Okay, forgive me for asking a stupid question, but if most all birds have CRD, and they can become 'immune' to it through the egg, wouldn't it be better for all birds to have it? It seems like CRD is not necessarily a killer, except for maybe a few, and it is not passed on to humans, or any other mammals, for that matter. So wouldn't it benefit the birds to be immune to this? Especially since it can be transmitted by wild birds?