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Cockatiels: Breeding Smart! Excerpt
COCKATIELS:  Breeding Smart!
by Linda S. Rubin
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Excerpt From Chapter 5:

Establishing Mutations

Inherited Mutations
Let's take a closer look at the definition of the term, mutation. According to biology,
evolution accounts for the occurrence of slight variations which have resulted from
successive generations of gradual change. The term "mutant," or "mutation," is the
sudden variation of an inherited characteristic. On the other hand, the term, "sport," in
breeders' jargon, refers to a variation which differs markedly from the normal but
cannot be inherited or passed on to future offspring. As one may gather, the operative
word is inherited.

Therefore, a credible or true mutation is one in which the mutant gene is successfully
passed along to the offspring. How then, is one able to tell if the mutant gene is
passed along? And, how many generations will it take before the mutation is
expressed visually? In other words, how many generations will it take for the mutation
to show itself? The answer to these questions lies in test-breeding.

The following paragraphs are excerpts from an earlier work by the author titled: "The
Complete Guide to Cockatiel Color Mutations," which are relevant to this discussion
and therefore worth repeating here:

"Not all characteristics are inherited by recessive or sex-linked modes, but it is a
good place to start. Generally, it is best to pair any new color mutation in question to a
Normal variety which, in the case of Cockatiels, is the (co)dominant Normal Grey. If
the young produced are all Normal Greys, we instantly know two pieces of
information. First, if the new color was inherited, we ascertain it to be recessive to the
Normal Grey. Second, if the new color is believed to be recessive, we then can
assume all the young to be heterozygous or Normal Grey split to the new color. In
order to prove this theory, father to daughter, or mother to son matings could be
attempted (using the mutant parent with its oppisite sex heterozygous offspring). This
type of mating would result in 50% visual mutants and 50% heterozygous or splits. Of
course, if no mutants are produced after several clutches, (for these ratios are based
on every 100 chicks produced), we can reasonably assume the variation is either not
recessive in reproduction or is only a sport and cannot be inherited as a legitimate
mutation."

"As you can see, proving the recessive mode of inheritance can take years of waiting
for birds to reach sexual maturity and test-breeding several generations. If one is
fortunate enough to produce a new mutation which is sex-linked in reproduction, it
certainly can be a shorter and often times quicker route to prove. If the mutation to be
tested is found in the male, it can be test-bred to a Normal Grey hen. This will produce
the mutation immediately in the first generation: 50% mutant daughters and 50%
heterozygous or split sons. If the mutation to be tested is found in the female, it too
can be test-bred to a Normal Grey male. However, this will now yield: 50% Normal
Grey daughters and 50% heterozygous sons split for the mutation. The split male
offspring will have to be mated back to the mutant Dam in order to prove the theory.
This should then produce 25% mutant males, 25% split heterozygous males, 25%
mutant females, and 25% pure Normal Grey females."

"It is important when test-breeding possible new mutations to try and pair them to
pure homozygous Normal Greys. In other words, birds which are not split to any other
mutation. There are several important reasons for this procedure. First, it is a
drawback when including other colors as often times these mutations may only serve
to mask or hide the new variant. In addition, some mutations may combine or alter the
new mutation in a significant way i.e., producing lethal genes, a less attractive color or
appearance, etc. Of major importance however, is the fact that in most instances, a
new mutation is going to be smaller, weaker and much less robust than an
established color. Therefore, by breeding the new mutation to pure Normal
bloodlines, you will begin to increase its size and improve its vitality, resistance and
fertility, by adding the vigor and strength of the established, stronger bloodlines."

"At this point, I must also warn against the hazards of inbreeding. I would definitely
forego the breeding of  ....    to learn more, order here
COCKATIELS: BREEDING SMART!
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The second edition in e-book format provides
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depth not often found in the literature.
*  NEWLY UPDATED SECOND EDITION
*  REVISED CHAPTERS on nutrition,
sports and new mutations
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   Excerpts:               Controlled vs Colony Breeding                      Breeding Condition                      Line-Breeding                     Inherited Faults                      Miscellaneous Faults                       Order >>