Rare Cockatiel Mutations
Another one of those rare cockatiel mutations which is not talked about a lot is the thrush-chested cockatiel.
This is another mutation with only a very slight significance. The affected cockatiel has some of its chest and belly feathers with a reduced amount of melanin, so they give a speckled chest to the bird. In rare cases some of these cockatiels also have spotted heads.
As the opaline mutation does not pearl the feathers of this are, a more attractive bird is produced by combining these two mutations.
Here is another interesting article about Thrush-Chested Cockatiel.
You can also see some incredible pictures at the link above of this rare cockatiel mutation.