Sex-Linked Yellow Cheek is a sex-linked recessive mutation that inhibits the production of the orange psittacofulvin in the cheek patch leaving the cheek yellow. This mutation to date is unique to Cockatiels as there are no other sex-linked mutations under parrot species that alter psittacin in this way.

This mutation was established in Germany in the 1990’s and is widely available around the world.

There are multiple variations in the cheek patches that are produced from this mutation and these variations are very similar to the Paleface/Pastelface and DYC (Dominant Yellow Cheek) mutations. Pairing these mutations together would result in confusing and unexpected breeding results as none of these mutations are alleles of one another regardless of their similarities.

This mutation combines well with all mutations that reduces/alters melanin. Pairing this mutation to any mutation which removes/alters psittacin would be undesirable as most psittacin altering mutations would mask the presence of this mutation and could result in this mutation being carried over for generations with no indication whatsoever.