Take a good look at pictures number one and two that accompany this column. Can you identify the mutations pictured in photo number one? If you came up with turquoise, congratulations are in order. Both birds are indeed turquoise, however, they are obviously not the same.
Now, look at the second photograph, can you identify these mutations? You would be correct if you identified both birds as gray-green. Again, one is slightly different from the other.
In photographs one and two, the birds with the lighter body coloring, flight and tail feathers are exhibiting an additional mutation characteristic. Unnamed, mis-named, mis-identified, overlooked and ignored, this mutation has been in American aviaries for at least 12 years, perhaps longer. It has been looked at, but not really seen.
Once pointed out, the mutation is so easy to spot thereafter, it makes you wonder how it ever eluded perception previously. The visual markers are unique. The overall body color is lighter and more yellowish. Brown melanin replaces black melanin as seen in the wild type green, blue, turquoise and gray-greens. The flight
and tail feathers are lighter. Although variable, a larger surface area on the flight feathers is colored like the body, and creates a subtle pattern. In heavily marked birds, the feathers look like they have been bleached. Open the wings and look at the flights closest to the body . . . the dorsal sides of the feathers are often marked with whitish "hash" marks perpendicular to the feather shaft.
The eyes, and the rings around the eyes of newly hatched and naked chicks are reddish, hut not as red as the eyes on the lutinos or albinos. As the chicks grow and feather-out, the eyes darken, and no longer look red or ruby colored.
This mutation is a form of cinnamon. It's an exciting mutation since it can he used to alter every other color including the wild type, or normal green. In pure white albino birds, the identifying characteristics are masked, but the presence of this form of cinnamon can still he confirmed through genetic tracking of offspring exhibiting the mutation.
Genetically, this mutation is a dominant inheritance type, meaning that at least one bird must visually exhibit the mutation characteristic in order to produce more mutation birds. There are no splits with dominant inheritance types. The theoretical expectation for production of mutation chicks using one visual parent, is approximately 50%. If both parents are visual with the same dominant characteristic, approximately three out of four (75%) of chicks produced will exhibit that dominant mutation characteristic.
You might be asking at this point, why don't you get 100% visual mutations when both parents are visual dominants? The answer lies in the genes of each parent bird.
Understanding the difference between heterozygous and homozygous is the first step:
A. When only one allele in the chromosome pair has the characteristic gene, the bird is said to be heterozygous.
B. When both alleles have the char-
acteristic gene, the bird is said to be bomo:rygous. (Note: Heterozygous and homozygous are occasionally called single factor and double factor, respectively. However, single and double factor are not specific enough terms, and therefore won't be used in this discussion.)
In order to produce 100% visual offspring for a particular dominant characteristic: both parents must be visual, and one or both parents must be homozygous for that mutation characteristic. That sentence is a mouthful.
Don't feel bad if you have to read it over several times allowing the information to sink in.
Unfortunately, it's not possible to visually identify heterozygous and homozygous chromosome types. DNA studies will answer these questions some day with a simple blood test, but for now, the identification of heterozygous and homozygous birds requires test mating, perhaps for many seasons. Positive identification for heterozygous is easily accomplished. Homozygous is more difficult. This aspect of genetics
will be covered in a future issue.
Now that this cinnamon-type mutation has been visually and genetically identified, we need a name. It has been called cinnamon, Isabel, and more recently fallow.
Cinnamon occurs in three different inheritance forms, dominant, sexlinked and recessive, so just saying "cinnamon" is not descriptive enough. Isabel is an European term, which is now virtually meaningless here in the U.S.A. because it's been used to describe anything resembling cinnamon, regardless of the inheritance type. Fallow is the name generally given to a red-eyed, recessive cinnamon mutation.
Since none of these names seem to be appropriate, how about recognizing the mutation as dominant cinnamon? This is a name that is not too fanciful, and yet clearly identifies the mutation visually and genetically.