Does anyone know anything about muscovy ducks?

I just moved to a new apartment and there is a muscovy duck with eggs right next to my patio, but today when I went outside there was a male duck standing on top of her biting her on the neck, I yelled at him and tried to shoo him away but he wouldn't stop. She looks week and she won't move. Is this something normal for these kinds of ducks to do? I've seen a male duck peck at his babies when they were trying to get get food and they seem so mean. Is this something that I could fix by maybe sticking a large metal cage over her and bringing her food and water? I don't want her to get hurt, she's so defenseless and I love baby ducks. If there is nothing I can do about the male, does anyone know what is best for these ducks to eat, I know they like bread but maybe something that will help her stay strong?