ropntoz, it is good to see someone who has studied or worked directly with birds post a straight-forward admission that a protected bird of prey just might perform an undesirable act w/o citing this study or whatever that would indicate otherwise.
Additional thoughts:
An owl will eat starting at the beak - yes, they eat the beak - and down the neck till they have access to the internal organs, then they will eat those. In essense, hollowing out teh body cavity. YOu could take the remains and pluck and have perfect main ingrediants to chicken and dumplin's. A coon, etc... may start with the head, but usually will hit the breast and/or split the carcass when they get down that far.
Weasels attacks are often not fatal on an adult chicken. They are usually to blame for mass killings of yound birds where often the only sign of attack is a bite mark to the back of the neck. Vampires, to be seasonal.
If you have an owl getting those chickens, or whatever proves to be the culpret, he will not stop until you are out of chickens or he gets "rehabilitated" ....permanently. Look for the attacks to take place right at dusk or daylight. Daylight, in particular. The chickens stir very early while owls are still active.