If I had a nickel for every one of these heartbreaking and horrifying dog-attack-chicken stories, I could rule the world.
I'm so sorry. I hope you find the missing birds and that they will recover. Everyone needs Rescue Remedy in their water for awhile to help with stress. You will have your hands full with medical treatments - oh how I feel for you and them. it will be a very trying time. First, to make sure the ones still alive do not die from shock - they need to be kept warm and comfy.
I hope you know or can find the people with whom these dogs should have been and that they receive the maximum bills (including all vet bills) and awareness about the death and destruction their irresponsibility caused. Until then, your remaining birds are stuck in lockdown - the dogs will return.
JJ