Crossbreeding and The Mechanics of Color

The FOB Theory
The FOB theory for Budgerigars was devised by two geneticists--scientists who specialize in heredity based on the theories of the discoverer of genetics, Gregor Mendel. Their names were Dr. Duncker and Dr. Cremer. They distinguished three main colors or critical factors for Budgerigars: The yellow factor, designated by " F ", the blue factor, designated by " O "; and the dark factor, called "B." The corresponding recessive (or "shy") factors were indicated by the small letters "f," "o," and "b."

Later a fourth factor was identified, namely the one for graywings. The graywing factor is recessive for the O factor, but dominant for the o factor. To clarify the differences, one now uses the designation "On" for the plain dominant dark factor; "Ow" for the recessive dark factor, and "Og" for the graywing factor.

By this scheme, a light green, homozygous, purely inheriting Budgerigar gets the F factor from both parents, and is designated as FF. Both parents also contributed the factor On, which makes it On On. And it has the b factor from both parents, making it bb.

The complete designation for light green homozygous (purely inheriting) Budgerigars therefore is: FF On On bb.

After repeated crossings, geneticists determined the following:

Birds designated F are green and yellow

Birds designated On are green or blue

Birds designated ff are mostly bluish

Birds designated Ow Ow are yellow or white

Birds designated bb are light in color

Birds designated Bb are in between light and dark

Birds designated BB are dark

Birds designated Og are graywings.

With this list in hand you can make up a designation for any Budgerigar, indicating both the visible and the invisible (recessive) coloration. The designations for the best known mutations are as follows:

1. Light green FF On On bb       

   Dark green FF On On Bb

   Olive Green FF On On BB

2. Light green/blue Ff On On bb

   Dark green/blue Ff On On Bb

   Olive green/blue Ff On On BB

3. Light green/white Ff On Ow bb

   Dark green/white Ff On Ow Bb

   Olive green/white Ff On Ow BB

4. Graywing light green FF Og Og bb

   Graywing dark green FF Og Og Bb

   Graywing olive green FF Og Og BB

5. Light green/graywing FF On Og bb

   Dark green/graywing FF On Og Bb

   Olive green/graywing FF On Og BB

6. Light green/blue graywing  Ff On Og bb

   Dark green/blue graywing Ff On Og Bb

   Olive green/blue graywing Ff On Og BB

7. Graywing light green/blue Ff Og Og bb

   Graywing dark green/blue Ff Og Og Bb

   Graywing olive green/blue Ff Og Og BB

8. Graywing light green/white Ff Og Ow bb

   Graywing dark green/white Ff Og Ow Bb

   Graywing olive green/white Ff Og Ow BB

9. Skyblue ff On On bb

   Cobalt ff On On Bb

   Mauve ff On On BB

10.Skyblue/white ff On Ow bb

   Cobalt/white ff On Ow Bb

   Mauve/white ff On Ow BB

11.Graywing skyblue ff Og Og bb

   Graywing cobalt ff Og Og Bb

   Graywing mauve ff Og Og BB

12.Skyblue/graywing ff On Og bb

   Cobalt/graywing ff On Og Bb

   Mauve/graywing ff On Og BB

13.Graywing skyblue/white ff Og Ow bb

   Graywing cobalt/white ff Og Ow Bb

   Graywing mauve/white ff Og Ow BB

14.White skyblue ff Ow Ow bb

   White cobalt ff Ow Ow Bb

   White mauve ff Ow Ow BB

15.Light yellow FF Ow Ow bb

   Dark yellow FF Ow Ow Bb

   Olive yellow FF Ow Ow BB

16.Light yellow/white Ff Ow Ow bb

   Dark yellow/white Ff Ow Ow Bb

   Olive yellow/white Ff Ow Ow BB

17.Graywing light yellow/white FF Og Ow bb

   Graywing dark yellow/white FF Og Ow Bb

   Graywing olive yellow/white FF Og Ow BB

Conclusion to Be Drawn:
These lists have a special purpose. Let's have a look at what they tell us. Take, for example, the second item under category 5: Dark green/gray-wing. As I mentioned earlier, this refers to a dark green Budgerigar with a hidden graywing trait. The bird, therefore, looks green and can't be distinguished visually from a plain green Budgie. Speaking professionally, the bird is a dark green with a graywing gene, or dark green split for graywing. The designation is FF On Og Bb.

The list also shows that a bird with F in its designation is green or yellow. A bird with On is green or blue. The Budgie in our example, therefore, has two reasons to be green, namely the F and the On factors. In the designation, we further encounter Og, which identifies it as a graywing according to the list. This is not visible, but the designation clearly indicates that the bird carries graywing blood. The last letters in the designation indicate that the bird is neither light nor dark, which in this case means neither light green nor olive green, but dark green.

Consider another example: Item three under category 13, graywing mauve/white. Technically it is a graywing mauve split for white. This bird therefore has the outward appearance of a mauve Budgie with gray wings, but it carries the hidden trait for white.
Its designation is ff Og Ow BB.

By referring to the list, you can draw the following conclusions: 

The Budgie is ff, thus bluish.

The Budgie is Og, thus a graywing.

The Budgie is Ow (no conclusion possible).

The Budgie is BB, thus dark.
From all this you can see that the designation can tell you the color of the bird.

If you take a random designation, say ff Ow Ow bb, and refer to the list, you can deduce the following:

The Budgie is ff, thus bluish.

The Budgie is Ow Ow, thus yellow or white.

The Budgie is bb, thus light in color.

And the list shows that this bird is white skyblue.

Say that you consider buying a Budgie about which it isn't known whether it is homozygous or heterozygous, but you can see that the bird is light yellow. By referring to the list, you find that the bird could have the following designations: Ff Ow Ow bb or FF Ow Ow bb. In the first case, the Budgie is homozygous--pure light yellow. In the second case, the bird is heterozygous--light yellow split for white.

Visually, the genetic color picture cannot be determined. But if the bird is crossed with another Budgie, you can tell by the young if the bird you're considering is homozygous or heterozygous. One crossing usually can help you determine what the exact designation of the bird is. If you know the proper designation of your stock, then it is easy to predict in advance the result of any crossing. All you need is to write the designation of the birds you want to cross as an arithmetic problem and compare the result to the numbered list.

Now let's look at some examples to show what will happen when two homozygotes--two purely inheriting birds are mated. Take white skyblue white skyblue.

For a simple look at the results, write the designation of the birds at the top and the left hand side of a plain diagram. In the small boxes, on top and to the side, write half of the designation of both birds, since the young inherits half of its chromosomes from its mother and half from its father. Add the "half designations" two by two, put the result in the big boxes, and you will get all possible designations that can result from this crossing.
The diagram looks like this:
White Skyblue ff Ow Ow bb
f Ow b f Ow b
White Skyblue
ff Ow Ow bb
f Ow b ff Ow Ow bb
White Skyblue
ff Ow Ow bb
White Skyblue
White Skyblue
ff Ow Ow bb
f Ow b ff Ow Ow bb
White Skyblue
ff Ow Ow bb
White Skyblue

In the four big boxes (lower right) you keep seeing the same designation of ff Ow Ow bb. That shows you that the young all have the same designation as each other and the same designation as the parents. From this calculation, we can conclude that all birds issuing from this cross will be white skyblue. However, as soon as one of the factors is different, the situation changes. Say that we pair a white skyblue Budgie with a white mauve Budgie.
The resulting diagram would look like this:
White Skyblue ff Ow Ow bb
f Ow b f Ow b
White Mauve
ff Ow Ow BB
f Ow B ff Ow Ow Bb
White Cobalt
ff Ow Ow Bb
White Cobalt
White Mauve
ff Ow Ow BB
f Ow B ff Ow Ow Bb
White Cobalt
ff Ow Ow Bb
White Cobalt

In the four big boxes (lower right) you keep finding the designation ff Ow Ow Bb for the results of this cross. Referring to category 14 in the list, you find that this means white cobalt. The calculation shows us that all the young from the white skyblue white mauve cross will have the coloration of white cobalt.

Another cross, mauve/white olive yellow, yields the following diagram:
Mauve/White ff On Ow BB
f On B f Ow B
Olive Yellow
F Ow B Ff On Ow BB
Olive Green/White
Ff Ow Ow BB
Olive Yellow/White
Olive Yellow
F Ow B Ff On Ow BB
Olive Green/White
Ff Ow Ow BB
Olive Yellow/White

It's easy to see that the young from this cross will be half olive green/white and half olive yellow/white. At the risk of excessive repetition, let me add that all the young are "split for white," meaning heterozygous, or inheriting impurely. They look like homozygous olive green and olive yellow Budgies, but they all carry the white trait. By devising the proper cross, the next generation can be made to exhibit this hidden trait like a rabbit coming out of a hat.

Let's try another example. If we cross mauve/white with graywing cobalt, we get:
Mauve/White ff On Ow BB
f On B f Ow B
Graywing Cobalt
ff Og Og Bb
f Og B ff On Og BB
ff Og Ow BB
Graywing Cobalt
ff Og Og Bb
f Og b ff On Og Bb
Cobalt Graywing
ff Og Ow Bb
Graywing Cobalt/White

The result of this cross, which again is shown in the large boxes, is as follows:
One quarter mauve/graywing, one quarter graywing mauve/white, one quarter cobalt/graywing, and one quarter graywing cobalt/white. Half of these birds will have a trait for graywing, although this trait isn't visible to the eye. The other half has the hidden trait for white. All birds out of this cross, therefore, have a hidden trait for a color different from the one they show; and all these birds, therefore, inherit impurely they all are hetero-zygotes. To the eye, these birds look as follows: One quarter mauve, one quarter cobalt, one quarter graywing mauve and one quarter graywing cobalt. This analysis is credited to the German geneticist Dr. H. Duncker. He continued further by writing a book about color inheritance of Budgerigars.

The Law of Averages:
In analyzing the last table, I spoke of "halves" and "quarters" in predicting the coloration resulting from a certain cross. Don't assume however, that in a brood of eight, precisely two will belong to each of the four designations I listed. Nature doesn't work that way. The outcome follows the law of averages. The designations will come out in the predicted ratio if the number of cases involved is large enough, say 100 birds.

In any one nest, things can be different. It is possible, in the extreme, that you will get only olive green birds in a brood where you expect to find both olive greens and olive yellows. In the next brood, things could work out differently, and you might find more olive yellow birds than you expect. Those who have had a hen brood a clutch of eggs know that you might have the good luck of hatching out mostly females and just a few males. Yet in theory, you know there ought to be equal numbers of hens and roosters. A large scale breeder will tell you that this is true if you use large numbers.

(The sex ratio in Budgies also is about even. The young are theoretically half female and half male. But you still might hatch out a brood with only females or only males.) To become familiar with the mathematics of crossbreeding, make up some theoretical combinations of your own and see what the results would be. Take two types of Budgies at random from the numbered lists and see what they would bring forth.

You are convinced by now, I hope, that you can use this system to predict what you can expect from crossing your own stock. Of course, you need to know what hidden color traits might be tucked away inside the cells of your own. The easiest way to find out is to buy birds whose heritage is known to the seller. All you need to do then is to look up the proper designations and make your diagram. If you can't buy what you need, you will have to determine the correct designation of your birds with one or more test matings. Then you will have to keep careful records on your stock. Accurate bookkeeping is essential for a breeder who wants to know what he is going to be breeding.

Limitless Possibilities:
As soon as you delve into the genetics of Budgerigars, you will come to learn that there are limitless possibilities. One keeps facing surprising discoveries. "Theoretical breeding" is a pleasant sport to occupy your time with. The Budgie breeder can sit by the fireplace on a cold winter day, and relax while pondering the possibilities that his birds present. He can search for the right combinations and then make up the right couples to attain a definite goal during the next breeding season. He can think about the difference between a cobalt/graywing and a graywing cobalt/white. And he can work backwards to find which parent he would have to have for breeding, let's say, a graywing light green. He discovers that olive green/blues only can produce cobalts and mauves. Birds that are green/white, can bring forth blue, yellow, and white Budgies, provided they are mated properly.

Dr. Duncker found more of these good bits of information. A "split for blue" designation doesn't say anything about the type of blue factor the bird has. If you want to be sure about it, then you have to designate the blue factor more precisely with cobalt, etc. In practice, that can be difficult because the proper designation of a visible blue already is quite hard. Another point, which ought to be clear to any breeder, is that there can be a wide difference in the color of two skyblues or two mauves. One skyblue can be a bit darker than another, but not really quite dark enough to be called a cobalt. With other colors, similar situations can arise. A look at any cage with ten light greens will easily convince you of that point.

Practice Versus Theory:
I have discussed the advantage of breeding from one pair of birds per cage. There is no way to know the father of a bird bred in a colony. But I don't want to reject colony breeding since I know that practical limitations often impose themselves on theoretical preferences. But a single colony breeding cage is suitable only for a limited combination of birds. You could, however, breed cobalts or pure olive greens or pure lutinos. If you remove all young with deviant coloration, you will eventually have a pure race from which you can keep selecting the best individuals.

In addition, you could put all birds from the white series together in an aviary for example, light green/white, dark green/white, skyblue/white, etc. You can be certain that every bird hatched in this aviary will be born with a visible or invisible white factor in its makeup. All birds from the blue series can be put together in a cage with yellow Budgies. You can be sure that every bird that looks green carries the factor for white. All the white series with so called blue, mauve and cobalt "haze" can be put together in a single breeding cage. (In reality, there are no white birds.

White Budgies all have a more or less vague ground color, which lies like a haze over the white. Truly pure white Budgies are albinos.) Your calculations will show you which birds can be put together in a cage to achieve the results you desire. If you specialize, say in lutinos, blue whitewings, or light blues, then things will go quite easily for you. All you have to concentrate on is one key element: rigorous selection.

All in all, however, the results of Dr. Duncker's FOB theory of crossbreeding are recognized as correct by all geneticists, including the two just named. After all, the theory has been proven correct time and again in practice. However, if you wish to delve further into the truly exceptionally interesting study of the genetics of the Budgerigar, I gladly recommend these two books to you.

Breeding for a Different Color Variation:
If you want to get into a new color variation, the easiest way, of course, is to buy a couple of birds of that color pure breeding birds, that is, homozygotes. Then you know that all young from the mating will be of the desired color; the pure and simple reason is that the young get this desired color both from their father and from their mother. Unfortunately, this easiest of methods also is the most expensive, particularly if you want to go into something that was just recently developed. You can get the same results with a much smaller cash outlay by buying just one bird of the desired variety. In a few matings, you can build a whole race of the new variant.

Say you have skyblues and you want to build a race of graywings. Go out and buy a single graywing blue--a pure one, of course. Starting with the mating skyblue graywing blue, you will get all skyblue looking young. But you can be sure that every bird out of this crossing is "split for graywing", that is, it carries graywing genes. Next, cross one of these young back to the original graywing, that is graywing blue blue/graywing. That will yield half blue graywings and half "split for graywings." You have reached your goal with just two crosses, in this case!

You could save still more money by buying two "split for graywings," that is, two birds with graywing genes. Start by pairing two skyblue/graywings. The first generation of young would yield 25 percent graywing blues. These birds can be identified immediately as graywings. You even could make do by buying just one "split for graywing," but it will take more time to reach your goal and you'll encounter more difficulties along the way. Start by crossing skyblue skyblue/graywing; there won't be any visible difference between these parents. You will get young that are partially skyblue and partially skyblue/graywing. There also won't be any visible difference between these young. Mate them among themselves and you will eventually achieve a mating between two "split for graywings." Before your own eyes, two Budgies that are blue in appearance "suddenly" will produce graywing young.

This discussion will clarify for you how two green birds (or birds of any other similar appearance) can produce a completely new color. You can get white birds suddenly in a breeding cage where you wouldn't expect any. The explanation is similar. Both parents would be "split for white" in this case, even if this never came to light in earlier matings.

Inbreeding, a word that sounds like a curse to many Budgie breeders, is one we have encountered earlier in this book. French molt, illnesses, and failures of all kinds have been attributed to inbreeding. There really is such a thing as regression of a race through inbreeding.

But the problems that the average breeder attributes to inbreeding mostly have other causes. The chief cause is poor selection. One has to know why and with what one is inbreeding. Scientifically, inbreeding means the mating of two closely related animals. Every Budgie, of course, has two parents, four grandparents, eight great grandparents, and 16, 32, 64, 128, etc. forebears in earlier generations.

After 20 generations the group of forebears numbers well over two million. That would take in most of the Budgies in the country. As a result, if we would stop bringing in fresh blood from abroad, this would mean that every Budgie in the country is related to every other in one way or another. If you pair two birds at random from this "family," however, you can't call it inbreeding, even if you can demonstrate a relation in the so-maniest degree. You can speak of inbreeding only when mating the closest of relatives--parents with young, brothers with sisters, or two cousins together.

Actually, even breeders with a strong dislike for inbreeding resort to this practice at some time. They are striving for a certain goal, and to reach this goal, and to reach it quickly, inbreeding is often the only possible means. I mentioned earlier that you may only have to buy one new bird of a certain color variation in order to establish that variation in your stock. I mentioned that the way to achieve this is to use inbreeding. For example, say you want to breed fallows and have only one fallow bird to work with. You begin by crossing this fallow with a "not fallow." The progeny is 100 percent "split for fallow", birds that carry the fallow as a hidden factor. To get fallows from the next generation, you have to mate the "split for fallows" with their pure fallow parent.

That's inbreeding! The result is 50 percent "split for fallows" and 50 percent pure fallows. Another motive for inbreeding might be that you have a bird of especially beautiful conformation. If you want to keep this conformation in your breeding, you can easily select a mate from the same family. You mate the good bird with one of its own young that exhibits the same superior conformation. The result will be young that maintain this trait. In this way, you can breed a whole race of birds with the trait.

There is a "but" attached to inbreeding, however. Inbreeding transmits not only the good but also the bad traits. As you know, when a sperm cell fertilizes an egg cell, each contributes half of the chromosomes and genes of the parent birds. The new individuals inherit the traits of the male and the female by way of these chromosomes and genes--good ones as well as poor ones. The breeder has to try to maintain and strengthen the favorable traits in the progeny of these birds--and to get rid of the unfavorable ones. With good luck, the male and female have the same good trait, and the young will inherit this trait in augmented form. With bad luck, both parents have a certain unfavorable trait, and the young inherit this bad trait in augmented form.

So you understand why rigorous selection needs to be maintained when you inbreed. Not all inbred young have inherited the good traits of the parents without any of the bad ones. You would preferably breed further with the young that inherited the good traits and not the bad ones. That is called selective inbreeding.

Say for example, that you have opalines that stand out for their attractive design but also have a hollow back. Selective breeding can be your means to try to maintain the design while getting rid of the hollow back. You keep looking for related birds that have the desired design at its most attractive and have the least noticeable hollow back. In theory, this method should make it possible to breed a pure white Budgie--one that is not an albino. Perhaps it is possible to achieve it in reality as well. One would keep selecting the whitest Budgies and inbreed from them. Slowly, you would breed a Budgie without underlying color. Through inbreeding one can achieve great purity within a family and it reduces the likelihood of variations.

Since selection is essential, inbreeding requires the breeder to work with relatively large numbers of birds. It is recommended to breed in so-called parallel series--for example, brother-sister matings. The selection for further inbreeding is increased in this way and the breeder isn't tempted so easily to use birds with bad traits for further breeding. However, inbreeding is not recommended as the only way to achieve the goal of well-formed Budgies of an attractive color. You can use non-related birds to breed a line with desirable traits through intelligent selection.

Outside help from an unrelated bird can often yield results that are at least as favorable. The decision is yours. To make it, you need more than you can learn from a text. You need experience and, even more important, love for your task.

Dominant and Recessive Faults:
I have spoken in depth about dominant ("aggresive') and recessive ("shy") traits--mostly in connection with color selection. The same forces are at work with all inherited traits, including undesirable ones. A good example in Budgies is black spots on the throat. Birds with the dominant gene for these spots will transmit this factor to their young when mated with other birds having this gene. People like the spots, so this is a desirable trait.

But undesirable traits also can he caused by dominant genes. Matings of two birds with the same undesirable dominant genes can make the throat spots disappear from the race, in whole or in part. If you mate a bird with a dominant gene for a certain fault with another that has the gene in its recessive form, then the fault will appear in part of the descendants. You can then use selection to eliminate the fault in future generations. A breeder who values attractive, large, round throat spots has to concentrate on finding birds with the dominant fault and to eliminate them from further breeding. He would make a few trial selections to rather simply detect the undesirable birds. Recessive faults are harder to detect. They may suddenly appear in a race that had been considered pure. These are called throwbacks. No breeder likes them, but if he has a sufficiently large number of birds, he will be able to eliminate the problem.

Modifications and Mutations:
A number of elements can cause changes in color and conformation in Budgies (and other animals and plants). For example, dyes in the food can cause or augment coloration of Budgies. (Some canary breeders use dyed food as the principal method of achieving red coloration!) The changes of color achieved in this way are called modifications. They cannot be inherited and disappear as soon as the cause--in this case, dyed food is removed.

Modifications can develop from special foods, shortage of food, influences of light and air, chemicals, and other artificial agents. They have the trademark of being impermanent; they disappear as soon as normal conditions are reinstituted. Mutations are different. Suddenly, there appears on the scene a variation in color or form that is indeed heritable. The reason is generally not known or provable.

In some cases, mutations can be induced. I have been fascinated by the trial conducted with flower bulbs by Dr. W.E. de Mol of Oud-Loosdrecht in the Netherlands. He has been able to induce mutations by treating bulbs with X-rays. He changed the composition of chromosomes in ways that generate completely new varieties, the Budgie tulip and the cyclamen tulip, for example.
What Dr. de Mol achieved with radiation can also occur in Nature, for one reason or another. The composition of the chromosomes is changed, leading to the development of a variation in color or form--the mutation. Mutations that are visible to the eye occur extremely rarely, although new evidence suggests that the number of mutations is greater than is ordinarily assumed. Most mutations are either invisible or go unrecognized.

If a breeder notices a desirable mutation in his birds that has some promise, he will, of course, try to establish this trait through further breeding. Most current color variations have been established in this way. The original green Budgie was changed to a blue variant through a mutation. What happened is that the mutant lost the yellow component of the original green, leaving blue. Loss of blue through another mutation produced the yellow Budgie.

Albinos also developed by mutation one that caused the Budgie to lose all its color. Other types of variations also are attributable to mutations. For example, in 1938 the late Mr. Van Dijk discovered a green male with a small yellow spot in the back of its head. He bred the first pied Budgie from this mutation by crossing the mutant to a lutino female. Further inbreeding developed the "Dutch pied" out of this mutation where blue Budgies have white spots and green Budgies have yellow spots.

When a breeder notices a mutation that he wants to develop further, the best procedure is to mate the bird with a suitable male or female. (For a color mutation, use a male or female of the mutant color.) You will get young that don't show the mutant variation. They are "split for mutants" that have the trait for the mutation hidden inside them By breeding them back to the parent that has the mutation, you get a succeeding generation that does show the mutation. Rigorous selection can maintain and improve the mutation.

Taken from the book "The Complete Budgerigar" by Dr. Mathew M. Vriends.
The original text of each article remains copyright of the author.


E-Mail: berniehansen@sympatico.ca



- TOP -

Hamilton & District Budgerigar Society Inc.