The Genetics of Colour in the Budgerigar and other Parrots
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The Texas Clearbody budgerigar

These two extracts are from articles published in the Newsletter of the Rare Variety and Colour BS in 1995 at a time when the Clearbody budgerigar, originally imported and distrubuted amongst a select band of ‘top’ exhibition breeders, was becoming more widely available. Not unsurprisingly, little or no worthwhile information had been published by these sources up to that time.


 
Visual nature

Further comment



The Genetic Nature of the Texas Clearbody

Rare Variety and Colour BS Newsletter, Spring 1995.


At last an article by one of the leading lights has appeared in ‘Cage and Aviary Birds’. Alas, the descriptions were vague and the list of possible pairings incomplete. Worse still, mention of an Ino cock split for Clearbody betrayed a lack of full understanding of the now widely accepted genetic theory involved. Five out of ten for effort!

Fortunately our own later contributors, whether from far distant Australia or a mere hop skip and jump away in Holland, know better – though it's never easy to put these fairly technical ideas over in a way that will help the average fancier.

Perhaps, without going into genetic details and schematics I can make a few points useful to the practical breeder:

  • There is a special relationship between Texas Clearbodies and sex-linked Inos (Lutinos and Albinos) – they are ‘allied’ as Ken Gray would put it.

  • Because of this it is not possible for an Ino to mask or hide a Clearbody as is the case with most other varieties.

  • A hen must be a straightforward visual Normal, visual Clearbody, or visual Ino – no sort of combination is possible, and there can be no hidden or split factor.

  • The situation is more complicated with cock birds. There can be:

    1. Pure Normals

    2. Normals split for either clearbody or ino - but not for both.

    3. Visual Clearbodies which can be either pure double-factor (DF) Clearbody or single-factor (SF) Clearbody split for ino. (*see later comments)

    4. Pure Inos - which cannot be split for, or mask, Clearbody.


Breeding the Texas Clearbody

Four possible ways to handle the breeding of Clearbodies come to mind:

  1. Clearbodies can be paired together freely to increase numbers. Inos could well appear but this would be of little concern at this stage. This course might precede one of the other programs or be used by the hobbyist or colour breeder, though care would have to be taken to avoid excessive inbreeding.

  2. Clearbodies can be paired only to Inos (Lutinos or Albinos). This might be the follow-on choice for the hobbyist or colour breeder; those possessing Lutinos with good ‘hot’ colour hoping to introduce this characteristic to the yellow (green series) Clearbodies to subdue green body colour suffusion; or the breeder of Albinos with no sheen (almost certianly Ino Grey Blues) to produce Grey Clearbodies – which are generally recognised to be more attractive than plain Blues.

    A start can safely be made by pairing either cock or hen Clearbodies to an Ino of the opposite sex. The breeding pattern follows the familiar sex-linked fashion with the important difference that the clearbody replaces the Normal as the dominant type. No Normals will appear. However, particularly depending upon the source of the Inos, various other factors (notably dilute) may be present and eventually come to the surface to produce wastage, Dilute Clearbodies are unlikely to be desirable.

    Hens will be exactly as they appear – pure Clearbodies of Inos.

    Cocks will be either pure Inos or one of two types of Clearbody – pure (DF) Clearbody or SF Clearbody split for ino.

  3. Clearbodies can be crossed only with pure Normals. This would be the method of choice for breeders seeking the shortest route to maximum exhibition ‘quality’. The preferred starting point would be a hen Clearbody (since this is by definition pure) paired to a cock known not to be split ino. If only a Clearbody cock is available, he should be paired to a Normal hen and any Clearbody daughters used as a starting point. If any Ino hens appear, they, their fathers, and their brothers, should be excluded from the program.

    Once established, the breeding pattern is again exactly the same as for any of the popular sex-linked varieties (Opaline, Cinnamon, etc.) and should present no problems for a breeder acquainted with these varieties.

    Hens will be exactly as they appear — pure Normals or pure Clearbodies.

    Cocks will be — Normal, Normal split for clearbody, or double-factor Clearbody.

    Initially, at least, there will be a high wastage rate of lesser-quality Normals; besides any Inos and other undesirables which may appear.

  4. Finally, Clearbodies can be paired to both Normals and Inos. This choice is best made by by the experienced breeder who has an understanding of the genetics involved and clear objectives to pursue.

As usual in any genetic discussion, the description Normal is used in the sense that such a bird does not show or conceal any of the factors being considered; in this case clearbody and ino. Other factors may well be present in practice and be desirable, dark, grey, violet, etc. Others, particularly diluting factors, may also be present and will in general be undesirable.


More questions

American breeders have suggested that Clearbodies produced from pairings with Inos have reduced body colour (green or blue) suffusion.

In the case of hens this could only be due to any differences in genetic background between Normals and Inos and I do not see this as being true as a general and universal rule. Where cocks are concerned there might be more substance in this argument. There could well be differences between doule-factor Clearbody and single-factor Clearbody (split ino) cocks. But, as always, I implore, don't repeat such views unless you are convinced by careful personal observation that they are true. Don't become a myth-monger!

If any of you do breed Clearbodies, I'm sure it would be a great help to the rest of us if you could provide accurate descriptions of straight Clearbodies and the Opaline variant which is so (relatively) commom. In particular, what are the changes to the distribution and colour depth of the markings besides the well-known dilution of the flights? And can you see any difference between double-factor and single-factor cocks?


© Clive Hesford, 1995


 
Back to top Genetic nature Further comment


The Visual Nature of the Texas Clearbody

Rare Variety and Colour BS Newsletter, October 1995.


No-one has yet responded to my invitation to come up with a description of the Texas Clearbody. In view of this, and even though speaking from a prior position of almost total ignorance, there is nothing for it but to take up my own challenge and venture first where others fear to tread. Then you can tell me where I’ve gone wrong!

Back in the days when the Clearbody was just a name, we used to visualise it as having pure yellow or white body colour contrasting with perfectly normal markings. The reality is rather different. Glancing at Clearbodies on the showbenches reveals a wide variation in appearance, made more so by the fact that some carry Opaline in their make-up. This doesn’t make it at all easy to decide on the typical appearance of the variety.

However, at the Specialist and Rare Variety Show (Summer 1995) I spotted a couple of Clearbodies exhibited by one of our members, Mrs Dolores Noonan, which it seemed to me best expressed the basic characteristics of the variety. They, a cock and a hen, stood out from the rest for the richness and contrast of their colour. Whether this was the result of their being more typey and tight-feathered than the others, or to the manner of their breeding, I don’t pretend to know.

I base the following observations on these birds:

  • The effect of the clearbody gene is to reduce melanin production: both foreground melanin (the markings) and background melanin (base for body colour) being affected.

  • There is no change in the yellow ground colour of green-series birds, nor is it likely that the cloudy layer is affected.

  • Body colour (green in green-series, blue in blue-series) is diluted quite strongly as a result of the reduction in background melanin. The dilution is strongest on the breast and less so on the flanks and rump. Consequently, the green-series Clearbody has a generally yellow appearance with green suffusion most evident on the lower body and flanks, whilst the rump is a definite green – perhaps 40-60% of normal. (This pattern of body colour is reminiscent of the Fallows.)

  • It may be assumed that the after-feather (down) and base of the contour feathers are yellow or white – not grey as in most normals.

  • The markings are black, of normal or near normal intensity, and follow the normal pattern of distribution except that:

    1. The flights are very strongly diluted to a pale grey (on a par with those of the dilute) and,

    2. The central parts of the wing covert feathers, medium grey possibly tinged with body colour in normals, are also strongly reduced if not clear. Consequently, the markings in general appear somewhat less pronounced than in a normal, with more ground colour (yellow or white) evident between the shell markings.

  • Tail feathers are of normal appearance (dark blue in green-series) as are the eyes, the cere, the cheek patch, and the spots.

  • The feet and legs show a moderate reduction in pigmentation and tend toward the pink of the Ino. (This may have implications for the eye colour of chicks.)

Most breeders of Clearbodies will probably wish to improve their stock by reducing green or blue suffusion. As with other varieties with largely yellow or white body colouration (Dilutes, Lacewing, Fallow, etc.), a certain amount can be done by selection. But the most immediate results will follow from incorporating certain colour modifying factors in a way which by now should perhaps be common practice.

In the blue-series, the addition of the grey gene will replace the objectional (in some instances) blue suffusion with grey suffusion, whilst also tending to intensify the markings. In the green-series, the dark and violet genes will both help to disguise green suffusion and persuade it to blend in with yellow ground colour. They may also slightly deepen the markings. The opaline gene may help to reduce suffusion of the rump, though at the expense of altering the markings.

It seems to me that the challenge which breeders of the Clearbody will increasingly face is that of preserving the pattern and intensity of the markings. Already, there are signs that the exhibition Clearbody will soon be just as nondescript as most Spangles are today. (see The Nondescript Spangle?)


© Clive Hesford, 1995


 
Back to top Genetic nature Visual nature


Further Comment

The Clearbody Phenotype

A peculiarity of the Clearbody or par-ino budgerigar is the unexpected and novel visual form, or phenotype, which it exhibits. It might have been expected that there would be an even overall reduction in melanin in the plumage resulting in an appearance very similar to that of the Lacewing.

As we all know however, whilst this is what does appear to happen in Par-inos of other species, there is more to it than this in the Clearbody budgerigar. Although the processes initiated by the clearbody allele do indeed reduce melanin production, they do so in a selective manner which produces an altogether more interesting phenotype.

The process is fairly subtle with regard to background melanin, and I have not seen it noted by others, but my description above does bring out the fact that there is a noticeable differential reduction in body colour – which is most reduced on the breast and deepens outwards from this area. But when it comes to foreground melanin it cannot be missed by even the most casual observer that, rather than there being a general reduction in the intensity of the markings, there is instead a reduction in the total area of those markings – resulting in a distinctive pattern possessed by no other variety.

This is most noticeable in the flight feathers which are reduced to a very pale grey – though there is just sufficient pigmentation left to reveal the presence of the characteristic white triangular area when the Opaline trait is also expressed in an Opaline Clearbody.


The budgerigar clearbody allele belongs to that class of mutation known as the partial- or par-ino. This means that it is an alternative allele to the ino, and its corresponding wild-type, and acts at the sex-linked ino locus. This is discussed in more detail in another article:


The Par-ino Varieties


© Clive Hesford January 2001
http://ourworld.compuserve.com/homepages/clivehesford/
e-mail: CliveHesford@compuserve.com

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