The Genetics of Colour in the Budgerigar and other Parrots
This page updated 16th August 2001
The Par-ino Varieties
[With additional notes on Lacewings and the cinnamon locus]
Sex-linked alternative alleles
Par-ino, or partial ino, varieties have been identified in a number of parrot species. One of the most well known and distinctive is the Clearbody budgerigar. These varieties are distinguished by the fact that the par-ino allele is an alternative allele to the ino, and its corresponding wild-type, and acts at the sex-linked ino locus.
Using the Clearbody budgerigar (see article The Texas Clearbody budgerigar) as an example, there are three alleles in descending order of dominance which can be carried at the sex-linked ino locus:
You may see this expressed in the following way:
wild-type > clearbody > ino
This is a sex-linked multiple-allelic series. (See article Inheritance patterns - multiple alleles for an explanation of an autosomal multiple-allelic series.)
The ino locus lies on the X-chromosome and can carry just one copy of these three alleles. Since a hen has only one X-chromosome, she will express visually whichever of the three alleles is present at the ino locus. A cock, on the other hand, has two X-chromosomes and is able to carry two of the alleles in any combination. His visual appearance is determined by this combination of two alleles and, where they are different, by their relative dominance.
This fundamental difference between the sexes is shown in the following table where it is seen that there are twice as many genetic types of cocks as there are hens. However, because each allele is fully dominant to those below it in the series, there are only three visual types of cock in the budgerigar. (In most other species, however, the par-ino and ino alleles are codominant and as a consequence there are four visual types of cock.)
Some further points are worth making:
Par-inos across species
The Budgerigar was not the first species in which a Par-ino variety was identified. I believe that distinction belongs with the Peach Faced Lovebird (Agapornis roseicollis) where breeders spoke of a relationship between the Sex-linked Dilute (then commonly known as the Australian Cinnamon) and the Ino. It is reported that an article in a 1987/88 issue of Agapornis World by Alessandro DAngieri of Brazil, analysing the breeding results of himself and others, confirmed suspicions that these two vareties were the result of alternative alleles at the ino locus.
Since that time the existence of Par-inos in a number of other species, the Cockatiel, the Ringneck, the Redrump, and the Splendid (Scarlet Chested) parakeet, has been confirmed. A particularly interesting case is that of the Redrump where two distinct Par-ino alleles have been found to occur.
For very many years after its establishment, at the Keston Bird Farm around 1935, the Yellow Redrump was the only mutant variety of this species available in the United Kingdom. In this free breeding species the Yellow became so commonly bred that it eventually carried no premium in value and a very high proportion of Normal cocks were split for this sex-linked characteristic. Its genetic nature attracted comment, especially in view of the brownish tones of its diluted melanin, but in the absence of other evidence the most that could be said was that it had a Cinnamon-like quality. Recognising that Yellow was a misnomer Jim Hayward urged, without it gaining much common currency, that it should be known as the Sex-linked Dilute.
Eventually the Yellow Redrump found its way back home to Australia, where it is commonly known as the English or UK Cinnamon. Lutino Redrumps had been available in that country for some time and when the two came together a familiar story unfolded. The allele responsible for the Yellow, or English Cinnamon, was found to be an alternative allele at the ino locus; the variety was in fact a Par-ino. [There is also a true Cinnamon Redrump in Australia.] It had taken over 50 years and two trips across the equator before this variety was correctly identified!
That was not the end of the story however for another variety, the Australian Platinum, was also found to bear the same relationship to the Lutino. And common to both these varieties is the fact that the par-ino alleles have a codominant relationship with the ino allele. As explained in a previous section this means that in cocks the homozygous Par-ino form has a different, perceptibly darker, appearance to the heterozygous Par-ino/Ino form. Altogether then, four different phenotypes or shades of colour are produced by par-ino alleles in the cock of the species.
But that is not necessarilly the end of the story, for it is likely that the two par-ino alleles themselves have a codominant relationship which will result in yet another phenotype. Fortunately, at the present time these two Par-inos are kept in two distinct populations; which has presented the opportunity for their genetic nature to be confirmed before this becomes all but impossible due their intermingling and the confusing effects of natural variation.
Besides these confirmed Par-ino varieties, the Nemerovsky strain of Cinnamon Quaker parakeets and the Fallow Green Cheeked Conure seem likely to gain that distinction when suitable breeding results are analysed.
[My thanks to Terry Martin BVSc for providing or confirming much of the above information on Par-ino or possible Par-ino varieties.]
Codominance is the rule
I have already mentioned that while in the budgerigar, although only three visual types (phenotypes) of cock are produced by the three alternative alleles at the ino locus, this is increased to four phenotypes in the other confirmed instances where a single par-ino allele occurs in a species. This results from the fact that the par-ino and ino alleles are codominant in these species, rather than apparently having a simple dominant/recessive relationship as in the budgerigar.
Generically, this is shown in the following table where the symbols used are:
The special case of the Redrump parakeet was mentioned in the preceding section. Here the presence of two par-ino alleles may produce five different shades of Par-ino which, in practice, will probably be impossible to identify genetically (or even phenotypically) with any certainty once they come together in one population.
The general action of the par-ino alleles is to considerably reduce the amount of melanin deposited in the feathers. Typically this occurs in a generalised way and appears to affect both foreground and background melanin more or less equally; although foreground melanin is not a prominent feature in many species and there may be subtleties of expression which have yet to be noticed. Par-inos also show a reduction of melanin, where it is present, in body tissue and this feature can be used to distinguish between par-inos and the diluted varieties.
Certainly in the budgerigar this typical expression is greatly modified and, whilst reduction of background melanin follows the usual pattern, that of foreground melanin results in a reduced area of pigmentation rather than the whole being reduced in intensity. (See further comment section of The Texas Clearbody budgerigar in these pages.)
Another noticeable variation of expression concerns the colour shown by the melanin remaining in the feathers. In some species, as with the budgerigar, the reduced deposits of melanin are seen in shades of grey whilst in others there is a more or less definite tendency towards brown or fawn which has led to incorrect use of the terms cinnamon or even fallow. There are too few Par-ino varieties at present for any pattern to even begin to emerge to account for these different phenotypic effects.
The reasons for these variations might be found in the interaction, possibly slightly different in individual species, between the par-ino allele and the rest of the alleles in the biochemical pathway to which it belongs. More likely perhaps, is that they are due to the particular nature of the mutation which has taken place in each of the par-ino alleles. Only where a par-ino allele has been transferred from one species to another by hybridisation can we be sure that two par-ino alleles are identical.
The term Par-ino is useful to categorise and define the genetic nature of this class of mutation across species. It is not, however, acceptable for use as a varietal name to describe any particular instance of its occurrence within a species. But now that this class of mutation is recognized for what it is, there is a great need to standardize on a popular name to be used across species so that each is instantly recognized as belonging to the same group species-wide. The present situation on a worldwide basis is quite chaotic; and confusing to novice and expert alike.
Two names already in limited use in Australia lend themselves well to fulfilling this role in the two main divisions into which many species are already divided for the purpose of naming: the green series and the blue series. Their use is strongly advocated by Terry Martin and I lend my support to this initiative.
As a further refinement the homozygous (DF) and heterozygous (SF) forms can be distinguished:
The name Lime has an attractive ring to it which should appeal to breeders and, whilst pointing firmly to the green-yellow spectrum, is sufficiently imprecise to adequately describe most green series par-ino forms. No less attractive as a name, Platinum, is not quite so obliging in describing the browner par-ino forms but is unlikely to be improved upon.
As a further refinement it has been proposed to the Genetics-Psittacine Discussion Group by Inte Onsman and the BVA that the term pallid be used to denote the mutant allele responsible for the par-inos. The series of alleles at the ino locus would then be:
Remember that the Clearbody budgerigar is a special case in that its phenotype is not typical and also that the ruling bodies governing the exhibition side are always likely to follow their own agenda as regards naming.
The casual misnaming of colour varieties is a perennial problem throughout aviculture, both within countries and on a worldwide basis, and can only get worse as more and more varieties arise. Attempts have been, and are being, made to address this problem but it is an uphill struggle against ingrained habits and widespread ignorance of the true genetic nature of many varieties.
The Lacewing name is a case in point. This variety, in which the body colour is yellow tinged with green and the markings a light brown, first appeared in the budgerigar amongst stocks of Lutinos in the late 1940s and some argument about its nature was aroused which was not resolved for many years. Eventually Dr Trevor Daniels, following a hunch, carried out breeding experiments in the early 1980s which confirmed to most informed breeders that it was a composite variety combining, in a novel way, the characteristics of the Cinnamon and Ino varieties. Even so, doubts remained until Rainer Erhart in 1983 reported the same Cinnamon-Ino combination amongst his Peach Faced Lovebirds.
It now seemed likely that Cinnamon-Inos (Lacewings) could occur by accidental crossover, or be bred by deliberate intent, in any species in which both Cinnamons and Inos were already present. However there were two problems; few breeders really understood in what circumstances the cinnamon and ino alleles could come together; and another distinct variety, the Par-ino, which had an almost identical appearance was beginning to appear.
The general tendency has been to name as Lacewing any variety having a sex-linked inheritance and showing strong reduction of melanin; with what remains showing as light brown of fawn. Inevitably some of these were in fact Par-inos. Recently it has become apparent from unexpected breeding results that, whilst some strains of Ringneck Lacewings are true to name, others are misidentified Par-inos. A similar situation is likely to exist in the Cockatiel. Sorting out which is which is not straightforward since some of the breeding combinations give apparently similar results.
Where doubt exists about whether a colour form is, or is not, a Cinnamon-Ino (a Lacewing) the easiest way to prove its provenance should be by pairing it to a Cinnamon of the opposite sex. In both cases the appearance of young Cinnamon cocks (split ino) will be the proof of the pudding; showing, in each case, that both parents carry the cinnamon allele.
An added complication is that, just as Cinnamon and Ino can combine to produce Cinnamon-Inos (Lacewings), so also will it be possible for Cinnamon to combine with Par-ino to produce Cinnamon-Parinos with, presumably, a phenotype someway between Cinnamon and Par-ino. Popular names to differentiate these Cinnamon-Parinos from Cinnamon-Inos will need to be coined and achieve wide acceptance once their occurrence and distinct phenotype has been verified.
In the budgerigar Cinnamon Texas Clearbodies, that is Cinnamon Par-inos, have already been produced. Due to the novel phenotype which is expressed in the budgerigar they are easy to identify and cause none of the difficulties that might occur in other species. [A photograph showing a Texas Clearbody Cinnamon Grey hen bred by Brett Doran and Sharon House can be seen on the photos page (Texas Clearbodies) at Down Under Budgies.]
Genetic puzzles such as those referred to above are destined to increase in number as mutant varieties are increasingly traded between countries and continents.
The cinnamon locus
Typical characteristics of the Cinnamon varieties are that (usually) black melanin in the plumage is changed to brown and reduced in intensity, accompanied by a similar reduction of melanin in soft tissue. The effects are most marked in juvenile feather when the eye is red, but stabilises as more melanin is being synthesised at the time of the first moult when the eye darkens to a colour often described as plum. Inheritance is sex-linked.
In the budgerigar foreground and background melanin are equally affected. The markings take on warm brown tones and body colour is reduced by about 40% whilst the overall appearance is one of softness and reduction of contrasts. The phenotype is quite distinct: completely different to the Fallows, where melanin reduction is much more differential and marked and browns are greyish; and the one Brown I have seen, where dilution was much less evident and the markings a very dark though definite brown. In species where foreground melanin is not a strong feature this distinctiveness of phenotype will not be so marked.
Unfortunately at least one noted aviculturlist, proclaimed expert and prolific author, Stan Sindel, sees Cinnamons at every turn and claims to have identified many different types graded by the degree of dilution. Many of these are certainly not Cinnamons, any more than some Olives identified by the same authority are true to name. In fact, this author has ignored virtually all existing work on classifying colour varieties according to their genetic nature and instead has concentrated on groupings based only on visual appearance (phenotype) to produce an idiosyncratic system peculiarly his own. Since his books have a wide circulation, even outside his native Australia, the potential for misinformation is great; particularly for those new to colour breeding.
This is not to say that there may not be quite wide variations in the Cinnamon phenotype between different species. Again, as noted previously in relation to the par-inos, it cannot be stated categorically that the cinnamon allele has mutated in exactly the same way in every species. However there is only one cinnamon locus common across all species, and no instance has yet been established of there being more than one mutant cinnamon allele in any one species. That is, there is no indication at present of a multiple allelic series or alternative alleles at the cinnamon locus.
Another practice which may be encountered is that of classifying birds with brown to fawn melanin dilution on a scale of one to ten (1 - 10) purely for descriptive purposes. Although not all such birds are claimed to be Cinnamons, loose use of the colour term cinnamon rather than brown or fawn may lead to misunderstanding.
A way of partially resolving the conflicts brought about by incorrect use of the term Cinnamon has been proposed by Terry Martin. This would embrace the concept of imperfect albinism, which is relatively unknown in aviculture, but much used by avian biologists and others in describing colour morphs. This is a subgroup within the albinistic group which refers to the degree of melanin production both in the plumage and soft tissue.
Complete albinism is the suppression of virtually all such melanin resulting, where there is no other colouring agent present, in (almost) pure white feathers, pink soft tissue and red eyes; the typical Albinos familiar to all aviculturalists, and Lutinos where psittacin yellow is present.
The imperfect albinism subgroup describes an overall partial loss of melanin in varying degrees, and would thus encompass many of the colour forms incorrectly described as Cinnamons as well as the true Cinnamons.
The proposal is that where the term Cinnamon is encountered in the works of the author referred to, or any folowing his example, the term imperfect albinism should be substituted in its place.
There is a fuller discussion of this means of categorising colour varieties or morphs in an article on the Fallows by Terry Martin in these pages. An example of Sindels flawed system is that Fallows are classed as a form of Cinnamon.
© Clive Hesford: January 2001