Isabell in pigeons and breeding success with guided mate choice

Isabella in old literature

Isabell coloured pigeons are already mentioned in old literature as a speciality. Neumeister mentions them in pouter pigeons in 1837. Coloured drawings promoting the colour scheme are first found in pigeon books in England. Thus, in Tegetmeier 1868 a muffed pair. The coloured drawing in Fulton 1876 is clearly recognisable as a pouter pigeon. The delicate colour of the Isabella is emphasised by the adjacent red and yellow in comparison.


Fig. 1: Isabella pigeons at Tegetmeier 1868 and Fulton 1876

The muffed Isabella Pigeons are named differently in old literature, sometimes as Dutch, sometimes as Saxon Pouters.

Prütz 1885 shows a clean-legged Brunner Pouter. Behind it in the drawing a black with white bars. Isabella are often shown in drawings together with other white-barred ones, as in Fulton's work. However, the colourations and white bars are genetically based on different hereditary factors. The fact that they were often shown together in the picture did not make it easier for the breeders and later also not for the decoding of the genetic structure.


Fig. 2: Isabell-coloured Brunner Pouter and isabell-coloured Prague Tumbler at Prütz 1885. In the background a light blue with white bars.

In Prütz's work, next to the Prague isabell-coloured Tumbler, a light blue with white bars, which is not quite realistic. Genetically, like the Isabella, it has the hereditary factor Dominant Opal (Sell 2012, 149-155). The tail bar of the light blue in reality is bleached to a lighter whitish colour, different from the drawing.

Breeding problems with Isabella

Despite all the praise, there have always been only a few breeders of Isabella. This may also be due to ignorance of how to breed this colouring best. Until the 1960s, however, the breeders did not mention any breeding problems with Isabella and also not of light blues with white bars, checks or lacing, which are linked to them by the common hereditary factor Dominant Opal. Then there were reports from breeders about poor breeding results. They suspected inbreeding or diseases as the cause. In the genetics group around W.F. Hollander in the USA there were notes in the 'Pigeon Genetics Newsletter' published by him around that time that it was difficult to obtain purebred Dominant Opals. And if you had an animal that could be homozygous, there would be vitality problems.

Andreas Leiß from Vienna succeeded in breeding such purebreds in feral pigeons. He documented them in photos and also showed the problems of the surviving pure-bred Dominant Opal. Whitish/grey in colour, not attractive and vitality problems. The reared female died after a short time, the juvenile cock lived a little longer but did not reproduce. This matched other reports of grey/white juveniles already dying in the nest.

Investigation into the reproduction of isabella

It is the merit of Wolfgang Schreiber and his breeding friends of the Brno and Saxon Croppers to have investigated the thesis of the failure of the pure dominant opal on a broad data basis. The results confirmed the earlier assumptions on the lethal or semi-lethal effect of homozygosity for Dominant Opal (Schreiber 2004). It was found that from pairs of two isabell-coloured pigeons (648 eggs) on average 3.2 young were born, from mixed pairs (665 eggs) 5.2. This could be broken down into a lower number of eggs laid per pair and lower fertilisation rates in pairs formed by two isabella, lower hatching rates from the fertilised eggs and higher mortality rates after hatching before banding (see also Sell 2012).

From Punnett's squares one can read that half of Isabell x Yellow are expected to be isabell-coloured. That is 2.6 isabella per pair from 5.2 kittens. From Isabell x Isabell with 3.2 kittens there are arithmetically just under 2.2 isabella per pair. In percentage terms it is more, but in absolute terms it is less than in the comparison pairing.


Fig. 3: Brunner Pouter yellow (complementary color to isabell. Brunner Pouter isabell (Günter Dietze) and Saxon Pouter isabell (Dieter Geisemeyer). Source: Sell, Pigeon Genetics, 2012, photos: Layne Gardner

Instead of yellows, one can also mate with reds as a complementary colour, if possibly the colouration is also somewhat darker. Spotted bills are sometimes mentioned as a disadvantage. Epistatically masked, the reds and yellows should genetically possess the bar pattern.

Change in the proportion of isabella in the stock without selection in the case of random mate choice

Lethal genes are quickly lost in nature. This would also happen to a strain of isabella or light blue pigeons left to itself. If the breeding stock for the next breeding period is completely replaced by the offspring, this can be made plausible in fast motion by simple model considerations. Let's start with a flock of pairs Isabell x non-Isabell (100% heterozygous Dominant Opal). Directly readable in Punnett's square, a quarter of the kittens do not have the factor. Half of the kittens are heterozygous Dominant Opal like their parents. A quarter of the kittens are homozygous Dominant Opal. These die already in the egg or shortly after hatching. With random selection from the young of the year for further breeding, the percentage of Dominant Opal will have dropped from 100% of the stock to 66.6%.

When these offspring mate with each other, three combinations are conceivable. Non-carriers of Dominant Opal with each other (1/9 of matings), mixed carriers of the gene with each other (4/9 of matings) and a carrier of the gene with a non-carrier (4/9). Failure by purebred Dominant Opal will occur in these matings when two trait carriers mate with each other. If the reproductive behaviour is not influenced by other confounding factors, the proportion of reproductive Dominant Opals will be reduced to 50% in this cohort. If one follows the model's calculation instruction over the generations, the proportion thins out further to 40%, 33.3%, 29%, etc. (cf. Fig. 4).


Fig. 4: Model observation of the percentage of heterozygous Dominant Opals with random mate selection over the generations. Exchange of parents by offspring after each breeding year.

Stable ratio of 50% of heterozygous individuals in the wild White-throated Sparrow due to sexual preference for differently coloured mates (negative disassorting mating)

It is interesting to look for parallels with other animal species. Frank Mosca recently pointed to studies in the American White-throated Sparrow (Zonotrichia albicollis). Here, too, there is a dominant inheritance of the colour variant 'white' over 'tan', the other variant. By 'white' is meant that the throat patch and a line above the eye and over the head appear white and not brownish (tan) (cf. Fig. 5). Here, too, the gene that is considered dominant seems to reduce vitality in the case of pure heredity, according to the observations. Why do they still exist, and stable in the population by 50%?

Fig. 5: White-throated Sparrow, the 'White' variety with white instead of brown (tan) markings. Source: https://de.wikipedia.org/wiki/Wei%C3%9Fkehlammer#/media/Datei:Zonotrichia_albicollis_CT1.jpg

According to observations on mate choice, mating of white x tan and vice versa occurred almost exclusively in free-living populations. As recommended for Dominant Opal in pigeons: Isabell x Yellow and vice versa. The other matings occurred in the 1 percent range. These few pairings probably triggered by the absence of other partners. As with species crosses between domestic and wild pigeons or doves, there provoked by the keeper. Pure-bred 'whites' were therefore hardly found in nature, 3 out of 1,989 birds, one male and two females. The male remained smaller than normal (Hedrick, Tuttle, Gonser 2018).

In feral domestic pigeons, Johnston and Johnson (1989) had reported preferences for certain and also different from the own colourations in mate choice (negative assortative mating), but nowhere near as clearly as in the White-throated Sparrow. The molecular genetic difference between Tan and White was found to be chromosomal inversions involving about 1000 genes on the white-chromosome, with genes affecting not only colouration but also other characteristics such as behaviour (ibid.). Thus, whites and tans are differently aggressive, they also differ in brood care. Among the genes in this area, presumably also those that directly or indirectly influence mate choice.

Reactions to lethal genes in pigeon breeding

According to the breeding recommendations for pigeons, in the case of genes with lethal or semi-lethal effects, two trait carriers should not be mated with each other, also from the point of view of animal welfare. The reasons can be seen from the above. In nature, in some cases, negative assortative mate choice ensures that the heterogeneity of the initial stock is maintained over the generations. In pigeon breeding this is simulated by guided matings. The question of whether there is a natural affinity for divergent coloured mates in dominant opal-coloured pigeons - similar to the White-Throated Sparrow - does not seem to have been asked yet. Whether preferences are signalled by colouration or by other associated traits remains to be seen. Whether it is better to speak of recessive or dominant can also be left open for Dominant Opal. Historically, dominance is spoken of on the basis of colouration. If the mortality of the young is put in the foreground, the effect is recessive.


Hedrick, Ph. W., Elaina M. Tuttle, and Rusty A. Gonser, Negative-Assortative Mating in the White-Throated Sparrow. Journal of Heredity, 2018, 223–231.

Hollander, W.F. (Hrsg.), Pigeon Genetics Newsletter, Volume 1962.

Johnston RF, Johnson SG. 1989. Nonrandom mating in feral pigeons. Condor. 91:23–29.

Schreiber, Wolfgang, Erhebung über die Nachzucht isabeller Brünner. Brünner aktuell 2004, 49.

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