Much has been written about the sex linked factors and how they affect breeding expectations. However, most publications tend to become too involved, and except for a few who persevere with the subject, many beginners lose interest and pass it over. With this in mind, the following information is presented for those who want just a basic working knowledge of the subject.

 

First, however, we must very briefly cover the basic genetic make-up of a budgerigar. Like all living creatures, it has a certain number of pairs of Chromosomes.There are thirteen pairs to be precise. These chromosomes carry all the features that the bird possesses, i.e. shape, stance, size, feather type, spots, and so on. One pair of these chromosomes however are known as the sex chromosomes because these alone control that factor and it is this pair that we are concerned with when it comes to the sex linked features.

 

A cock bird has two 'X' type sex chromosomes. A hen bird has one 'X' and one 'Y' type sex chromosome. As the young only received one chromosome from each parent, you can see that it is the hen that decides the sex of the young, as the cock can only pass on an 'X' type chromosome.

 

Features that are said to be sex linked, can only be carried on the 'X' type. For the sex linked feature to be visible, it must be carried on both of the 'X' chromosomes in the case of cock birds, but only needs to be present on the one 'X' chromosome, when it comes to the hens. If a cock bird only carries the feature on one of the chromosomes, it is said to be split for that particular sex linked feature. With hens, if the bird does not show the feature visible, it cannot pass it on, no matter how it has been bred.

 

THE SEX LINKED FEATURES

At present there are six colours that are known to be sex linked; that is, carried on 'X' chromosome.

 

1. Albino

 

2. Cinnamon

 

3. Lutino

 

4. Opaline

 

5. Fallow

 

6. Slate

 

 

 

The last two are quite rare nowadays, so most fanciers are only concerned with the first four.

 

Having disposed of the basic genetic principles, let us now get down to the facts when it comes to breeding.

 

All you need to know is what you can expect to result from the pairing of these sex linked birds. The percentages of each possible outcome that you will obtain, can only be verified over a vast number of pairings. In fact it is doubtful if you could keep the birds alive long enough to even accomplish the necessary number of matings. As you can see, quoted percentages are purely academic.

 

RULES

If both parents are visual normals, then, if any sex linked young turn up in the nest, they will always be hens.

 

A visual sex linked hen must always be used if sex linked cocks are required. Although a split cock paired to a visual hen will produce visual sex linked cocks, there is no guarantee, so to be sure you should always use a visual cock as well as a visual hen.

 

Let us now consider the four sex linked features that are of most concern.

 

1. Cinnamon

 

2. Opaline

 

Both of these only have a modifying effect on the birds basic colouration.

 

3. Albino

 

4. Lutino

 

Both of these mask completely the basic colour. Albino masks the blue series of birds and the Lutino masks the green series. Further, if Lutino is paired with Albino, the Lutino will completely mask the Albino feature, providing there is no blue in the background of the Lutino.

 

RECOGNITION IN THE NEST BOX

Recognition of young sex linked chicks at the early stages of development can be made as follows:

 

Cinnamon

Up to 5 days old they have plum coloured eyes; after this they can be identified by the fawn coloured down as distinct from the darker normal coloured down.

 

Opaline

The down on these chicks is much lighter, being white in colour.

 

Albino/Lutino

Other than having white down they also have red eyes.

 

Information by S.B. Richardson

http://www.budgerigars.co.uk/charts/fallow.html

 

Isn't Fallow recessive rather than sex-linked?