by Brian Keenan
[From CAGE & AVIARY BIRDS ©]
Week ending August 11, 2001
BRIAN KEENAN EXPLAINS WHY CINNAMONS APPEAR IN A STUD OF BIRDS AND THE FACTOR RELATING TO THEIR APPEARENCE
I was reminded recently of a telephone conversation between two very well-know canary enthusiasts who were discussing cinnamons. "I've bred a decent-looking cinnamon hen, its parents are a cinnamon carrier cock and a green hen," said the first party. "Just a minute, let me check," came the reply, whereupon a rustling of papers could he heard down the telephone line. The verdict came back: "You're right, that hen you've bred must be female!" Cinnamons can crop up where they are least expected. This is particularly true when people breed from newly purchased stock and is why rumour has it that cinnamon can take over an entire stud, if not carefully kept in check. However, nothing could he further from the truth. The important thing to remember is that we categorically know the inheritance factors relating to the production of cinnamons. This is easily understood by following a few basic rules. If we believe we are getting different results, it is because our original assumptions on the genetic make-up of the parent stock were wrong, not that we have broken the laws of inheritance. There are only two possible birds that can cause confusion. These are carrier cocks which appear normal, but carry the recessive cinnamon factor in hidden form, and clear birds, of either sex, which cannot display the cinnamon feather coloration through melanin suppression, but which are nevertheless, true cinnamons.
To fully understand the cinnamon factor we must appreciate the rudiments of inheritance. Cinnamon is a recessive factor that is dominated by green, the normal plumage of the wild canary. The cinnamon factor is carried on the X chromosome, which, in combination with the Y chromosome, is responsible for determining a bird's sex. That is why breeders will sometimes refer to cinnamon as being sex-linked recessive.In simple terms, cocks carry two X chromosomes, one inherited from each parent. Hens carry one X chromosome, always inherited from their father, and one Y chromosome, always inherited from their mother. Genetically, hens are represented as XY, while cocks are represented as XX. In a cock, where both X chromosomes are the same, this bird will develop into a true breeding cinnamon or a true breeding green, while if one of these two genes has mutated, then the cock will develop into a cinnamon carrier, that is carrying cinnamon in recessive (non-visible) form. In this case, the bird is represented genetically as Xx. In the case of the hen, she carries only one chromosome, which must therefore be either a true breeding green or a true breeding cinnamon. There is no room for manoeuvre - the hen is either a cinnamon or a normal, she cannot he a cinnamon carrier.
So far, so good, we have only three types:
With these charts the only areas of concern surround clear birds. The cinnamon factor is a mutated gene, which removes the ability for a bird to express black, hence the appearance of red eyes when the chicks are first hatched. Variegation however, is controlled by factors for melanin suppression. The more factors present for melanin suppression will result in less variegation being displayed. This does not-mean that a bird is any less genetically a cinnamon, as the laws of inheritance still apply. Clear hens which are in fact cinnamons must have inherited the cinnamon factor from their fathers. They only inherit the (Y) chromosome from their mothers, and it has nothing to do with cinnamon inheritance. If they inherited the x chromosome, they would be cocks. So, different results from those expected among the young (which can be attributed to the hen) will mean that the hen's father was not what the breeder originally thought. He must have been a carrier cock or full cinnamon cock, in order to produce the hen in the first place! Similarly, clear cocks can also be either full cinnamons or cinnamon carriers, with full cinnamons owing their cinnamon inheritance to both parents, while carrier cocks could have inherited their single cinnamon gene (x) from either their father or their mother. The quickest way to prove the point is by pairing unknown clear birds into variegated stock. This will increase the chances of producing melanin pigmentation (variegation) in the offspring. A clear to clear pairing will continue to hide the cinnamon factor - and the colour is worth seeing, either as a ticked, variegated or full self specimen.
Cinnamon is displayed in the feathering as brown variegation. This is true of cinnamon ticks or grizzle markings, through variegated to full self and foul birds. .Where these markings are visually green, the bird is either a normal or a cinnamon carrier cock. .Clears can also be full cinnamons (cocks or hens) or cinnamon carriers (cocks only). They will produce exactly the same results as visual cinnamons, however they are paired, as the mode of inheritance is not altered.
With three types of cocks and only two types of hen, there are a maximum of 3 x 2 = 6 possible pairings:
Webmaster's note: Text typed by Jim Clever (thanks for that), images scanned by me!