This is just speculation, but I would rather doubt that deer-resistant plants equal chicken-resistant as well. Deer-resistant plants are mostly ones that the deer think taste or smell yucky (until the deer get hungry or bored, or a new gourmet fad sweeps through the herd, sigh). I do not get the impression chickens care much about taste, or about smell either unless something is quite aromatic indeed.
From watching what people write (I don't free-range mine), the plants that seem to survive around peoples' chickens seem to lean more to things that are mechanically-protected against chickens. Prickly, or with hard waxy leaves, or woody stems, or like that. And they also have to be able to tolerate scratching and digging around their roots.
Just a theory,
Pat