It's contagious that's for sure.
Right before hatch I move nest box with mama chicken into the same set up I do for my ducks. Gives mama protection and gives her time to bond with her chicks, I can relate about broodies I have 3 Bantam cochin broody [I have 2 rooster one is too old and isn't fertile the other is too tiny to bred so no fertile eggs] and 2 Muscovy that are broody, I don't let them hatch because I have 3 drakes and don't need any more.
Your broody chicken must be large to sit on 8 duck eggs.
Right before hatch I move nest box with mama chicken into the same set up I do for my ducks. Gives mama protection and gives her time to bond with her chicks, I can relate about broodies I have 3 Bantam cochin broody [I have 2 rooster one is too old and isn't fertile the other is too tiny to bred so no fertile eggs] and 2 Muscovy that are broody, I don't let them hatch because I have 3 drakes and don't need any more.
Your broody chicken must be large to sit on 8 duck eggs.