My dogs and my chickens have always free ranged over our property. Yes, that's right, my dogs do not get tied up, nor do we have a fence, nor do my dogs eat my chickens. Ok, the one German Shepherd we had -might- have done so, he wanted to more than once when he was a puppy, but he was raised with (by?) the Cocker Spaniel who taught him manners. The dogs were trained to stay on the property, I've seen that Spaniel chase a neighbor cat off the property and stop where the driveway ended. The cat ran on and the dog sat down and looked sad with his paws at the edge of the driveway. That cat (Cricket by name) LOVED to torment him that way cause you KNOW he knew the dog wouldn't follow.
It takes patience, and consistency, and calm cautious training. First, they never go outside when the chickens are loose without a leash. When you walk them near the chickens, and they react to the chickens, you say nooooo, (say it don't yell it, don't get them freaked out) You reward with treats and/or voice, you insist on good behaviour, you reassure, you praise, you give firm, not freaked out No's. It's a huge pain for as long as it takes. You can NEVER skip the leash bit if the chickens are out, for as long as it takes for the dog to learn, and you can NEVER freak out and add to the frenzy, because as someone said, they think the chickens are just big flappy squawky squeaky toys and they all need to learn to coexist. Once they're calm around the chickens while they're inside the pen, then you can try carefully while they're outside the pen... Thing is, the fact that they've already learned to act on the squawky toy idea, it's going to be harder still. But it's not impossible.
I admit the Spaniel set the example for all dogs to follow, and his acceptance of the birds was passed on by each dog's attitude long after he died at 17 years of age.
On the 'tie the dead chicken to the dog's neck' thing? Well, I HAVE seen it work, years ago my grew up together best friend's grandfather did it to their cow dog when she went after the chickens once, and she was horribly embarrassed by it. Ol' Sophie never ever got close to the coop again as long as she lived. I think it only works on a certain kind of dog though, not all dogs are smart enough to be embarrassed by it like she was, and Grampa caught her the first time and humiliated her with it immediately, yours has lunched several times now so I think it'd be a waste of time and stench. That old dog would walk a mile to avoid the hen house forever after that incident though.