Yellow Heads what are they realy?

[KENTUCKY]

A lot has been written about yellow heads and a lot more to come I am sure.
At times yellow heads are being referred to as mutations or even a third species of Gouldians , nothing could be further from the truth in my mind.
The well known English Gouldian breeder Percy W. Teague together with the help of the well respected research scientist Dr.H.N.Southern, worked out the Head colour inheritance of the black heads and redheads. When Raymond J.Murray learned of this through an article in an engish medical journal, started to correspond with these two Gentlemen, struck up a friendship and exchanged information on the Gouldianfinch.Yellow heads where not known or not available during the second world war in England. Teague probably found it very difficult to obtain seeds for his beloved gouldians just to keep them going and to breed enough numbers to determine the genetic outcome of the various youngsters, mortality rate in young gouldians was very high those days,as antibiotics where not known as we know them today.
although Teague had his back to the wall, in terms of supplies but, together they managed to breed enough youngsters to be able to determine headcolour, sexes and ratio.
It was done like this, to beat the high mortality rate, a lot of head feathers and chest feathers where plugged and within six weeks adult plumage would replaced juvenile feathers, sex, head colour and ratio was then be revealed.
When R.J. Murray of Australia pioneered the genetic make up of the yellow heads by crossing these with the other two head colours, he took the opportunity to double check Dr H.N. Southern's conclusion and found that his results could not be faulted.Murray not only discovered that the factor for yellow headedness is autosomal recessive and independent of the sex linked factor which controls the gene for red and black headedness, but also with the assistance of three bird breeding mates, one a GP, one a canary breeder and one a budgie breeder, all three specialised in genetics ,between these four people worked out that yellow heads are actually modified red heads.Yellow Headedness is caused by a gene defect that prevents the bird from transforming yellow food substances into red.
Yellow and red is dominant to black but, when a pure yellow cock bird is mated to a red hen and vice versa ,yellow is treated as an equal strength colour factor because the progeny (youngsters) from both pairings are identical. If this was not so then there would be no yellow today because Murray used red in all his matings to produce his strain of yellow heads and if red were dominant to yellow then yellow would have been lost by continuous interbreeding with redheads. According to the normal law of inheritance it is therefore not possible for a bird to carry three different headcolour factors, and with this in mind and yellow being an equal strength colour factor, Murray re-located the factor for yellow to its correct place from red/black/yellow to red/yellow /black. I still have some posters depicting the Inheritance of Headcolour in the Gouldian Finch, I used colours to discribe the 54 matings on my poster, a very educational and informative poster for novices and seasoned breeders alike, genetics in an almost childsplay presentation, that will be an evergreen unlike posters of mutations.

[Diane]

Thats very informative, thanks. Its great to have so many members with knowledge of genetics.
I would love to see the posters you mention.

[natamambo]

Kentucky, I've read your post several times to digest it before responding and I must say I agree that yellow head modifies red head (when both alleles present). However it also modifies black head through the production of the yellow tipped beak and as a result a few of your statements have me bothered as potentially misleading:

At times yellow heads are being referred to as mutations or even a third species of Gouldians , nothing could be further from the truth in my mind.

This depends on your definition of "mutation" but if there is a source genotype then yes it is a mutation. Most geneticists, on the basis of wild flock ratios, consider red head a mutation and black head to be "wild type", the only reason it is not rare in the wild (as most mutations are) is that somehow it is dominant over wild (black) but not lethal. On this basis red hair in humans is also a mutation. So now the real question is what is "normal with variations" and what is "mutation" (I bet my brother and nieces don't consider themselves as redheads to be mutations).

According to the normal law of inheritance it is therefore not possible for a bird to carry three different headcolour factors

Yes, but it is possible for a cock to be red head split for both black and yellow so I'm not sure what you mean by "carrying three colours" as that implies a fourth colour.

Murray used red in all his matings to produce his strain of yellow heads and if red were dominant to yellow then yellow would have been lost by continuous interbreeding with redheads.

He must have had a yellow somewhere to start with and after that it is chance. Yellow may skip generations but it would not disappear ("lost") just ask the many people who get a most unexpected result in human "breeding" when a very rare genetic condition shows up (we have an example in our own family, 1st wife and 4 kids fine, 2nd wife and hey presto condition X appears, all that was needed was a random pairing that might never have been). Red is dominant to yellow as the bird (regardless of sex) must have two alleles for the change to occur. Yellow is also recessive to black as when both alleles are present the beak changes colour - the only reason the head can't change colour is that it has already lost the ability to make red in the feathers and yellow is not a change in colour (as red to black is) but rather the inability to totally produce a colour (so what you really have is a kind of "watered down" red).

What fascinates me, and to my mind needs further study, is - why a bird can be deprived of red in the feathers (and thus have a black head) but still produce red in the beak yet it can also be deprived of all red? I can't help but wonder if another gene is at work, one controls feather colour (yellow or not yellow) and the other controls beak (yellow or not yellow) but for whatever reason the yellow beak requires the yellow head to chemically "switch it on".

However, your post did cause me to think what happens with a yellow + black pairing and you are right in yellow being a modified red as the literature all agrees this will produce red offspring unless the black is a cock and is also carrying yellow in which case you'll also get yellow split for black.