How could/would you work this out?

[finchbreeder]

A discussion today led to a question. So here it is and you get to solve it. Hypothetically
You go to a breeder or dealer (it does not matter which as they have no idea about the genetics of the birds) There are a number of white breasted yellow back Gouldians for sale, and they are the most magnificent you have ever seen and at a brilliant price so you are inclined to buy. (the head colour is also irrelavant as this is hypothetical and does not affect the question) How do you tell if they are Australian or European Yellow? The only differences are the sexs and the ring round the head. In some the head ring is snow white, in some it is quite blueish.
LML

[natamambo]

If the ring is bluish it is a SF Euro Yellow. Otherwise it is more likely to be DF Euro Yellow unless the straw markings have been bred out, for these birds pair to a normal PB and you'll know straight up, if any SF EY PB appear it's not an AY.

The one exception to this is that an EYAY bird is easy to create and we don't really know enough about colours to identify for sure, so you'll need to cross mate with a known EY, any normals that appear prove it is both.

I suspect an EY that GaryH sold me last year may be an EYAY as this year after second moult just a few straw markings have appeared on her back....

I also have a pure yellow male, but he has a lilac breast which has the same effect as a white breast on EY colour clarity.

[finchbreeder]

This is a hypothetical situation. But it was bought about because of a bird who is OH WB Yellow cock with very blueish neck ring. When paired with OH PB GB hen who had a white chin spot they produced 3 daughters. All OH of course. 1 x WB Yellow
1 WB Green, 1 PB Green. Any suggestions as to what this makes him? I think I know but am seeking clarification for the owner who is not me. Repeating the question is hypothetical because I know the breeding of the bird in question but am trying to clarify something I am unsure about. And I thought if a Euro cock was Yellow back this made him double factor, as the single factor yellows actually have green backs? Feel free to set me right as there are still some aspects of these i am trying to get my head arround. Give me a nice straightforward recessive gene anyday. Thanks for the how to be sure suggestions, they are definately part of what i am trying to work out and a great help.
LML

[Misso]

This is a hypothetical situation. But it was bought about because of a bird who is OH WB Yellow cock with very blueish neck ring. When paired with OH PB GB hen who had a white chin spot they produced 3 daughters. All OH of course. 1 x WB Yellow
1 WB Green, 1 PB Green. Any suggestions as to what this makes him? I think I know but am seeking clarification for the owner who is not me. Repeating the question is hypothetical because I know the breeding of the bird in question but am trying to clarify something I am unsure about. And I thought if a Euro cock was Yellow back this made him double factor, as the single factor yellows actually have green backs? Feel free to set me right as there are still some aspects of these i am trying to get my head arround. Give me a nice straightforward recessive gene anyday. Thanks for the how to be sure suggestions, they are definately part of what i am trying to work out and a great help.
LML

ok, so cock bird is a YH/WB/SFY ( euro yellow ) but because he has a white chest his back turns yellow ( if he had a purple chest he would have a lighter green back ). making him appear like a DFY or kinda like an AUS Yellow.

Hen is a YH/PB split WB/GB- Split to Aus Yellow.

[finchbreeder]

Thank you Misso. That is the bit I could not get my head arround. How he could be single factor if his back was yellow. But it is the white breast that changes this. And as it happens he may be EY/AY because his dad was a WB Euro yellow and his mum was exactly what his mate is. (not the same bird just the same type) So if I am getting this right. The birds who have white neck rings are double factor, and those with bluish neck rings are single factor white breasts?
LML

[tims]

Might have missed something but ey is sex linked isn't it..so possible to get greens from ey paired to ay.

[natamambo]

Tims it will depend on the pairing. If the father is EY DF then all daughters will be EY and all sons will be SF EY. If the mother is EY and father is AY then 50% of sons and all daughters will be normal greens unless mum is also split for AY and 50% of sons will be SF EY.

[Tiaris]

It is sex-linked dominant.