Aussie Finch Forum

Touche to that.
A prominant Gouldian researcher was recently asked something about yellow-billed Black-headed Gouldians after a lecture at a bird club on the above research. She was totally unaware of the existence of this natural form of the Gouldian. This points to the depth of the lack of understanding of the subject.

Wasn't meant to be a 'touche', but an agreement with that point, which others seemed to be refuting

The touche was to the point that aviculturist knowledge would be useful to the ornithologists. You just beat me with the reply.

arthur wrote:

Tiaris wrote: The more generations you go down, the greater the proportion of the trait with the dominant mode. .

To me that is axiomatic . .

And

Price fluctuations (falls) in mutations of both parrots and finches also bear this out

Sorry guys, but without any selection pressures this is simply untrue. Mathematically the proportion of each allele within the population remains stable indefinitely - this is not a theory it is a mathematical fact. I don't claim to be an expert on evolution or inheritance but I'm pretty good at doing my sums!

There are selection pressures operating all the time in captive stocks but how this affects head colour frequencies I'm not sure. There are periods when some head colours are more popular than others, I imagine. Personally, I prefer BH and YH not RH !!

One thing, though, frequencies will remain stable in a population given random mating. This definately does not happen in aviculture but does it happen in the wild?

If you believe the story, selection pressure does happen in the wild too & it happens in a way which not only favours same head colour pairs but actually benefits these pairs by greater reproductive success. If this is a factual finding, this would favour selection against BH as it would give BH genes less prospect of infiltrating the RH stock successfully. If you also believe the RH dominance theory, this should dramatically exascerbate the odds further against BHs. In reality this is clearly not the case.
Sam, I accept your idea that the BH alleles are carried forward indefinitely, but the RH's dominant mode of inheritence means that where the BH gene coincides with the RH one (which is only possible in males) the birds phenotype is always going to be RH, ie. it will be RH whether it carries the BH gene or not.

SamDavis wrote: . Mathematically the proportion of each allele within the population remains stable indefinitely - this is not a theory it is a mathematical fact!

The proportion remains stable . . I can accept that . . genes cannot disappear during transmission

Now the hypothetical:

100 dominant genes spread over 100 birds = 100 single factor 'coloured' birds at best or 50 d.f. 'coloured' birds at worst

100 recessive genes spread over 100 birds = 50 'coloured' birds at best or 100 'UNcoloured' birds at worst

Proportion remains stable but 'coloured' birds with the dominant genes are taking over numerically