Ok this morning I went out to my chicken pen to find 3 hens and one duck dead. What hunts during the night to early morning and eats and attacts the head only.?
Weasel. Hard to catch (for me) but it will continue killing until it is stopped. Look around for it's nesting area. They usually stay close to their food supply. In the daytime you will probably find it asleep.
You need to identify this killer. Shore-up your coop but, if you don't know for a fact what predator you are dealing with, you will stay at a disadvantage.
Game cams are now relatively inexpensive.
Using this set-up will alarm you to any movement near your chickens.
There are more expensive motion detectors. I'm assuming they are probably better at detecting movement. You may want to spend the extra money on better detection. I got the cheaper ones and don't regret it. YET!!
When the motion detector sets off the "alarm", you go out and either kill this thing or at least identify it. The other light in the fixture will provide you with enough light to see what you're doing.