We have owned many a loveable JRT...they are one of our favorite breeds.
They LOVE chickens, but not to snuggle with haha. We never could break ours of doing all they could to munch on the escapees from the coop. You could be right on their tails as they chased the poor doomed poultry and they would care less about your admonishions to cease and desist.
Our Aussie, though...he's a GEM. He'll herd them back into the coop when they escape...and even when he's panting hard, he will close his mouth and gently push them to go the direction he desires. No matter how frazzled the chicken becomes, he never gets too excited to forget to be gentle.