How are the hens protected from predators?

The high fences keep out predators during the day, and at night they are safe in the sheds. The hens are checked throughout day. We see the odd bird of prey but they have not been a problem. If the birds were left out at night foxes would probably be a concern, we don't generally see them but they would probably be around. We have been considering introducing Maremma dogs, which make highly skilled guardians for flocks.