Did she fall for something or accidently get dropped? take a towel and make it into a donut place your duckling down into the towel head up this will support your duckling till you can calm down and we try and figure out whats going on. Tell us exactly what happened how old is your duckling too?
I'm sorry other than keeping him in a secure place and watch to see if he recovers I'm not sure what else can be done. Supportive help right now just don't let any other ducklings be with him till you know if he is going to recover or he may get trampled on and injured worse. Breathing normal is a good sign where do you have him?
I would not give him water with a dropper. Hold the water dish up to his mouth and let him drink. Have you given him electrolites? Hold the food dish up to his mouth also. Try to let him eat and drink on his own. You may have to hold him while he eats and drinks.
