no, but if I understand Ball aright, that (and many other) mutations is what the genome does (not simultaneously, just routinely). Reproduction is not replication; RNA is not a biological photocopying machine.Did it indicate whether the mutation came from a single bird? I can't see the same mutation popping up in hundreds of carefully maintained heirloom breeds simultaneously.
I don't know that heirloom breeds, carefully maintained or otherwise, are relevant. What is your point?