Okay...read up and maybe it was a snake! The head and neck seemed to be chewed on and wet, the body dry and unharmed. Maybe a large snake killed and tried to swallow, but couldn't get it down and regurgitated it? No blood, so something that constructs or poisons makes sense.Oh
I am so sorry, chicks are quite fragile and until they are at least a couple months old I hold my breath each day.
Could this be the work of a snake? I have large snakes that could take a small chick but I don't think anything the age of your chicks.
I cropped the prior pics. But her head seemed most "plucked".