The following are excerpts from various source including my own experience regarding practical canary breeding.
Variegation in Color Breeding
A friend from this list emailed me asking how I control
variegation on my canaries. He was told to NEVER breed a clear (lipochrome)
canary with a self (melanic) canary. That is true if you intend to show your
birds, as only a complete-colored (or not colored) canary can be judged as "colorbred".
(There are breeds that accept variegated canaries as show birds). The
reason for this rule is that variegation is controlled by several genes thus
very difficult to write it down on paper.
He asked me to repeat to the List what I told him.
Let's start by assuming variegation is controlled by only two genes; the E gene
representing "clear" and the E+ gene representing "self". Since all birds have
two genes, a clear (or mutated) bird will be EE, a self (or wild) bird will be
E+E+ and a variegated bird will be E+E. Let's call them F1 and
cross them:
Clear and clear (EE and EE) = 100% EE (all clear birds)
Self and self (E+E+ and E+E+) = 100% E+E+ (all self birds)
Self and clear E+E+ and EE) = 100% E+E (all variegated birds)
Simple, eh? It gets complicated. Let's cross some of the variegated babies and
call them F2:
E+E and E+E = 25% EE, 50% E+E and 25% E+E+
Note that some of the new variegated F3 babies will be ticketed (lightly
variegated), some will be foul (heavy variegation) but at least half will be as
the F2 parents. There is even a small chance of getting either a few clear or a
few self babies.
Now crossing the clear F1 parent with one of the variegated F2 or F3 birds we
have:
EE and E+E = 50% EE and 50% E+E
Note again that the variegated progeny will have variegation all across the
border.
The same happens crossing the self F1 parent with one of the variegated F2
or F3 babies:
E+E+ and E+E = 50% E+E+ and 50% E+E
The conclusion is: the clearer the parents, the clearer the babies (or more self
birds if that's the way you cross them). If you know what you are doing,
crossing between lines is a wonderful way of instilling new vigor to an old
line.
Dilson/Miami/