I was looking through pictures of cockatiel mutations, and I stumbled across this one. It looked rather unusual to me, so I wonder if any of you seen anything like this.



While the picture itself is in photobucket, it was used in another forum website discussing the possibility of an orange cockatiel. The user called this one "dominant pastel" and "black headed". It looks like some kind of "reverse pied" (as pieds seem to usually have lighter colored heads and darker colored bodies).

It looks like it's either dominant silver or emerald. These mutations are caused by completely different genes but have a similar effect. There are people who can tell the difference between them (or think that they can) but I don't claim to be one of them.

It looks like he might be pastelface too since his face color is fairly muted. It's an allelic mutation (big can of worms there lol), meaning that it's a different variation of the whiteface gene and interacts with it in a complicated way. It's recessive to the normal gene and lots of people think it's dominant to whiteface, but co-dominance with whiteface is really a lot more likely. You can read all about it here if you want to dive into nerd-level genetic topics: http://www.littlefeatheredbuddies.com/i ... lelic.html

My coloration mechanics article has some information on emerald and DS: http://www.littlefeatheredbuddies.com/i ... tml#dilute No pictures though, you'll have to go elsewhere for those.

After looking into it more, I found out that it's apparently a trait of single factor dominant silver cockatiels.

I've seen emeralds with and without it, so I'm wondering if in the case of emeralds, some have it and some don't? Either that, or those pictures had bad lighting. I'm pretty sure I remember the emerald male at the bird show didn't have the darker skullcap.

Do all dominant silvers have this? I see some pictures without it, but I think that might have just been a mis-labeling of the mutation, there.

The skullcap is something that develops with age in both mutations. The body color is more normal in young birds but it gets lighter over time while the head color stays about the same. I'm definitely not an expert on these mutations, but I get the impression that not all birds develop such a distinctive skullcap.

It can be difficult to tell the difference between a normal baby and a DS baby because the coloring is so similar. I haven't heard of this being a problem with emerald.

Hm, interesting. I wonder why it's just those mutations.

I also wonder if it has any relation to the darker upper half that a lot of cockatiels have.

I think that might just be a cockatiel thing though. It's quite common, though I've seen a few without it.

I wonder why those two mutations produce such a similar effect when they're completely different from each other. Emerald coloring is caused by faulty dendrites (the pigment-delivery tubes in melanin-producing cells), and apparently the melanin delivery gets more impaired with age so the body gets lighter. My best guess is that the melanin delivery is more effective in the head than in the rest of the body and that's why the head stays darker. But I have no idea why it would be this way.

Nobody knows what the mechanism behind dominant silver is, but it's definitely not the dendrites - they're normal. But yet it produces a similar effect.

The darker upper chest in normal cockatiels might be related to the way melanin-producing cells migrate in the embryo. They originate in the neural crest (future spinal cord) near the shoulder area and spread throughout the body from there. The upper chest isn't too far from the point of origin so it might get proportionally more melanocytes than some of the more remote areas of the body.

The pied mutation interferes with the migration of these cells, and the further the cells have to travel the more likely it is that they won't reach their destination. If you look at pictures of heavy pied cockatiels, you'll notice that a lot of them have a band of grey across the upper chest, but the rest of their front side is yellow/white.