Bad Quail Behavior or Predator?

I've been hatching and raising quail for a few months now and am probably on my 6th hatch. But a few days ago, I found one of my mature quail with a split scalp. I couldn't account for the wound. But today, three of my 3 week old quail had similar but worse wounds on their heads. Is this a result of quail bullying or a mark of a predator? My quail are in hanging cages of 1/2 in square hardware cloth. I see no signs of entry to suggest a predator and if it was something like a rat, why would it only scalp them and not eat them? The quail have more than adequate space, feed, and water and have no reason to abuse each other. I'm at a loss!

How tall are the cages?  Could the quail be hitting their heads when startled?  I used 1/2 inch square hardware cloth with success despite high predator pressure so I think you are right that it's unlikely to be a predator.  I can't remember if Bullying would have been loss of feathers from their backs or their necks.  It's been over a year since I had any.