Last section we covered the most basic of the relationships we have to study.  The dominant to recessive relationship sets the pattern we will use in the following articles with the exception of a little change here and there.

This month we are going to look at some more dominants and see how they affect colour.  There are those that we say modify the penetration of  the original colour and there is the second group which we say  modifies the intensity of the original colour.  We will look at these separately and see how they are similar and how they are different. 

Penetration Modifiers:

We will start off by looking at the Penetration Modifiers.  Examples of these are the grey, violet and dominant pieds in the budgies and the dominant silver in the zebra finches.  For the purpose of this demonstration, I will use the  grey factor in budgies as the example, since it is the easiest to visualize.

Let us start off by remembering that all birds are normal in colour, normal being light green budgies, normal zebra finches, normal cockatiels and normal lovebirds.  All budgies are really all light greens, keeping it in mind that green is made up of a combination of the colours yellow and blue.  A blue budgie is really a green budgie minus the yellow  and blue.  A blue budgie is really a green budgie minus the yellow pigmentation leaving the only other colour left, which is the blue.  If you look at this closely you will see that the mutation gene that gives you a blue budgie really is just taking away the yellow from a green bird because the blue has been there all along.

The next point I wish to make is that penetration modifiers are dominant.  They basically follow the same set of rules we looked at last month with one new twist.  Birds being influenced by this mutation can have it in single dose or double dose, and they both look alike.

Let us look at the Colour Modifier Chart and go through it to better explain the above comments.  In last section's chart you will notice that the parents are on the left and the four different combinations of chicks are on the right.  To keep it simple it is also important to remember that all the birds in this chart are normal (light green budgerigars). The two clear boxes represent a normal bird with no modifiers.  The combination of one dark and one light represent a normal bird, with one dose of the modifier while the two dark boxes represent a normal bird with a double dose of the modifier.

Now let us look at some of these scenarios. If you look at the line 1, you will see two birds with no modifiers, producing chicks with no modifiers.  This is simple, since the parents have no modifiers of their own, they cannot pass any to their offspring.

Next look at the line 2, and you will see that one of the parents has a single factor and has passed it on to half of his or her offspring.  Check the difference between this line and line 3 where you have a “double factor bird” with a “no factor bird.”

line 5 shows that a parent with one factor and a parent with two factors will give you half the chicks with one factor and half with two factors.  All these chicks look the same.  You can only tell the difference between these birds by breeding them.  If any of these chicks produce no factor birds when they are bred, then these birds have to be single factor, as is the right hand parent in line.

This is all fine and dandy, but how does this relate to the living bird?  Let us go back to our example, the light green budgie.  In our chart, all double white boxes represent  light green budgies which have on modifier factors (they look light green).  The boxes with one white and one dark box represents the birds with one factor of the modifier.  This factor modifies the PENETRATION level of the light green and it becomes grey green, or a single factor grey green (they look grey green).  The boxes with two dark boxes represent birds with two grey factors.  These are called double factor birds and they too modify the penetration level of the light green to make it also a grey green or a double factor grey green (they too look grey green).

The big thing to remember with penetration modifiers is that a single factor bird and a double factor bird look identical.  The only difference is in their breeding results.  You can see this difference when you compare lines one and two where the parent on the left is single factor in line 2 and the double factor in line 3. Likewise you can compare lines 4 and 5.

Intensity Modifiers:

The intensity modifiers are very similar to the previous penetration modifiers in that they are also dominant and use the same chart and follow the same rules, with one more twist.  Because the colour intensity is now being changed, we actually see a difference between the single factor bird and the double factor bird.

The most familiar example of intensity modifiers is the dark factor, which we see in dark green and olive budgies, in cobalt and mauve budgies, and in peachface lovebirds displaying these same colours.  We can use the same chart to study this group as we used to look at the penetration modifiers, with keeping in mind that one twist.  The difference here is that the birds with one dark box look different from the birds with two dark boxes.  In other words a single dark factor bird looks different from the double dark factor bird.  Referring to our budgies again, we have a light green with no dark factors, a dark green with one dark factor and an olive with two dark factors.  Applied to peachface lovebirds we see the pastel blue with no dark factors, the cobalt with one dark factor and the mauve with two dark factors.

Let us now assume that all birds in the chart are blue.  Looking at line 2 in our chart we see that a blue bird mated to a cobalt will produce half blue and half cobalt.  While in reality they are all blue, the cobalts just have a more intense blue.

Line 3 tells us that if we want to breed cobalt in great numbers, we should breed a blue to a mauve because all the young are cobalts.  This pairing cannot produce a blue or a mauve bird.

Please remember that with both the penetration modifiers and the intensity modifiers being dominant, the bird must show it, if it has it.

This section on intensity modifiers would not be complete without mentioning an exception which is found in budgerigars.  You may wish to read this at a later date after you have had time to digest the preceding, because it will tend to cloud the issue.

The single dark factor in budgies (and maybe other species such as peachface lovebirds) comes in two different forms when we refer to dark green/blue.  These are referred to as Type I and Type II and only apply to the dark green/blue.  The difference lies in which parent the dark factor came from, and it affects the percentage of each different colour of young produced.  This is a subject that will be covered in more detail in the 6th and final part of this series of articles.

KEY POINTS TO REMEMBER:

1.  A bird with a colour modifier can have it in single factor or double factor doses.

2.  Modifiers do not give a different colour but only alter the birds original colour.

3.  Penetration modifiers look the same in single or double dose.

4.  Intensity modifiers look different in single or double dose.

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