As far as I understand, they do. I was told by a local farmer not to use them for garden beds where edibles were to be planted. Unfortunately, the previous owner of this property we're on, used them as fence posts. Or, he planned to. There are cross ties sticking up out of the ground on the border of the front pasture. He never got the fencing material attached before they got foreclosed. He also used them as the corner posts for a 24'x24' dog pen, which is what we converted to the chicken yard, because it was already fenced and sat abandoned since 2010. From what I've observed, they don't bother with it. I see them pecking more at the weeds and other stuff. I personally, would not have used them in this manner at all because of the creosote and the risk of pecking, but we just went with what we already had. I think this is a really great question.I have a friend looking to build his first coop. He has some cross ties that he had left over from framing a flower bed, and was wondering if he could use them as basing for his coop/run. Then he wouldn't have to burry 4x4s and such. Save time and money. My concern is IF they have creosote in/on them. Would that be an issue for chickens pecking at the wood, or even rubbing against them? I told him I would ask my "chicken people" and see. I believe he wants to lay them on top of the ground as his ground base and frame up from there
edited to add: I decided to search and found this thread:
https://www.backyardchickens.com/t/194986/railroad-ties-safe
I may have to rethink the decision to place the coop where we did. We're sort of stuck with it now.

and this one, too:https://www.backyardchickens.com/t/101307/railroad-ties
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