Yep, raccoon is my guess as well, although I know of possums, minks and skunks all doing this very thing. We have chickens and ducks as well and have lost a few over the years to predators. We have fox, weasels, raccoons and coyotes around. If it were a fox or coyote, they would take the whole bird. Not raccoons, though. Raccoons are dicks. Also could be an owl. Owls will take the head off prey at times, then come back for the rest when the coast is clear.