I get lots of columbians in my birchen ameraucana project. What I have been told by another breeder is that silver basically a columbian gene linked with an extended black gene, thus turning the white body black with silver hackles. Remove the extended black and you have a columbian.
Don't quote me on this, I am no expert on how colours work, I know some basic stuff but once you get into details like that I kinda sorta get it but don't at the same time. Seems to make sense to me, certainly explains the columbian coloured chicks I keep getting.
I have crossed silvers with blues and blacks and crossed the most birchen looking offspring of that and get some quite nice columbians. I had about 6 hens over the past 2 years, beautiful columbians with nice beards, blue legs, blue eggs and almost clear markings. Just a hint of salmon colouring in the chest area but thats it. I hatched a couple dozen columbian type pattern birds but those 6 were the cleanest in markings and just stunning.
If I liked that pattern I would have changed from Birchen to that(2 yrs ago I got 3 columbian coloured chicks for ever 1 birchen coloured one....), but I gave all the hens to a friend who wanted some blue egglayers.
She kinda distributed them all over with her constant requests for unique looking laying hens.