Sex-linked inheritance and sexual dimorphism

Sex-linked inheritance with sexual colour dimorphism

When talking about sex-linked pigeon colouring in general, the first thing that comes to mind is the Texan. These are not only 'sex-linked' in heredity when mated with other colourings. They also show a sexual dimorphism in colour: male pigeons are lighter coloured than female pigeons. When mated with each other, this sexual dimorphism remains purely hereditary in the strain over the generations.

Crosses of these sex-dimorph Texans with other colourings demonstrate that the responsible hereditary factor 'faded' is located on the sex chromosome: A white or light speckled cock mated upon a blue hen will produce hemizygous females in the slightly lightened female colour, and similarly coloured heterozygous cocks. From the reverse mating, a blue cock with a 'faded' hen, you get females without faded factor and heterozygous cocks in the female colour. Similarly act the dominant stipper gene and the recessive frosty gene, both alleles of faded. Because of the health defects in most homozygous stipper cocks, and their unattractive whitish colouring, the cocks at exhibitions are heterozygous stipper and show the colouring of the hemizygous females. This is also true for Almonds, where cocks of the colour required in the standard are always heterozygous for the stipper gene.

Fig. 1: Sexual dimorphisms at Stipper, Faded, and Frosty. Source: Critical Issues in Pigeon Breeding. What we know and what we believe to know, Part III (2020)

Sex-linked inheritance without colour sexual dimorphism.

Sex-linked inheritance also exists without clear sexual dimorphism due to other hereditary factors located on the sex chromosome. This was discovered earlier than with the stipper and frosty genes. Namely with the recessive hereditary factor 'dilution' and the dominant hereditary factor 'dominant red'. Later also with factors like 'reduced' and 'rubella'.

Homozygous dominant red cocks and hemizygous dominant red female pigeons do not differ noticeably in colour. Sex-linkage is evident in the first cross: from a homozygous blue cock and an ash red hen only blue females and ash red cocks fall, in both sexes, from the reverse mating of a homozygous ash red and only blue females and red cocks.


Fig. 2: Blue cock x dominant red hen and heterozygous ash red son and blue daughter


Fig. 3: Homozygous dominant red cock x blue hen and dominant red progeny, a heterozygous dominant red cock and a hemizygous dominant red hen. Source: Pigeon Genetics 2012, figures 13-16).

Darwin (1868)nknew from French literature (Boitard and Corbié 1824 and Chapuis 1865) that some of the dominant red cocks were distinguished from other red pigeons by black spots after crosses. As was later shown, this is not a sexual dimorphism of dominant red. It is a sign of the heterozygosity of these cocks for black pigment.

Fig. 4: Distinct ‚ink spots‘ in tail and primaries at a heterozygous ash red cock. Source: Pigeon Genetics, fig. 18.


Sex-limited inheritance (coloured sexual dimorphism without sex-linkage).

In sex-limited inheritance, the hereditary factors responsible for a trait are not located on the sex chromosome. They are thus autosomal genes. Male individuals can have the hereditary factors, they are also inherited by the offspring, but they occur almost exclusively in only one sex. When thinking of these characteristics, one first thinks of the decorative plumage and other attributes of the male sex in birds. An example from livestock breeding is the laying performance of females in chickens and that the yield and quality of milk are passed on via the bull, but that the gene can only have an effect in the female sex (http://www.biologie-online.eu/genetik/geschlechtsbegrenzte-vererbung.php).

Direct parallels to this, which have been analysed in more detail, are not to be found in the pigeon literature. In the case of the autosomal factor 'Recessive Opal', in combination with the colour spread factor 'Spread', breeders point out that cocks are usually light silver-grey and hens considerably darker. In the case of the platinum factor, which is also considered to be recessive and autosomal, the cocks differ from the hens already in the bar and check variety on closer inspection. Cocks have a stronger lightening of the primaries and tail feathers than females. If spread is added, the difference becomes even more obvious (Sell 1986, 1994, 2012, 2015).


Fig. 5: Platinum check couple (hen at the left) and Spread Platinum couple with darker hen and light platinum cock

Fig. 6: Spread Platinum (3 cocks and 3 hens) in the 2010th

After the discovery of the factor in the 1960th, the constantly inherited sexual dimorphism in spread platinum remained in breeding for decades. After that, much lighter cocks than in the initial decades and also lighter females suddenly appeared. In these the colour sexual dimorphism was abolished. Even after crosses of platinum with blue homing pigeons, such light-silver-greys were found in some cases in later generations in the last years. Potential causes, which can only be speculated about, are the mutation of the original gene into an allele without this sex-limitation and the occurrence or omission of modifiers by outcrossing upon other colours.

Following the surprising amplifications of sexual dimorphism in the Frosty combinations shown below, it is conceivable that a sex-linked factor with minimal and almost imperceptible sexual dimorphism is also the basis in platinum and may be also in Spread recessive opal. It could be superimposed by the effect of another non-sex-linked factor. If there is such a genetic reaction in frosty-rubella and frosty-grizzle, there could also be analogous reactions in platinum colouration. However, the probability that such a connection had not held so firmly for several decades argues against this. Probably the platinum-coloured ones will have disappeared before the mystery is solved.

Enhancement of sexual dimorphism in sex-linked factors by modifiers: Frosty, Rubella and Grizzle


In this context, observations on the sex-linked frosty factor responsible for sexual dimorphism are noteworthy. Homozygous frosty cocks show a slight colour brightening, similar to that in heterozygous faded. In females it is not or barely visible (see Fig. 1). Rubella is recessive sex-linked. In contrast to the stipper alleles rubella bar and rubella check are not sexually dimorphic.

The combination, Frosty + Rubella, results in almost white appearing silver-grey cocks with sometimes slightly translucent bars or checks.


Fig. 7: Young frosty-rubella cock at the book cover with slightly visible checks and near to white frosty-rubella cock (not Spread!)

Females become ice-grey and the rubella-coloured pattern in rubella pigeons are toned down in colour). The sexual dimorphism of frosty is extremely increased by rubella. In outcrossing upon other colours it is a fragile combination because rubella and frosty are relatively far apart on the sex chromosome and in subsequent matings the linkage can be broken (linkage breakage and crossover).

Fig. 8: Frosty-Rubella couple (left) and Frosty-Rubella hen besides a frosty hen (at the right) Source: Critical Issues in Pigeon Breeding, Part III and V.


Amazing also the effect achieved in Frosty by adding the grizzle gene already in heterozygous state. In hemizygous frosty females the grizzle factor has the same effect as in blue females without the Frosty gene. Grizzles are produced in the intermediate colouration desired in standards. In homozygous 'blue-grounded' frosty cocks' (Fig. 1), whitish white-storked, as obtained in some breeds in homozygous grizzles, are produced. We owe the discovery to Frank Zetzsche during his efforts to rebreed the grizzle colour variety in Thuringian Self (Thüringer Einfarbige).

Fig. 9: Frosty-Grizzle. Hemizygous frosty hen, heterozygous grizzle (left), homozygous frosty cock, heterozygous grizzle (photos and breeder Franz Zetzsche), Source: Critical Issues in Pigeon Breeding Part II (2021)

Didactic aids

If you do not want to take note of the above statements as mere assertions, you will have to deal with genetic basics. With the help of Punnett's squares as a didactic aid, it is easy to understand how sex-linked and sex-dimorphic inheritance occurs. Also, what the combination of hereditary factors can do.

It has been condensed into a booklet with exercises and solutions in English, Dutch and French. On the cover of the supplement to the Introduction to Pigeon Genetics, the mating of a heterozygous stipper cock with a black hen is reproduced in Punnett's square.


Fig. 10: Cover ‘Introduction to Heredity in Pigeons’ and the supplement with exercises


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

Sell, A., Breeding and Inheritance in Pigeon, Hengersberg 1994.

Sell, A., Genetik der Taubenfärbungen, Achim 2015.

Sell, A., Taubenzucht. Möglichkeiten und Grenzen züchterischer Gestaltung, Achim 2019.

Sell, A., Introduction to Heredity in Pigeons, Achim 2022.

Sell, A., Critical Issues in Pigeon Breeding. What we know and what we believe to know Parts I-VI, Achim 2020/2021.

Sell, A., Zucht und Vererbung, Hengersberg 1986.