The Opaline Factor in Australian Parakeets

Introduction

George Smith is a veterinarian and aviculturalist who is also a prolific writer on his chosen subjects. To this he brings a wealth of experience and a certain forthright quality in which no punches are pulled in dealing with those whose ideas he considers to be mistaken. George is firmly of the belief that the Opaline characteristic occurs widely in Australian parakeets: examples being the Rosa Bourke’s, the Pied Turquoisine, the Pearl Cockatiel, and the ‘Red’ Eastern (Golden Mantled) Rosella — to this list the Opaline Redrump might now be added. A wild taken example of the Red Eastern Rosella so ignited Gould’s enthusiasm that in writing about and describing it he called it Platycerus ignatus, the ‘Fiery’ Parakeet. And it is in discussing this form of the Eastern Rosella in an article in the Parrot Society magazine (May 1986) that George remarks on various facets of the opaline character.

Jim Hayward is a former bird importer and skilled breeder of parrots, who also writes frequently on a wide range of avicultural interests using a natural artistic flair to bring his subjects to life. His Manual of Colour Breeding is probably the most thorough treatment of its subject to have been produced. However Jim is equally firmly of the belief that neither the Rosa Bourke’s, nor any of the other parakeet varieties, is the equivalent of the Opaline Budgerigar. He has argued this point on several occasions and repeats his views in the above mentioned book.

Who is right in this instance?

The Opaline Budgerigar

The Opaline Budgerigar is the original recognised example of the variety and the one against which any pretenders in other species must be measured. A good example is a little gem. The word judged, which might have been used instead of measured, has been avoided since it brings to mind those who, tasked with adjudicating the English type of exhibition budgerigar, have done their very best to spoil the variety.

The mutant alleles which cause the ever increasing range of parrot colour varieties act in different ways upon the three elements of colour which are present in most species. (see article Colour in the Parrots, Part 2 - The Elements of Colour, in these pages.) Many of these alleles act only upon one of the elements of colour. An example is the blue allele which completely prevents the synthesis of psittacin pigments (yellow, orange, and red) and can turn what would normally be a green bird into a blue bird. Similarly, the ino allele substantially eliminates melanin pigments and can turn a normally green bird into a yellow bird.

The action of the opaline allele is more unusual and complex. In the budgerigar it acts on at least two of the elements of colour and, whilst it does affect the quality of colours to some degree, by far its main effect is to change the pattern of distribution of those colours. The changes, briefly summarised below, do not at first appear overly significant:

1. the zebra markings of the head and neck are much reduced, and there are other distinctive changes to the pattern of black melanin markings
   
   
2. the body colour becomes somewhat lighter whilst attaining a slightly brighter hue and spreading over, and displacing yellow ground colour from, the clear areas of the wing coverts and upper body.

However, further examination of the Opaline budgerigar and consideration of how these changes are effected show that the picture is more complex than is at first apparent. Furthermore, it also becomes clear that comparison with ‘Opaline’ varieties in other parakeet species is not as straightforward as might at first be thought.

Those Matters of Detail

A further and more detailed look at the two points outlined above concerning the changes brought about by the opaline allele in the budgerigar are revealing.

• Point 1 - the changes to the pattern of distribution of black (foreground) melanin.
  
  Looking at the bird more carefully we can see that the considerable lightening of the head and neck is brought about by a narrowing of the black striations rather than any change of colour of the melanin pigment. The other distinctive changes mentioned include: the wing coverts, where the individual feathers show a reduction in the size of the black pigmented area and corresponding increase in size of the clear area, particularly in a section often called the ‘thumbprint’; the upper wing coverts, where there is often increased melanisation with some blotchiness or loss of definition; the mantle and upper body, where melanised areas are reduced or even substantially eliminated; the central tail feathers, where melanin pigmentation is reduced on either side of the dark quill; and finally, and of most significance, a roughly triangular clear area seen on the folded wing near the base of the outer flights where they abut the secondaries. (We will return to this latter feature later.)
  
  
• Point 2 - the change in hue of body colour and its presence in the wings and upper body.
  
  The brightness of body colour and its spread into the wings and upper body is largely responsible for this variety’s particular attraction, and brought to the mind of an early admirer the idea of opalescence. Looking carefully at, and blowing gently on, the feathers of the breast we immediately see that the lower section of each feather and its accompanying afterfeather is pure white rather than the light grey seen in most normals. This is also the case at the rump which is the same hue as the rest of the body colour instead of being rather darker as in the normal.
  
  

From each of the two subjects considered above, the pattern of melanin distribution and the spread of body colour, there is one main aspect which I shall develop. It is these two aspects which, I believe, have the most relevance in determining whether we are justified in concluding with confidence that the opaline factor occurs in species other than the budgerigar.

The Pattern of Melanin Distribution

We can now return to that roughly triangular clear (light coloured) area seen on the folded wing of the Opaline Budgerigar. This is an important and significant characteristic which is always seen in straight Opalines, and also in composite Opalines provided sufficient melanin is present in the flights, and can serve as a diagnostic feature in determining whether a Budgerigar of poor quality or unknown pedigree is some form of this variety.

Many Australian parakeets, and the Budgerigar is no exception, display a typical underwing stripe. More often than not this is present in females and immatures but not in adult males. If individual flight feathers are examined a roughly wedge shaped area is seen running diagonally across about two-thirds of the way down the otherwise strongly melanin pigmented feather. It is these clear areas on each individual flight which combine in the outstretched wing to form the underwing stripe. The stripe is not seen from above because of the overlapping secondaries and for the same reason there is no indication of its presence in the folded wing.

The significance of the roughly triangular clear area on the folded wing of the Opaline budgerigar is that it indicates that the diagonal clear area on each feather is larger than in the Normal and that the underwing stripe is correspondingly wider and more prominently displayed. (I suspect there may be similar changes to the undertail coverts leading to a bolder display in the fanned tail.) As mentioned above I consider the triangular wing patch, indicative of a wider than normal underwing stripe, to be a diagnostic feature clearly setting the Opaline budgerigar apart from the normal or any other mutant form. It may have even greater significance.

Every Rosa Bourke’s parakeet I have seen, whether as a live individual or in a photograph, has exhibited exactly the same feature in the wing at rest; a striking similarity. There can be little doubt this is an indication that the underwing stripe of the Rosa Bourke’s has also been widened by the action of the mutant allele it carries. On this evidence alone we might infer that this is an opaline allele.

But there is a problem here in that whilst it is normal for the female wild-type Bourke’s to carry a wingstripe, this is not usually so in the male. So have I by chance only seen female Rosa Bourke’s, or is there something rather strange going on? Is it possible that where the underwing stripe is not already visible it is, nevertheless, a hidden ‘latent’ feature which can be ‘activated’ by the opaline gene? And if this happens in the Bourke’s does it also happen in those varieties of the Cockatiel, Turquoisine, Eastern Rosella, and Redrump, which show opaline-like characteristics? In short, is the triangular wing patch, indicative of a wider than normal wingstripe, present in all these ‘Opaline’ varieties and to be considered a diagnostic feature in these as well as in the Budgerigar?

Opening my copy of Grass Parakeets and their Colour Mutations (ugh), by H P M Zomer, at the section dealing with the Rosa Bourke’s I see that, indeed, both the male and female are shown in the accompanying illustration as having a prominent triangular wing patch. There may really be something in this ‘latent’ wingstripe idea.

Neither George Smith nor Jim Hayward, or anyone else for that matter, has to my knowledge remarked on this aspect of the changes to the markings of the budgerigar and its possible relevance in assessing the ‘Opaline’ forms of other Australian parakeets. However, I do expect to stand corrected on this assertion for I cannot believe that others have not noticed this remarkable similarity.

Redistribution of Body Colour

The redistribution of body colour in the Opaline Budgerigar has some remarkable features and, despite an apparent similarity, the means by which this is achieved differs substantially from the way superficially similar effects are produced in those other forms of Australian parakeets also thought to be ‘Opaline’.

That difference stems from the fact that in the budgerigar it is truly body colour, that is background melanin and the cloudy layer acting as one, which is extended up and over the upper body and into the clear areas of the wings where it is seen as green or blue depending upon the presence or absence of yellow ground colour. The opaline gene has at best a marginal effect upon yellow psittacin, which is largely controlled by alleles at the blue locus.

Conversely, in the other species we are considering it is ground colour, that is psittacin pigment alone, which frequently has extended coverage and perhaps also changes in hue. In large part this is brought about by suppression of foreground melanin in these areas.

I refer to the above process which occurs in the budgerigar as being remarkable and do not believe this to be an overstatement. The opaline gene appears to operate at the colour distribution level, where it seems that the genetic code ‘knows’ that body colour is produced by the combined presence of both the cloudy layer and background melanin and arranges that they be transferred or ‘activated’ in tandem.

This essential difference between the Opaline budgerigar and the forms of the other species is recognised by Jim Hayward and is the basis for his view that these other forms are not opaline. Uncharacteristically, George Smith does not appear to have realised the possible significance of the differences outlined above and does not differentiate between ground and body colour in the article referred to in the opening paragraph of this article.

Conclusions

So where do I stand on this issue?

Before answering that question, I would like to have a brief look at the mutant forms of the species we have mentioned as possible opaline forms and try to determine what major changes the responsible gene has brought about. This will not be easy as I have little first-hand experience of any, except the budgerigar which has already been adequately covered, and have to rely on photographs and the observations of others. If any of you out there can supply further information or wish to comment in any way please don’t hesitate to come forward.

• The Pearl or Lacewing Cockatiel — foreground melanin is partially suppressed so that many feathers over the upper body and wing coverts have a central clear area of varying size giving an overall spangling effect; there is an enhancement or spreading of yellow psittacin ground colour into the clear areas produced by lack of melanin. Normal hens are said to show a minimal or partially formed underwing stripe; photographs of mutants (invariably hens, since adult cocks of this variety revert to near normal appearance) seem to show the triangular patch on the folded wing, presumably indicating the presence of a properly formed and broad underwing stripe.
  
  
• The Red Eastern (Gold Mantled) Rosella — the distribution of foreground melanin on the mantle and upper wing coverts is disturbed and appears somewhat blotchy, whilst virtually disappearing from the tail; most striking is that, leaving aside the wings below the upper coverts, psittacin ground colour is bright red over most of the bird including the tail and rump. In his description of this, the ‘Fiery’ Parakeet, Gould writes of the feather markings forming the underwing stripe that “... it is normally thrown off as the bird reaches maturity, and is never so distinct as in the specimen ...” being described.
  
  
• The Rosa or Rose Bourke’s Parakeet — foreground melanin (brown in this species) is substantially lost around the chest, head, mantle, back, and upper wing coverts; psittacin ground colour is enhanced considerably in taking up and intensifying the pink already present on the belly and displacing the normal pale yellow hues over most of the body. Most, if not all, Rosas’ show the triangular wing patch and a broad underwing stripe.
  
  
• The Opaline or ‘Pied’ Turquoisine Parakeet — background melanin is lost progressively from the tip of the feathers in the throat, neck, mantle, rump, and upper wing covert areas in a manner which is variable but typically considerably more pronounced in the female; yellow psittacin ground colour is revealed but not noticeably changed in hue where background melanin is lost and, most surprisingly, the females sport a red upper wingbar similar to that of the male. Females and at least a proportion of males carry a broad underwing stripe.
  
  
• The Opaline Redrump Parakeet — no information available.
  
  

From the above observations it seems that, although all these varieties have a fairly obvious similarity in appearance which leads us to think they might be genetically related, the way this is achieved in each species can be quite different. I have already pointed out that the Opaline budgerigar is unique in the way its body colour, rather than ground colour, is redistributed; but it is equally true that there is no overall uniformity in the mechanisms of colour redistribution between the other species either.

However when I look at the Rosa Bourke’s there is no doubt in my mind that, despite the differences brought out above, this must be caused by the same gene as that which produces the Opaline budgerigar. And once this is accepted the other varieties fall into place too.

In particular, in this and other species, melanin suppression around the head, neck, mantle, and wing coverts, together with the frequent exaggeration of the underwing stripe, shows such a strong similarity in all these species as to, in my view, amount to a diagnostic feature.

This gene gives every indication of acting at a deeper level, the colour distribution level, than most other colour genes. And it is as though it ‘knows’ even more than has already been implied; that it has in mind the effect it wishes to produce and uses the mechanisms to achieve this which are appropriate to the particular species in which it finds itself. It also appears, with regard to the underwing stripe, that it is involved to some degree in the mechanisms which differentiate the appearance of the sexes.

What’s this — an anthropomorphic gene?

Copyright: Clive Hesford, December 1998

Terry Martin of Australia responds to this article

Top of Page   •  Other sites index   •  Articles index   •  Books   •  Please take me Home