There seem to be quite a few people on BYC aware of having one of those virus or bacteria you mentioned, and who manage to keep a closed flock successfully. And I've also read on a french forum that most backyard chicken keepers if they have been at it for sometime will get Marek's and / or some form of mycoplasma at one point in their environment.I've given up that idea. What I'm reading about acquired and inherited immunity puts a premium on old birds and their offspring, so the erstwhile candidates for culling will be staying and I'll stop buying in hatching eggs; if they don't make it to adulthood, they're not adding to the flock gene pool anyway. I think Phoenix sired Dyffrynand Killay
, at least, so some Penedesenca genes should be incorporated already; those two just need to make it to maturity and reproduction!
I still hope it was a coincidence, but it's responsible to act as if not

Zone 8, guess that explains the difference ! The ground does freeze here for maybe two weeks in January and usually that's it.Zone 5. We have to get it in before the ground freezes which doesn’t usually happen until November but I always play it safe and do it a few weeks earlier. What zone are you?
Like you I have difficulty to understand what intelligence means as an abstract concept, without applying to some specific notion : emotional, social, rational intelligence are all different.This is a very philosophical discussion. What do you all mean by intelligence? Not IQ as that was developed to test people.
No question that chickens are more intelligent than humans when it comes to a host of things around plant and insect identification and location, about subtle changes in weather and light, about flock members’ illnesses and a host of other things.
And they are certainly more intelligent about chicken flock social dynamics than we are!
But they don’t hold a candle to (some) people in solving simultaneous equations for example.
I think discussion of differences in intelligence between species is not a helpful frame of reference.
It is clear that chickens are intelligent beings with their own social structure and community, their own individuality, likes and dislikes. Surely that is enough to treat them with the respect they deserve.
I would personally like to think an important component of intelligence is the faculty to adapt to the environment, which would rank the human specie pretty low.
I have struggled for sometimes with the idea of keeping animals that are not meant to be eaten, but I can't imagine the alternative. Where would they live ? One could say we have taken for ourselves a big part of the place and made it unsuitable for others to live in.