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.
