Black beak???

[bluebutterfly213]

I have just been watching my young male gouldians, they are two thirds coloured up now.
I noticed that one of the YH PC GB had a black beak my first thought was I had mistaken the sex and the bird was a hen and I had put it in the wrong cage.
This bird with the black beak is definitely male, same strong colouring as another male bird from the same parents. Other siblings with YH (hens and cocks) have the ytb

Father is
YH PC GB

Mother is
RH/YH PC GB
This is as much as I know about the breeding of the parent birds. I only know the hens is split to YH due to the colour of some of the babies.

This pair over 3 clutches has produced
4 RH/YH cocks with red tipped beak
1 RH/YH hen with red tipped beak
1 YH hen with ytb
2 YH cocks with ytb
and the bird in question YH cock with btb

I have checked with a couple of the genetic forecasters and they mention the YTB but not a BTB.
Any thoughts about this?

[nixity]

I have a black head male that after he started raising babies, so was in peak breeding condition, his beak turned an almost purple color - it is very dark.

I don't really think it means anything genetically, though.. I think some just get darker than others.

[bluebutterfly213]

Oh well, I was thinking but didnt want to hope too much that I might have picked up a split to blue somewhere in the line.