Song Inheritance

Posted: Mon Mar 05, 2007 12:37 pm Post subject: Shama Song Inheritance

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There has been some discussion in this forum on whether the shama’s song ability is inherited or it can be acquired by suitable training. One of the books that has assisted me a great deal in breeding and maintaining my shamas, is not a book on shamas or even of soft-bills but on canaries. While Linda Hogan’s “Canary Tales” is about Roller Canaries, there is much in the book that is applicable to other species. Below is an extract on the song inheritance of canaries which I have applied in my breeding program. By applying, and continuing to apply, Linda’s methods, I hope to eventually breed a super strain of shamas that is more desirable than anything in the wild. For breeders who would like to consider what is required to produce good songsters, I quote below from Linda's book:

How well a bird sings depends on its inheritance. It is estimated that 75% of the birds singing ability is inherited, while 25% of the singing ability is due to training. Since song is inherited as a sex-linked characteristic, to improve the song we must be able to identify the genetic contributions of both the cock and the hen. Sex-linked characteristics are carried on the x chromosome. The song the bird sings is dependent upon the genetic makeup of the two x chromosomes inherited one each from the father and mother. The female canary has one x chromosome and one y chromosome. Her x chromosome was inherited from the father and the y chromosome from her mother. Each male offspring of the hen will inherit the x chromosome she inherited from her father. The cock, in contrast, has 2 x chromosomes, one he inherited from his father and one he inherited from his mother. Male or female offspring have an equal opportunity of inheriting either the x chromosome of his father or the x chromosome of his mother. …… Even though the offspring have the same parents different song patterns are expected because of the combination of x chromosomes inherited from the mother and the father.

The practice of line breeding is one way to improve your bird’s song. A “good” singer can be selected and bred back to its mother. …. When we breed the son back to the mother we increase the mother’s contribution in half of the males as well as reproducing the mothers x song type in half of the females. By evaluating the sons we get a good idea of what the female is contributing to the male offspring’s song.

To get a closer look at both of the father’s x chromosomes we [breed] him back to several daughters and compare the sons’ song…..

Once the appealing combinations are identified, further line crossing can be made to improve the beautiful song. Utilizing half brother/sister combinations, weave a pattern that balances a cock who is strong in bass with a hen whose father was strong in hollow roll and vice versa.

When purchasing breeding stock buy from one breeder who is consistently winning on the show bench. Avoid the temptation to buy unrelated birds from different breeders. Always breed within a strain. When an outcross is necessary return to the same breeder. Only when a suitable outcross is not available, is it necessary to buy an unrelated bird. This unrelated bird should be pure and from a compatible strain. Do not breed males from this pairing because they will not breed true. Rather keep the daughters and breed them back to your original line. Many breeding disappointments can be avoided by always making sure that the breeding male is your pure strain. Outcross males may perform very well on the show bench, but only disappointing results happen when you breed them!

Posted: Thu Mar 08, 2007 12:30 pm Post subject:

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Pak David

This one just a correction to Lindas's book. Maybe I am wrong, but I feel I will not wrong because it was a valid knowledge.

She said..."female has one x chromosome and one y chromosome... etc."

In my memory in genetics (Mendel's Law of heredity)... it is a male who has XY genotype and female has XX genotype. So if one male breed to a female, the zygotes bring their parents characteristics (good and bad -dominant (visible) and recessive (not visible) in their chromosome. There are many chromosomes which responsible to bring each of those characteristics.

Example :
female could be xX, XX, or xx let say X = gen for long tail
x = gen short tail
male could be XY X = gen for long tail

Note : characteristic is linked in x chromosomes so Y just indentification for male.

So if we breed a long tailed female, she must has genotype xX or XX but will not xx. (other characteristic will linked in other chromosome; for example human has 46??? type of chromosomes? (if I am not wrong?)

Possibility of their offsprings from xX female are :

X vs X -----> XX born new female like mother (50 %) long tailed
x vs Y -----> xY born new male with short tail (50 %)

Possibility of their offsprings from XX female are :

X vs X ------> XX born new female like mother too
X vs Y ------> XY born new male like father

The same matrics can be used to predict a particular characteristic genetically.

This is just my opinion as comparison... thanks

Regards
Ghozze
Posted: Thu Mar 08, 2007 2:30 pm Post subject: Gene inheritance

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Hi Ghozze,

The sex of a mammal is determined by the nature of the sex chromosomes that it has. In mammals the male will have an X chromosome and a Y chromosome (XY) while the female will have two X chromosomes (XX). The opposite is true in birds where the males have XX chromosome and the females XY.

The extract that I placed on the Forum sets out only the very basic principles of gene inheritance with regard to song in birds and possibly other characteristics associated with it, such as display and aggressiveness. It shows that in the planned breeding of birds, the role of the female is likely to be more important than the male to obtain the traits of song that we want. Let me clarify.

Every bird has 2 chromosomes that determine its sex – one that it inherits from its father and one that it inherits from its mother. A male will have two X chromosomes while the female will have an X chromosome and a Y chromosome.

It is the mother bird which determines the sex of the chick. The father cannot determine the sex of the chick as, being male, both its sex chromosomes are X. Consequently, it will always pass an X chromosome to the egg upon fertilization. The female on the other hand, has an X chromosome and a Y chromosome and the chick’s sex will be determined by which of these is in the egg. If the egg has an X chromosome from the mother, the chick that hatches will be male as the egg will invariably receive an X chromosome from the father upon fertilization. If the egg contains a Y chromosome, the chick will be female as the Y chromosome will combine with the X chromosome from the father to produce a female.

From the above it will be seen that the X chromosome that the mother passes to its chick will always have been inherited from her father. Consequently, if we later breed this first generation female chick (F1), we know that the X chromosome that it passes to its egg will have been derived from her father. On the other hand, the first generation male (F1) will have two X chromosomes, one that it received from its father and one that it received from its mother that she inherited from her father in the wild that we know nothing about.

For the above reason, if we are just starting to breed shamas and want to propagate the bloodlines of our favourite male, we are more likely to succeed if we breed from the F1 female progeny rather than from the F1 males.

The position is much improved with the 2nd generation offspring (F2). An F2 female that is bred back to the grandfather will result in more of the grandfather’s genes in the offspring (F3). The egg from which the F2 female hatched will have received an X chromosome from the grandfather. The F2 male offspring will also have received the grandfather's X chromosome through its mother and the grandfather's X chromosome directly from him through the mating to its mother. In other words, both the X chromosomes of the F2 male and the X chromosome of the F2 female will be those from the Grandfather.

As an example, let’s say we are just starting to breed shamas and our aim is to breed the best that we can. Through much effort, we have acquired a beautiful long tailed wild-caught male and we mate him to the best wild-caught female that we can get. The male will pass one of his two X chromosomes to the chick (F1) and hopefully, it will be the chromosome that contains the song characteristics that we want in the progeny. The female will pass her X chromosome (that she inherited from her father) to the male offspring (F1) and her Y chromosome to the female offspring (F1).

If we then breed from the F1 male offspring, it will pass to the egg, either the X chromosome that it received from its father (our favourite bird) or the X chromosome from its mother that she inherited from a male shama in the wild that we know nothing about and which may not have the characteristics that we desire. Breeding from the first generation male offspring will therefore result in more uncertainty in the product that we will get. For this reason, it is preferable that we breed only from the F1 female offspring and not the F1 male offspring.

By using only the F1 female and breeding her back to her father or a close relative of her father, both the male and female chicks in the 2nd generation (F2) will have more of the genes of our favourite bird and we can then use the the males and females from the F2 generation in our breeding program.

As you have noted, the results of breeding are variable and very uncertain and a great deal of luck is required if we are to be successful. Knowing the principles of breeding will help to stack the cards more in our favour.

David