Victorian Zebra Finch
Understanding Grizzles and correctly identifying the Pieds
COCK- To conform to the appropriate Colour, but appearing to show White Flecking on all feathers, thus creating a " Salt & Pepper " effect ie; Grizzle. - Cheek Lobes to be Body Colour with approximately 12% Cheek Lobe Colour shown near Tear Drop.
HEN - As for Cock, except all Cock Markings replaced by Body Colour - Hens to show Cheek Lobes of a Lighter Body Colour.
The Grizzle mutation in Zebra Finches is both one of the most difficult to breed to Standard and also one of the most difficult to classify in Judging. Many good Grizzles are rejected as Pieds and many Grizzle Pieds sneak through in the Grizzle class. I believe it is about time that a new approach is used to deal with this mutation at Federation level and that science and logic should be applied to the problem, along with some simple common sense.
There are a few critical features of the Grizzle mutation that need to be understood when evaluating both the Standard and the individual bird. First and foremost is the fact that it is a progressive mutation by nature. The plumage pattern while not being fixed actually increases with every moult throughout the life of the bird. Secondly, it must be realised that the inheritance is more complex than just a single gene Recessive trait. The mutation has at least two pairs of genes involved in its expression and they exhibit cumulative effect. This means the more genes, the more grizzle pattern.
The progressive nature of the mutation means that a bird’s exhibition life is limited under the current interpretation of the standard. Birds that fledge with an ideal Grizzle pattern will be classed as Grizzle Pied by the time they are twelve months old. And birds with light grizzling actually improve with age, sometimes approaching an ideal pattern when four or five years old. Many moderate level Grizzles show no markings upon fledging and moult in the Grizzle markings with the adult moult or even the second moult. Even splits will generally end up showing a small number of Grizzle feathers on the head after three or four years.
The Pied mutation, on the other hand, has a fixed pattern from the time it feathers up. So if a youngster fledges with apparent Pied markings, then without doubt it is carrying the Pied gene. Also without doubt, this is the most reliable time (and possibly the only time) to correctly identify if a Grizzle is Pied or not.
I subjectively divide Grizzle birds into a number of categories that roughly relate to their genetic makeup, but is also dependant upon knowing the exact age of the bird and whether it had pied markings at fledging.
Category 1: a one gene or ‘split’ Grizzle – shows no grizzle markings but may moult a small number into head and neck area after a few years.
Category 2: a two gene Grizzle – shows a small to moderate level of grizzling at fledging or from the first adult moult. Never show apparent pied markings although extent of grizzling improves and extends with age.
Category 3: a three or four gene Grizzle – shows heavy grizzling from fledging will have apparent ‘pied’ areas by one to two years of age.
Category 4: Grizzle Pied – show Pied markings from fledging no matter how many Grizzle genes present may enhance the degree of grizzling through gene interaction.
If we consider that the Federation standard calls for a ‘Salt & Pepper’ effect over the whole body, we find that category 2 birds do not reach close to this until late in life and category 3 birds are misidentified after the first 12mths. Category 4 birds should never be accepted into the class, but confusion is created by the changing nature of category 3 birds and because lower category Grizzles may carry more flecking when Pied is present. Therefore the tendency is to accept birds with small degrees of Pied influence.
At this point, it is prudent to consider the feathering of the bird. The ‘salt & pepper’ effect on the head of the Grizzle Zebra Finch is created by the part coloured/part white feature of each feather combined with the small size of head and body feathers. It is fair to say that flight and tail feathers are at least 20 times the size of the head feathers. Therefore any grizzle markings will also be 20 times as large. Therefore it becomes extremely difficult to produce a fine pattern on the wings and tail due to the size of the feathers and more importantly, it is very easy for grizzle areas to appear pure white and be mis-interpreted as Pied markings in these regions.
Extrapolating the other way, the head area should never have large white markings because of the small, fine nature of the feathers and in fact, this is what we see. But I can already hear you asking “what about ‘Capped’ Grizzles?” They are merely a form of Grizzle Pied, except occasionally in a category 3 bird in old age. Every ‘Capped’ Grizzle I have ever bred had the cap as a fixed feature upon fledging, without doubt a Pied feature by its very nature.
Another observation that should be made of Grizzles is that the markings are not even on each feather. Feathers individually can vary from full colour, through small white tips, onto fifty/fifty colouring and finishing with almost full white feathers with a coloured tip. The heavier markings are more evident in category 3 birds. Pied birds have either full coloured or full white feathers, never partly coloured individual feathers.
So how do we eliminate the Pied birds from the Grizzle class without unfairly penalising the better Grizzle birds? The solution could be relatively simple, if we look for an answer in the Canary world. Not because they have a Grizzle, but by borrowing from something they do to overcome another classification problem – that of defining degrees of variegation into light, medium and heavy so that different judges do not classify in different directions. They achieve this by issuing certificates to the breeder that officially classifies the bird.
For our purposes, what would be required would be for the Judges Panel of each member body of the Federation to examine and issue certificates to Grizzle Zebras within a short period of fledging. These certificates would then define and classify the bird for the rest of its life irrespective of any apparent Pied feathers in later years. If pied markings are present to begin, the bird is recorded as a Grizzle Pied. Each certificate would record the individual birds ring number and the process would only take a few minutes of time if birds were simply brought along to regular club meetings.
Of course, to do this would require agreement on Classification features at a Federation level, something that is only progressing very slowly at present. And it would need to be phased in over a few years because only young birds could be issued with certificates. However it may be the only logical and effective way to deal with the problem. Otherwise we will continue to see good Grizzles being wrong classed because of one apparently white flight feather whilst other birds are accepted with literally hundreds of pure white feathers on their heads.
It will be interesting to see how many Grizzle Pieds are exhibited at this year's Federation show.
By Terry Martin BVSc