Colour Mutations in Aviary Birds - A guide for Bengalese Mutations?

Colour Mutations in Aviary Birds 

The following letter was submitted to the Parrot Colour Mutations and Genetics yahoo discussion group (now closed) called Genetics-Psittacine by a European member. There appears to be a great deal of knowledge and experience across the world when it comes to the science of colour mutations. It seems that the bulk of this knowledge resides within the Hookbill community. This stands to reason I guess, but it is clear that there is much less specific information out there in regards to finch mutations. All that being said, many of the principals directly cross over between Parrots and Finches, but the truth of the type and genetic make up of a particular Mutation in Finches must be assessed individually on a case by case basis. It is quite clear that there are international standards for naming particular colour mutations based on their properties of Phenotype (appearance) and their inheritance.

The letter is around a decade old and after my inquiries with Dr Terry Martin (Group Moderator), I was told that it’s contents are a bit dated in its statements. However this is speaking on a very technical level and I believe that it is a great place to start digesting some information on this topic and then begin to apply it to our limited understanding of Bengalese Finch Mutations.

With Bengalese (as with other finches) there are is great variation in the names of colour mutations between different countries and even different regions of countries. These names are sometimes based in international conventions for naming colours and sometimes the name has more to do with who coined the term for the colour where it was developed.

The Bengalese Finch is a White based bird that only has two types of colour pigments called Melanins, which are essentially earthy colours like red- browns (Phaeomelanin), greys and blacks (Eumelanin). Yellow based Finches like the Red Faced Parrot Finch (RFPF) can display a Green colour when coupled with a Blue colouring of feather. You can see quite obviously with the Pied RFPF that the base colour is yellow.

So when reading through this, bear in mind the relevance that Phaeomelanin and Eumelanin has to Bengalese Finch Mutations. I will add some commentary here and there [PK], that while based in a great deal of research, is to be taken purely as my “opinion” and not necessarily a rule. However this certainly helps to generate our discussions and that what its all about :-)

Aussie Bengos

-Letter-

Hello Terry:

I am really surprised that the English speaking part of the world seems to be completely unaware of things going on in non-English speaking countries. When downloading all digests it struck me e.g. that about a year ago AFA wanted to redo a job that has been done for decades already. I translated below article from Dutch for the U.K. Parrot Soc., where it was published in the December 1996 issue. It was originally published in the monthly of the largest Dutch national Society N.B.v.V. Since it is rather long I leave it to your discretion whether or not you want to put it on the list. It is rather amusing to hear people commenting on the socalled "European names" when most probably they never read this. Worse is of course that , being unfamiliar with the basics of feather structure these very same people do not recognise it's importance and then start re-inventing new colour names for existing ones. The colour names as suggested by the N.B.v.V. are placed between ((...)) and now are in use in both Holland and Belgium.

UNIFORM NAMES OF COLOUR MUTANTS FOR EXOTIC AND PARROTLIKE SPECIES.

Before a name is given to a certain colour mutation it seems sensible to consider the colouring agents in the feathers first. Names based on tradition or for commercial reasons hardly ever are descriptive. The Dutch N.B.v.V. (Nederlandse Bond van Vogelliefhebbers, probably the world wide largest National Society with some 46.000 members) initiated research on feather structure in the early seventies. Based on this the society arrived at a set of names that can be used for both exotic and parrotlike birds. Afterwards standards of excellence forlovebirds, neophema's, psephotus etcetera were written, but also the ones for zebra finches, Gouldian finches or Bengalese made extensive use of these names. Those standards being scientifically based it was in the mid-seventies possible already to predict that for instance dark factors might appear in lovebirds. The major Belgian and French Societies also have accepted a greater part of these names seeing the logic behind them. Below you will find the translation of one of the first articles pub- lished in the N.B.v.V. monthly "Onze Vogels" ("Our Birds") about this subject.

In the feathers of most exotic and parrotlike birds the following pigments MAY be found:

i) melanin, which can be subdivided into:

-Eumelanin (black or dark brown) 

-Phaeomelanin (reddish brown)

[PK] The Chocolate Bengalese or Wild Type Bengalese, has a combination of both of these pigments within its feather structure.

ii) carotenoid, which can be subdivided into: 

-yellow carotenoid

-red carotenoid

In parrotlike birds the name psittacin is used to cover all colours from yellow to red since these pigments most probably can not be influenced by the food given to the animals (as real carotenoids can). Next to above cited pigments the visible colour of the bird can be influenced by the internal structure of the barbs of the feather, the socalled blue structure in a normal (wild coloured) bird.

The black or dark brown Eumelanin [PK] Not present in the Ginger Bengo

The feathers of most birds contain melanin. This presence shows itself as a black, grey, dark or light brown general body colour. When black melanin is found on a white or light yellow base, the body colour will - depending on the concentration of the melanin - vary from (light) grey - (zebra finch, cockatiel) to black (male of the blackbird). When brown melanin is found on he same base colours the colour will vary from light brown to dark brown (Bourke's par- akeet).

The reddish brown Phaeomelanin [PK] The base colour of the Ginger Bengalese

In a few birds only phaeomelanin is found (Bengalese, Chinese painted Quail, pyrrhuras, canaries), however usually combined with eumelanin. When a cer- tain location contains (almost) exclusively phaeomelanin this feather field will show a reddish brown colour (cheek of male zebra finch, abdomen male Painted quail). When both phaeo and eumelanin are present the resulting colour will depending on the concentration of each and the mixture of both lean either towards reddish brown or to black or grey. The blue structure. If next to black eumelanin the barbs also posses the blue structure and this occurs on a white base we see a blue colour (the rump of an Agapornis roseicol- lis). When the blue structure is situated on a yellow base we see this colour as green (Gouldian finch, budgerigar, neophema's, lovebirds). The reddish brown phaeomelanin combined with the blue structure shows a purple colour (breast colour of a male Gouldian finch).

[PK] The high level of variation that we see in almost every individual Bengalese Finch is due to various amounts of these two pigments Eumelanin and Phaomelanin in different combinations.

The yellow and red carotenoids or psittacin

Yellow to red psittacin may be present in a pure form and also in a mixed one. Feather fields containing psittacin only therefore can have a colour from pale yellow via orange to bright red. When these feathers also contain melanin the colour will vary from a rusty brown or olive yellow (Agapornis nigrigenis) to blackish brown or green. Should the concentration of melanin be very high it will mask the colour of the underlying psittacin (head of a Masked lovebird).

MUTATIONS.

The following possibilities for mutation of the colouring agents exist:

MELANIN.

i: A quantitative reduction (a decrease in quantity) of both Eumelanin

and Phaeomelanin if both present ((pastel))

In this mutation the aim should be a 50 % reduction of the melanin. Where the body colour of the wild coloured bird is grey (zebra finch, cockatiel) it will become a very clear grey. If the original body colour is black (male blackbird) it will become grey. For this pastel mutation in these grey shades the name silver is often used erroneously. Where the wild colour of a bird species is reddish brown the pastel mutation will cause this to become a pale reddish brown. For a pastel brown the inapt name cream is used sometimes. In birds with an originally green body colour (Gouldian finch, red rumped parakeets, lovebirds) the pastel mutation causes this to become a yellowish green. This colour is often called yellow mistakenly. [PK] I seems here that the term Pastel is a generic term used when a bird is diluted to a degree of around 50%. Possibly our use of the term specifically for Dilute Gingers may require some review. It seems that the terms Pastel and Dilute go hand in hand.

Next to this 50 % reduction a second one is known causing both phaeo- and eumelanin to reduce over 75 % ((suffused)). The suffused mutation is known in the diamond dove - the so-called brilliant; the Peach faced lovebird - the so called Japanese yellow- and the budgerigar. [PK] We see that in a similar way a 75% dilution can be called “Suffused”. So;

50% Dilute - Pastel 75% Dilute - Suffused

ii: A quantative reduction of the eumelanin ((isabel))

In this mutation there exists a heavy quantative reduction of the eumelanin, while the phaeomelanin remains untouched. Isabel phao will be recognised most easily in those birds where the body colour of the wild form is made up of both eu- and phaeomelanin. (zebra finch, Japanese quail). [PK] It is believed that our Ginger Bengalese is in fact an expression of the Isabel Mutation where all the Black Eumelanin is removed leaving the Red Brown Phaeomelanin. Isabel is in widespread use for a number of mutations that selectively reduce Eumelanin but do not alter Phaeomelanin.

iii): A complete reduction of eumelanin ((phaeo c.q. red brown)

In this mutation the eumelanin is completely reduced, while the phaemelanin remains untouched again. The phaeo mutant therefore will be recognisable only in those birds where both eu- and phaeomelanin are present in the feathers. Depending on the concentration of this phaeomelanin the final col- our will become clear cream to reddish brown (Bengalese). [PK] The reason that I have been advised that Isabel is the best allocation of Mutation type rather than “Phaeo” for our Ginger Bengalese is because the term Phaeo is widely used for a combination in Zebra Finches that actually increases this pigment. So it is more associated as a combination colour rather than a specific colour mutation.

iv: A complete reduction of the phaeomelanin ((grey)).

When phaeomelanin is reduced completely, while the eumelanin remains unaltered. The grey mutation will be recognisable only in birds normally possessing eu- and phaeomelanin (Bengalese). Depending on the concentration of eumelanin the body colour will vary between light grey and dark grey. [PK] At this stage we do not have a Grey Mutation established in Australia.

v: A complete reduction of both eu- and phaeomelanin ((ino)).

In this mutation all melanin is reduced completely but the carotenoids or psittacin remain unaltered. The melanin in the eyes is being reduced as well, this mutant has red eyes. When a bird possesses melanin nor carotenoid or psitta- cin a clear red-eyed white bird appears which is called an albino (Albino Masked lovebird). When the bird possesses yellow or red carotenoid or psittacin only (and no melanin) the ino mutation causes a red-eyed yellow bird to appear which is called a lutino. This yellow may be combined with red. (lutino roseicollis, lutino greenfinch, lutino cockatiel). The ino mutations of those spe- cies possessing a small quantity of yellow pigment only usually are called ino's (sea green ino roseicollis). It does not matter whether an ino has yellow carotenoid or psittacin spread over it's complete body or in certain featherfields only.

vi: A complete reduction of both melanin's (if both present) or of one melanin (if both present) or of one melanin( if only one is present) per feather area ((pied)).

In this mutation melanin is reduced in a certain area. The carotenoid or psit- tacin remains unaltered. Pied birds should comply with the following demands:

-the quantity of "piedness" should lie between 40 - 60 % -the pied pattern should be symmetrical

-the pied areas should be even coloured

-feet, claws and bill should show one colour.

By selective breeding it may be possible to create a fixed pattern (banded pied budgerigar) To obtain the maximum of contrast, pied birds at an exhi- bition are only allowed where no quantative melanin reduction has oc- curred. (P.E. no pied pastels). Of the pied mutation a dominant and a re- cessive form are known to exist. When both mutations are bred into one bird it is possible to breed an even coloured yellow or white bird (dark-eyed yel- low or white).

vii: A qualitative reduction (incomplete oxidation) of the eumelanin ((cinnamon or brown)).

The eumelanin in this mutation has not oxidised completely. It is not black but of a brown colour. Birds not possessing the blue structure will get a body colour variable from clear brown to dark brown. Birds possessing the blue structure will get a very light brown suffusion on top of the green feathers. [PK] A good example of a Cinnamon Mutation in Finches is the Fawn Zebra Finch. It simply “browns” the black/grey of the wild type bird leaving all the detail that the Black Eumelanin creates. Greater perspective can be gained when visually comparing Isabel (Black removed) to Fawn Zebra Finches (Black has changed to Brown). Cinnamon is traditionally a Sex-Linked Mutation where Isabel is often Recessive. I am not aware of an example of a Cinnamon Bengalese but this is more likely because it would be fairly difficult to identify and could easily be overlooked.

viii: A further qualitative reduction makes the melanin granules even smaller then those of a cinnamon and turns them into a grayish brown colour. The final result is the ((fallow)) variety.

MUTATIONS CAUSING A CHANGE IN THE INTERNAL STRUCTURE OF THE BARB ((Dark and Violet factor))

x: The dark factor causes the diameter of the spongy zone to diminish. Sky blue will be seen as cobalt, light green as dark green. When two dark fac- tors are present sky blue will turn into mauve and light green into olive green. The violet factor changes the diameter of the vacuoles of the spon- gy zone and causes a slightly different distribution of melanin in the barbs. In stead of blue light waves the violet ones are reflected. The violet structure shows at its best in a blue bird possessing one dark factor and one or two violet factors.

x: A change in the location of melanin at the centre of barbs

possessingthe blue structure. ((grey)).

Due to a changed internal structure of the barb and a different location of the melanin at it's centre the reflection of blue light waves is prevented. Green becomes grey-green and blue becomes (grey budgie, grey-green ringneck).

xi: A relocation of melanin ((Opaline, laced and pearl)).

In the opaline the melanin is relocated so that no black undulation remains visible in the hind neck and the mantle of the bird. The normal basic body colour now appears (opaline budgerigar). In the laced and the pearl mutation melanin is relocated in such a way that the edges of the feathers change in colour (lacewing budgerigar, pearl cockatiel). [PK] We have a Pearl Ben- galese that was developed in Japan but is not in Australia. We see a lacing effect on the bib of some Dilute Gingers and more so as they are progressively more dilute (moving from Pastel to Suffused). Since noticing this I cannot help but see in some of these Gingers and even in full colour birds a darker rim around the shoulder and flight feathers. I believe that this and other Pearling has some potential to be developed for Bengalese in the future as well.

In Conclusion 

As mentioned previously, all of my comments are to help generate discussion. I do not suggest that I wish to start calling a Ginger or Fawn Bengalese an Isabel from now on but it surely is worthwhile understanding the mechanics of our Bengalese Mutations as we progress forward.