There are four pigeon patterns. Barless (c), Bar (C + ), Checker (C), and T-pattern Checker (C T ). I have the patterns listed from left to right in order of dominance with barless being at the bottom. Click on each picture to enlarge them.
The examples above are given for the blue series, but patterns can also be seen with other mutants like ash-red, brown, hetero indigo, hetero grizzles, milky, dilute, pale, reduced, extreme dilute (lemon), frill stencil, toy stencil, ice, recessive and dominant opal, all heterozygous and hemizygous almond series, dirty, etc. The pattern is located in the c locus. and therefore represented using the letter c and inherited independently of feather color mutations.
I have mentioned the word wild-type in almost every page so far, because it is a very important concept to understand when studying the inheritance of traits. In the pattern series, the bar pattern has been chosen as the wild-type but many people in the past and even today still argue about which pattern should be the wild-type; check or bar. Once the earlier scientists agreed on Columba livia to be the ancestor of modern breeds of pigeons, Darwin believed the barred type to be the original, while checked birds were probably due to “the extension of these black marks (black bars) to other parts of the plumage” (Darwin 1868, vol. 1, p. 183). Another scientist, Whitman suggested that the barred type resulted from a gradual clearing of the wings of checks “from before backwards” (Whitman 1919, vol. 1, p. 19), until the two- barred type resulted. Rock Pigeons display many variations among their numbers scattered throughout the world but the argument rages on yet, as to whether the earliest forms were barred or checkered. There is no reason at all for a student of pigeon genetics to get into the chicken or the egg causality dilemma, commonly stated as "which came first, the chicken or the egg?" The standard is chosen and what most of us don’t realize is that the standard doesn’t have to be the most dominant. When studying genetics we choose a standard because it allows two people to talk about genetics without wasting all of their time defining the standard they are using every time they talk to a new person. So, it doesn’t matter which pattern was chosen as the wild-type. Gmelin (1789), who was the first person to report and describe Columba livia, choose this phenotype, and consequently the genotype became the wild-type in pigeons. However, once the phenotype for wild-type is chosen, we can not change it; otherwise, we would have to test everything to this new wild-type phenotype.
The top dominant of the pattern series is called the T-pattern checker (gene symbol C T ) where a few light edges or triangles as "check" in the wing shield area are visible. T-Pattern check gets its name from the small light colored T in the check pattern of their wing shield feathers which can range from the wing shields showing light colored "T"s on each feather, to having the whole wing look like black. Thus, the common names of this pattern among pigeon fanciers are "velvet", or "blue-tailed black" (See picture on the right). It is also important to note that the T-pattern check phenotype with the help of darkening factors like sooty, dirty, and smoky can easily be confused with a spread phenotype. However, spread is a different mutation located on a different locus and therefore is not part of the pattern series. Unlike spread mutation, the T-pattern check birds have regular flight and tail feathers with the sub-terminal tail band, and albescent strip. In addition, T pattern check birds, just like the rest of the pattern series, might have colored or white rumps where the spread mutation would normally cover the rump feathers. Spread is known to be epistatic to pattern series, therefore when there is a spread gene present in the genotype, it suppresses the effects of pattern and make the pattern not visible in the phenotype.
In this page, the pattern phenotypes of the blue series are listed in the order of their progressive decreasing amount of black in relation to blue, and it is very interesting that they appear to be epistatic in their hereditary manifestation in the same order, i.e. each to the one that follows. However, when we describe the relationship between the allelic genes, we used the words like dominant, recessive and co-dominant, and use the word epistatic when we describe the relationship between non-allelic genes.
In the pattern allelic series, recessive to the T-pattern check is called checker or check ( gene symbol C ), showing several triangular checks of light gray or "blue" in the blacker wing shield area (See picture on the left). The word check originates from the so-called checked appearance of the wing. This condition is caused by the presence of two black marks situated respectively in the inner and outer vanes of the wing coverts, the central and proximal portions of which are blue. The rest of the plumage of checked birds is blue with the invariable exception of a black terminal band on the tail and of the not infrequent presence of checks on the upper back. The rump may be either very light, almost white, or a shade of blue uniform with that of the wing coverts, or any shade between these two colors. According to Sarah van Hoosen Jones (1921), somewhat similar checked patterns are found in Columba guinea and many of the doves (mourning doves, ground doves, etc.); in fact a large number of the individuals of the order Columbae exhibit check pattern. The genetic behavior of the checks of Columba livia and of the doves are probably caused by the analogous mutation at the same spot on the chromosome. Since all Columbae are related evolutionarily, major parts of their genomes expected to be identical.
It seems the wing bars on checker pattern are usually wider than the barred birds when some checkers show the wing-bars while some do not. The T-pattern check, check and the bar patterns actually intergraded, possibly from modifying factors or more likely from intermediate alleles. According to Hollander, the checker pattern has been subdivided according to the amount of spreading into several sub-types. Thus, Hollander identified two additional checks in the pattern series: dark checker ( C D ) which comes inbetween T-pattern check and check, and the light checker ( C L ), which comes inbetween check and bar patterns. I will purposely neglect these additional pattern alleles for the time being, because not much is known or reported about them. It seems for an allelic series like pattern to have many different phenotypes, where we know of at least six alleles might be caused by not genes and very likely with a large dose of epigenetics. Nevertheless, one can almost always distinguish these different check patterns in pigeons.
The wild-type ( C + ) gene in this allelic series produces the bar pattern. where the barred bird has two very distinct bars across the distal end of the wings. Recall that bar pattern is our standard and therefore represented with a plus sign ( + ). Both T-check and check alleles are dominant to wild-type (bar pattern). Although this wing pattern is also seen in many other mutant colors (ash-red, brown, indigo, opal, etc.), in pigeon genetics “Bar” refers to the pattern commonly called “blue-bar” in the blue series. The wing shields of a barred bird are blue with two transverse black wing bars, one of which extends through the tertiaries and innermost secondaries, while the second extends through most of the secondary coverts. In a bar phenotype, the tail and rump are similar to those of the check, but the rump is free from any check marks. According to Hollander there are smooth and coarse spread areas found in the feathers of pigeons. Smooth simply describes the smooth color transition seen on going from the blue area of the tail feather to the black area of the tail bar. This transition is a smooth gradation and can easily be seen by the naked eye, which is the tiny area that is neither black nor blue right on the edge of the tail bar. The word “spread” used here should not be confused with the spread mutation ( S ) but the sub-terminal tail bar is described as smooth spread by Holllander. The coarse spread on the other hand is once again the name chosen by Hollander to describe the appearance of the tiny transition region between blue part of the feather and black part of the pattern. This transition does not happen smoothly as it does with the tail bar. Rather, the pigment in the transition area is distributed such that there are dark specks surrounded by lighter areas. Thus, this transition region has a grainy naked eye look to it which Hollander properly described as coarse.
Cole and Hollander were convinced that the pigment which provides the coloring matter in our birds’ plumage, came in two different arrangements. In the bars, pigment was spread out. In the rest of the feather it was clumped. They thought when the black pigment
is clumped together in the cells of the feathers, it refracts the light in such a way that we see a bluish tinge as in wing shield of the blue bars. Cole in 1914 claimed that the granules in the barbules of a black feather to be evenly distributed and those in a blue feather to be clumped. These two conditions have been found, as might be expected if checks are a combination of black and blue, existing side by side in the feathers of checked birds. It is this difference in pigment arrangement that produces the two different optical effects.
We now know there are no such things as clumped pigments. But first let’s talk about the parts of a feather. The main shaft of a feather is called the rachis. This is the quill that sticks out of the skin. The fine rod shaped structures that come out of the rachis at more or less a 45 degree angle are called barbs or barb shafts. There is stuff coming out of the barb on both sides at about 45 degrees. These tapered rod shaped structures are called barbules. Out on the sides of the barbules are the hook like things that hold the feather structure together called barbicles.
According to Dr. Richard Cryberg, there is a distinct size difference for the pigment granules in smooth spread areas and coarse spread areas. Smooth spread has granules too small to resolve in an optical microscope while coarse spread granules are easy to resolve. Ordinarily in pigeons the bar area of the tail and the ends of the primary flights are smooth spread and the rest of the birds pigment is all larger granules. The large granule area includes both the bar and non bar areas of the wing as well as the non bar area on the tail. Genes like dirty and smoky do not change this relationship. Two genes that have a major impact on the whole bird are dilute and spread. Both of these genes make the granules very small compared to the normal size granules for that area. In the case of spread the granules are likely as small all over the bird as they are normally only in the tail bar and primary ends. Dilute gives less extreme reduction in sizes such that the granules can still be resolved with an optical microscope. According to Cryberg, when we look at a single barb with its attached barbules what we would see is nearly all the pigment is in the barb shaft itself. This pigment in the barb shaft is uniformly distributed. Only a tiny bit gets out into the barbules. This tiny bit in the barbules is what Cole called clumped pigment. However, in reality they are not clumped at all. Each pigment granule is separated from other granules by several wavelengths of light distance. So, the pigment is not clumped; it is simply deposited in islands surrounded by non pigmented areas.
Finally, the least dominant allele in the pattern series, even recessive to the wild-type (bar pattern) is the barless pattern ( gene symbol lower case c indicating it’s recessiveness to wild-type ). Barless in the blue series looks like the wild-type phenotype, but it lacks the bars where the wing shield is clear and has no markings. Barless mutation, which used to be a fairly rare mutation in most domestic pigeon breeds, is now very common in many breeds. As the name implies, the wings lack any bars, which makes the distinction between this type and bar very easy. In a barless individual, the so-called blue colored feathers have entirely replaced the black wing bars leaving a clear blue wing, except for the darkened tips of the primaries, secondaries and tertiaries. Barless is an autosomal recessive trait that is symbolized as ( c // c ), which can be the only condition (homozygous state) for pigeons to show barless pattern in their phenotypes. Therefore, a pair of barless can produce nothing but barless offspring.
Although barless gene most of the times acts like a simple recessive trait, both Graefe and Quinn reported that for some reason barless gene does not segregate out like an ordinary recessive gene. It seems we have three curious cases with the barless mutants: First, from the Hollander’s report on pattern, we don’t know why wild-type birds heterozygous barless crosses ( + // c X + // c ) produce less than expected 1 in 4 ratio, but checks that are heterozygous for barless produce the expected 1 in 4 ratio. Second, in some cases wild-type heterozygous for barless show narrowness of the wing bars but in some cases it doesn’t. Lastly, there seems to be a strange relationship between foggy vision and barless pattern but this curious case only shows up in some barless birds. We probably won’t get real good answers to these questions from the breeding results, and will have to wait until the pigeon DNA is sequenced. Click here to read more about the barless pattern.
When we look at the pattern, it is to be noted that color appears in the rump and in the outer vanes of the outer tail feathers (albescent strip) are inherited independently of the pattern series. It should also be noted that even though each pattern darkens or lightens the feather colors, the effect of pattern series is more distinctive on the wing shields. The patterns differ from each other only in the amount and position of coarse spreading. The barless pattern lacks it almost entirely; the other patterns show in serial array increasing invasion in the wings, the crop, and finally nearly all the body feathers anterior to the tail.
According to Sarah van Hoosen Jones (1921), “ sooty ” has often been lumped with checker, but it is not allelic to pattern series. The sooty can be misleading if it is present with the checker pattern and can make the bird look like a T-pattern Check, make the T-pattern Check look like Spread, and make the Barred birds appear as a Check. Despite a perfectly graduated series of patterns, sharp segregations occur frequently and in pattern series dominance is parallel to the amount of “spreading” involved in the wing shield. In 1938, W. F. Hollander reported pattern inheritance of Columba livia as part of his PhD thesis at the University of Wisconsin. According to Hollander’s study, pigeons have at least six alleles in the pattern series which are Barless ( c ), wild-type ( C + ), Light Checker ( C L ). Checker ( C ), Dark Checker ( C D ). and T-pattern Checker ( C T ). Bar pattern is our wild-type in this multiple allelic series and barlessness is the only recessive allele to the wild-type.
The gene symbols in order of decreasing dominance are C T > C D > C > C L > C + > c
The highest order of dominance can hide anything below it, but nothing above it. This means that two barred (wild-type) parents cannot produce a T-pattern check, or check offspring. There are 6 different alleles for the pattern and each gender carries 2 alleles for any of the patterns that are shown above. The pattern therefore is not sex-linked because every pigeon, male or female carry two alleles for pattern. This makes both sexes homozygous or heterozygous for any of the multiple allelic pattern series. A hen can be heterozygous bar carrying barless or homozygous T-pattern checker (both alleles for pattern is T-pattern checker). But she cannot be heterozygous bar carrying checker, because dominant pattern will always show in the phenotype, and will not be hidden! Unless, of course other mutations are present like spread, recessive red, recessive white, and albino which are all epistatic to pattern series. During mating, each gender donates one of the alleles for the pattern that they carry and the offspring will then show the dominant pattern it receives from both of its parents. If the offspring receives same allele patterns (both bar, or both checker, etc.) then the pattern would be homozygous, otherwise it will be heterozygous at the c locus.
So, recapping quickly. The pattern is located in different locus, known as the c locus (locus is different forms of a gene at a particular physical location on a chromosome) and therefore inherited independently of feather colors. The pattern does not occur only on blue series but in every other mutants except color modifiers like recessive red, spread, and recessive white because these mutations are epistatic to pattern. Understanding the pattern and their inheritance is very important to breeders interested in color, specially to the breeders of Toy Stencils, Oriental Frills, etc.
Let’s apply Mendelian genetics from breeding data to illustrate the inheritance of pattern in pigeons. Let’s assume that members of P1 generation are all homozygous in the following breeding example. We know that pigeons exhibit a checkered or bar (wild-type) pattern as part of the pattern series, and the loci responsible for pattern is located in an autosomal chromosome. Therefore, each gender of pigeons carries two alleles for the pattern gene. In a series of controlled mating, the following data were obtained:
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