I don't have any direct experience with llamas, but have a few friends that have alpacas to protect their sheep. They don't bother with the handlers (or me - being an outside visiter either), but I've been told that they beat the snot out of a coyote and the neigbors dogs. I was just wondering if they would get protective of birds, or if they would just be protective of their space? Or would they not be protective at all if there weren't other sheep/alpacas around? Does anyone know if they would go after a fox?
The llamas I've seen seem to prefer to defend their space by spitting or upchucking on their perceived enemies. As to the usefulness of a llama for providing flock defense, to a llama everything and everyone is an enemy.
Do be advised that a equine can pick up a broken grain of corn off of the ground. It would seem that some way needs to be devised to protect the chickens rations from the donkey. Or you could put the donkey inside the chicken's pen after dark. Try it, you'll never know unless you do.