by Ken Yorke  (2003)
This group of varieties has caused more debate and confusion due to colour variation in body and
markings than any other budgerigar variety. All of this variation is primarily due to variation in the
quantity of melanin (black pigment) in the feathers of both the body and markings.

Body Colour
The body feathers of a Normal Blue look blue to the eye, however they actually contain microscopic
granules of melanin. This melanin is sometimes called "background melanin" because the black
colouring is not actually seen as black by the naked eye. These melanin granules along with various
other feather structure components result in producing the blue colour your eye sees. The exact same
situation occurs in green birds except they also contain yellow pigment which makes the eye see green
instead of blue. The technical details of how pigment and feather structure cause different colours are
well documented in such classic works as "Genetics For Budgerigar Breeders" by Taylor & Warner
and "The Development Of Color in Budgerigars" by E.W. Brooks.

If the quantity of melanin is reduced the blue colouring loses intensity becoming paler. The more
melanin reduced, the paler the blue colour, becoming white with blue suffusion and eventually pure
white. Likewise green colour becomes paler to yellow with green suffusion and ultimately pure yellow.

Clearwings are generally regarded as having approximately 80-100% of the normal compliment of
melanin. The original traditional Greywing is regarded as having approximately 50% of the normal
melanin quantity. In Australia the Greywing has been deliberately bred in exhibition circles to have a
body colour approaching that of a normal (presumably in the 80-100% area, although I am not aware
of this being accurately measured). The Dilute has approximately 5-10 % melanin with heavily suffused
dilutes likely containing slightly higher levels. From these crude numbers it can be seen how the
variation in the percentage of melanin can either dramatically or subtly change body colour. As with all
living things some natural variation occurs so even a variation of say 10% can be significant,
particularly in Dilutes.

In the markings of a Normal, melanin is seen as black colouring to the naked eye. This is sometimes
called "foreground melanin". Just as in body feathers, the quantity of melanin can be reduced resulting
in colours from black through shades of grey and ultimately white. Greywings are generally regarded as
having approximately 50% of the normal melanin quantity in the markings. Dilutes and Clearwings in
the 5-10% range.

If one incorporates say, 10% natural variation to these numbers, then a clearwing with 20% melanin and
a greywing with 40% melanin now start to look a bit similar in markings. The dividing line between the
two varieties based on visual colouration now starts to get a bit blurry and hence the reason for
confusion in identification. It should be noted that the wing markings on Greywings tend to be more
crisp and well defined than wing markings on Clearwings

Multiple Alleles
An extra complication with Greywings, Clearwings and Dilutes is that they are all genetically related,
being multiple alleles. Multiple alleles is a term that indicates that the same gene has mutated three times
to produce three different varieties. This means that there are six different combinations involving these
three varieties.

Greywing Homozygous Greywing with two Greywing genes
Greywing/Clearwing Heterozygous Greywing with one Greywing gene and one Clearwing gene
Greywing/Dilute Heterozygous Greywing with one Greywing gene and one Dilute gene
Clearwing Homozygous Clearwing with two Clearwing genes
Clearwing/Dilute Heterozygous Clearwing with one Clearwing gene and one Dilute gene
Dilute Homozygous Dilute with two Dilute genes

In some quarters, other alternative genetic theories have claimed the respective existence of two
different Dilute alleles and/or two different Clearwing alleles. Such theories at the present time do not
have widespread agreement.

Traditionally, it has been said that Greywing is dominant over Dilute and partially dominant over
Clearwing. However the reality is not always so clear cut. Greywing/Dilute birds do in fact quite often
have paler body colour, paler markings and paler tails than homozygous Greywings.
Greywing/Clearwing birds generally have a body colour darker than homozygous Greywings and have
been called Full Body Colour Greywings in the past. These heterozygous Greywings which have either
a Clearwing or Dilute gene do not get the full impact of the Greywing gene as does a homozygous
Greywing. In the heterozygous Greywing a blending of features occurs although the overall impact is
still that of a Greywing.

This blending of features is not so obvious in the Clearwing/Dilute heterozygous bird. Some evidence
exists that the Clearwing/Dilute bird has marginally paler body colour, but this is not conclusive, as
other influences, mentioned below, also affect body colour.
Homozygous Greywing Light Green (rear) and a heterozygous Greywing Light Green/Dilute (front).

Note the difference in body colour despite both being Light Green.
Homozygous Opaline Greywing Light Green (rear) and a heterozygous Opaline Greywing Light Green/Dilute (front). These birds are father and daughter.
Note the difference in body colour despite both being Light Green and also the darker markings on the father.
Recent genetic theory has also thrown up the possibility that gene crossovers on chromosomes may
possibly occur within a gene rather than at the logical boundary of a gene. Without going into the
intricate details, if a heterozygous bird had such a crossover occur then the offspring could
theoretically have for instance, one and a half greywing genes and half a clearwing gene. If such a bird
was viable, it could open up a whole new set of possibilties both genetically and visually. There is no
evidence that this has occurred yet, so I will not factor this into this article, but the point is merely
raised for future thought.

From the above, we have the combination of natural variation plus heterozygous versus homozygous
birds which all cause colour variation.

Modifier Genes
Natural variation can be caused by minor influences during early embryo and chick development or
can be driven genetically by modifier genes. Modifier genes work like any other variety gene except
that their influence usually only causes subtle changes which either go unnoticed or are considered not
worthy of giving unique new variety names. It appears that there are modifier genes which can also
influence the quantity of melanin. In fact there appears to be two, if not more, modifier genes whose
effect is most obviously seen in Dilutes and Clearwings and too a lesser extent in Greywings. One
modifier gene appears to effect melanin in body feathers and the other effects wing markings. They
appear to work independently.

In Greywings, Clearwings and Dilutes, these modifier combinations result in birds with light body
colour (in Dilutes it reduces suffusion), or light wing markings. Depending on the variety these
modifiers can be helpful or a hindrance. For instance, light body colour in Dilutes is desirable whereas
in Clearwings and Greywings it is undesirable. Similarly, light markings are desirable on Dilutes and
Clearwings but undesirable in Greywings. Once identified and controlled these modifiers can be useful
to improve the respective exhibition colour features. It is also possible that a modifier exists that
darkens wing markings but it is more likely that slightly darker markings (at least in Dilutes and
Clearwings) is closer to the original mutations but modern exhibition standards have pushed the
varieties toward paler markings as desirable.

There is definitely one particular modifier which is known to interact with Dilutes, Clearwings and
Greywings which makes the markings so dark (bordering on black in the best cases) that it has been
named the Darkwing gene.

The action of modifier genes in the Dilutes, Clearwings and Greywings is so significant, that there are
even alternative genetic theories put forward by some that perhaps only one mutant variety exists (the
Dilute) and all others (Greywing and Clearwing) are merely the result of modifiers and not multiple
alleles. This theory at the present time does not have widespread agreement.

Summarizing so far, we have natural variation, heterozygous versus homozygous variation and
modifier genes which all cause colour variation.

Australian Dominant Grey
An additional issue involving Dilutes, Clearwings and particularly Greywings is the interaction with the
Australian Dominant Grey. Grey (and Grey Green) colouration is also caused by altered melanin and
feather structure. The reduction in the quantity of melanin caused by Greywing, Clearwing or Dilute
has a greater affect on Grey and Grey Green birds often resulting in quite pastel grey and yellowish
grey green body colours, particularly in Greywings.

Yet another influence is Cinnamon on these varieties. The Cinnamon factor essentially turns melanin
into brown instead of black and changes the shape of the granules. The result is a slight dilution in
colour and brown pigment instead of black. The quantity of this brown pigment is just as susceptible
to Greywing, Clearwing and Dilute reductions as if the pigment had been black.

The effect of Cinnamon on Dilutes has been well documented, in fact, E.W. Brooks devotes an entire
chapter to it in his book. In short, Cinnamon causes a reduction in body suffusion and paler markings
and also makes the skin paler (most readily seen in adult birds as pinkish feet). It should be
remembered that melanin exists in skin as well as feathers. Cinnamon makes the cheek patch much
paler from light violet to white. Cinnamon has been used in Dilutes for so long and so commonly that
in Australia up until the 1990's (when English imports arrived) almost every Dilute in that country was a
Cinnamon Dilute. Now that the original non-Cinnamon Dilute bird (which traditionally has more
suffusion) is appearing more often in Australia, they are frequently being seen as a different or new
mutation, but this is unlikely to be the case, merely the re-emergence of the original variety. These
"new" Dilutes from imported stock are visually identical to those true Dilutes which had been kept pure
in small numbers by dedicated Australian colour breeders for years previous.
Cinnamon Dilute Light Geen (left) and Dilute Light Green (right). The left bird is the type exhibited in Australia as a Blackeyed Yellow.
Note the difference in body colour, markings and cheek patch. The left bird, in addition to being Cinnamon also likely has modifiers for reduced suffusion and reduced markings. The right bird probably also has a modifier for reduced suffusion as many dilutes have much more suffusion than even thi s bird.
Cinnamon Dilute Sky Blue (extreme left), Dilute Sky Blue (center left) Cinnamon Dilute Cobalt (centre right) and Cinnamon Dilute Grey (extreme right).
The extreme left bird is the only one which has the suffusion reduction modifiers. The two right birds despite being cinnamon still show suffusion because they lack the modifiers and also the Dark factor helps to make the cobalt show more bluish colour. Note also that the cobalt has the wing marking reduction modifier.
Cinnamon superimposed on Clearwing is also a controversial issue in the exhibition arena. The wing markings of Cinnamon Clearwings are usually so clear that they are barely visible, approaching that of Pieds or Inos. The tail feathers are also considerably clearer. As most standards desire wings with very pale markings then introduction of Cinnamon on the face of it helps this. The down side is that it also causes a reduction in body colour and thus loses a desirable feature of Clearwings, that being the contrast between and wing and body. The controversial issue also arises because Cinnamon Clearwings usually contravene exhibition rules in Clearwing classes. Interestingly, a double standard exists because Cinnamon Dilutes also contravene Dilute classes as well, but they seem to be tolerated, perhaps because judges and officials are unable or not willing to adjudicate on such things.

Cinnamon superimposed on Greywing has no advantages at all, resulting in Greywings with marginally paler body colour, paler wing markings with a distinct grey brown colouration.
Mauve clearwing
Cinnamon Mauve Clearwing.
Note the pale cheek patch, pale body colour and reduced markings.
Cinnamon Light Green (rear), Cinnamon Greywing Light Green (left) and Greywing Dark Green (right).
Note the difference in markings on the Cinnamon Greywing compared to the other birds.
Spangle has negligible influence on body colour of Dilute, Clearwing or Greywing but does affect markings. Spangle of course, produces the typical Spangle edge marking and clear tail. In Dilutes and Clearwings, Spangle gives the impression of less markings. Again these combinations have issues of contravention of exhibition rules.

It can thus be seen that there are many influences on the colouration of Dilutes, Greywings and Clearwings and that it is understandable why from a visual standpoint it can be difficult to differentiate between them. The term "Full Body Colour Greywing" can no longer be reserved solely for the Greywing/Clearwing heterozygous bird as there are now other ways for Greywings to have full body colour. When trying to categorise a bird it is important to think why it might be pale or dark in some feature. Is the bird really as described or is it carrying modifier factors or other varieties such as Cinnamon etc. Some unscrupulous breeders will try to pass off Greywings as Clearwings, or Cinnamon Clearwings as excellent unmarked Normal Clearwings and the innocent buyer then breeds with them and perhaps sells their offspring in good faith resulting in birds of all variations which are not what they are claimed to be. When buying birds of these varieties it is even more important to see pedigrees and particularly see the parents and siblings in the flesh. This helps to eliminate the situation where you are supposedly buying a Greywing but the parents are obviously Clearwings (a genetic impossibility).

Exhibition Standards also need to be reviewed to perhaps decide the direction of the variety features. Should standards reflect the description of a variety as it originally mutated or be coaxed in certain directions by popular fads? Should standards allow only pure mutations or allow combinations of varieties which in many cases produce artificial results not truly indicative of the original component varieties? These may be philosophical issues but such matters do impact on the future of the hobby and indeed the long term viability of certain varieties. In Clearwings and Dilutes, there has already been a move by breeders to deliberately selectively "manufacture" look-alike birds from various combinations of varieties in order to better meet an exhibition standard of Clearwing and Dilute than what the original true mutations are capable of achieving.

* * * * * * * * * * * * * * * *
Addendum (2013)
Homozygous (left) and heterozygous (right) Light Green Clearwings
In the above photo notice the slightly paler chest (particularly around the crop area) on the
heterozygous (i.e. split for Dilute) bird. In this case the paleness is more likely to be caused by the
body suffusion reducing modifier gene than the actual Dilute gene. Amongst the ancestors of this
particular bird were exhibition quality Dilutes carrying the body suffusion reducing modifier so prized
in creating Dilutes with no green suffusion.

In addition to the modifier genes affecting the intensity of body suffusion and markings (mentioned
above in the 2003 version of this article), recent genetic research has shown that other genetic
mechanisms potentially involving tandem repeat DNA and junk DNA can affect the expression of
genes. These mechanisms are undoubtedly partly or wholly responsible for what the layman calls
"natural variation". While this is unproven in budgerigars it is nevertheless highly likely and adds
further complication and variation to the Greywing, Clearwing and Dilute genotype and phenotype

The number of multiple alleles is also a subject of debate. The 1936 Australian Standard catered for
Dilute, Clearwing, Light Greywing (with 50% body colour) and Austral Greywing (with Normal body
colour). Later Australian standards erased the Light Greywing form and retained the Austral Greywing
form (although dropped the "Austral" prefix from the name). Standards in other countries only ever
recognised the Light Greywing form (and did not use the "Light" prefix). It is still not clear to this day
if these original FOUR exhibition categories were to recognise:-
i)  Four different multiple alleles, OR
ii)  Three multiple alleles (i.e. Light Greywing, Dilute, Clearwing) and the Greywing/Clearwing
composite to darken the body (called Austral Greywing or Full Body Colour Greywing), OR
iii)  Three multiple alleles (i.e. Light Greywing, Dilute, Clearwing) and Light Greywing subject to
modifier genes to darken the body (called Austral Greywing), OR
iv)  Three multiple alleles (i.e. Light Greywing, Dilute, Austral Greywing) and Austral Greywing
subject to modifier genes to lighten the wings (called Clearwing), OR
v)  Two multiple alleles (i.e. Light Greywing and Dilute) and Light Greywing subject to modifiers to
darken the body (called Austral Greywing) and Light Greywing subject to modifiers to darken the
body and lighten the wing (called Clearwing), OR
vi)  Some other undetermined genetic categories involving various multiple alleles and/or
combinations of modifiers.

The modern darker bodied Greywing in Australia certainly does not routinely produce any Clearwing
offspring. The modern Clearwing does however occasionally produce small numbers of offspring
which somewhat resemble darker bodied Greywings.
This article and even more information and more photographs appears in the BUDGERIGAR VARIETY BIBLE.