postduiven. Genetica 8: pp. 45-154.

Hollander, W.F., Inheritance of Certain “Blue-Black’ Patterns and “Bleached” Colorations in the Domestic Pigeon. Genetics 23 (1938), pp. 12-27.

Krishnan, Shreyas * and Richard L. Cryberg, Department of Biology, University of Texas at Arlington, Arlington, Texas, 76019, Effects of mutations in pigeon Mc1r implicate an expanded plumage color patterning regulatory network, 2020, bioRxiv preprint doi: https: / /doi.org/10.1101/792945. The copyright holder for this preprint (which was not peer-reviewed) is the author / funder. It is made available under a CC-BY-NC-ND 4.0 International license.

Sell, Axel and Jana Sell, Taubenfärbungen, Colourations in the Domestic Pigeon, Les couleurs des pigeons, Reutlingen 2006.

Sell, Axel, Genetik der Taubenfärbungen, Achim 2012.

Sell, Axel, Pigeon Genetics. Applied Genetics in the Domestic Pigeon, Achim 2012.