thank you; that's very helpful for clarifying that the dame is not pure.Genetic it's a pretty strait forward science, Out-crosses and Back-crosses are done to identify genes and mutations. If a solid lavender bird when cross to a partridge bird produces duckwing phenotype this means that the solid lavender bird in question is not pure for the Extended Black e allele.
The same pair also produced a pullet who is a month younger than that silver duckwing cockerel; can you tell from her phenotype what the dame's impurity might be?