A dramatic increase in Cockatiel olor mutations over the last ecade has spiraled forth a plethora of myriad color combinations. It is no longer a simple task to outline or discuss individual Cockatiel mutations, as the number of colors and patterns continues to grow, challenging Cockatiel breeders and enthusiasts to keep pace. One paper cannot begin to cover each individual new mutation, and its now multitudinous combinations, to the depth and degree which would do each one justice. Instead, this paper will limit its scope to discussing each new major mutation by category, and attempt to provide a basis for which the mutation can best be understood, and applied to the growing number of cross, triple and multiple color combinations.
Mutation Modes Spontaneous Mutations
Mutations commonly arise in aviaries under one of two conditions. In the majority of mutations, the affected trait usually occurs as a sudden variation of an inherited characteristic. Such color mutations are usually a welcome surprise to the breeder and are so different or obviously deviant, that anyone slightly familiar with the basic colors will recognize its unnatural and anomalous appearance almost immediately.
The second less commonly seen mutation which must be considered is the gradual appearance of an unusual trait which, through painstaking work
and diligence, arrives at its final form only after many years of work. This gradual and timely process which the aviculturist controls by deliberate pairing of affected individuals, is better known as selective breeding. For example, the deliberate pairing of very yellow Pied stock, correctly linebred, will usually yield a predominant strain of heavy yellow "golden" Pieds.
The majority of Cockatiel mutations, until very recently, dealt only with autosomal recessive inheritance (ie. Pied, Fallow, Recessive Silver, Whiteface, etc.) or sex-linked recessive inheritance (e.g. Lutino, Cinnamon, Pearl, etc.). More recently, with the advent of the U.K.'s new Dominant Silver mutation, a new mode of inheritance in Cockatiels was introduced known as the dominant mode of reproduction. What makes dominant inheritance even more interesting is the appearance of both single factor and double factor birds which, like any other mode, is predictable by Mendel's laws of inheritance.
More specifically, Mendel's law of dominance states that one factor in a pair of traits dominates the other in inheritance, unless both factors in the pair are recessive. This works as well for any mutation or trait recessive to the Normal Gray (i.e. including both recessive autosomes and recessive sexlinked traits), but takes on new meaning for dominant, codominant and partially dominant mutations. Although the dominant mode of inheritance is new to Cockatiels, dominant inheritance is routinely worked within other species in aviculture, including
Budgerigars, lovebirds, Indian Ringnecked Parakeets and others.
For the purpose of this discussion, we will divide Cockatiel color pigments into two major groups.
The first group, melanins, is comprised of the darker or shaded pigments· as found in the ground colors of standard mutations e.g. gray, cinnamon, silver, fallow, etc. The second group, carotenoids, is composed of the red-yellow-orange pigments occasionally referred to as lipochromes. The third listing is simply headed as white which, for the sake of this discussion, is the absence of pigment and is therefore simply, the absence of all color.
• Melanins: any of the group of darker or shaded pigments, e.g. gray, cinnamon, silver, fallow, etc. Melanins may vary in shade and intensity which breeders commonly refer to as the lack, or presence, of dark factors.
• Carotenoids: any of the group of red and yellow pigments, often referred to as lipochromes, when discussing orange and yellow coloration.
• White is the lack of pigment or absence of all color.