The original link was no good, but I found the correct one: http://nwbackyardbirder.blogspot.com/2011/04/not-slate-colored-junco-cassiar-junco.html

If you scroll down to the comment by Mike Patterson, he suggests the "Cassiar" is a hybrid between slate-colored and Oregon -- and looking at the original blogger's photos, I think he is right!? It looks like an intermediate to me.

Jason Hernandez