Sorry to hear about the hawk but glad your duck was only injured a bit and seems to be doing okay.
If you are in an urban or suburban area, hawks tend to be a bit more aggressive and much less scared of people. If legal in your area, you can shoot a round of whatever is you loudest firearm into the ground to scare the hawk. DO NOT try to injure/harm the bird, all raptors are protected by federal law.
I am in the country and the hawks here have taken some of my young chickens when they were in the pasture. But, they high tail it when I walk outside even from 200' away. Recently, I had an adult chicken taken by a hawk at the edge of the woods but just inside. I hapened to go out and as soon as it heard the door close, hopped from the ground to the tree and flew off. Then the crows gave chase. I happened to stay outside for quite some time and a bit later, it came back with a friend. I fired a 9mm round into the ground and the hawks literally turned tail and flew off.
If you cannot fire a weapon, anything loud and somewhat unusual may help. Shouts may or may not work. Fireworks the popping kind not the big pyrotechnic type, if you can find them now and again if legal, may work. Air horns, pots and pans banged together etc.
A permanent deterant is best. Netting or fencing on the run's roof. I have had really good luck with fishing line. Knock on wood. In a very open area outside of their run I put up two 10' pieces of pvc pipe with fishing line attached to the top running out to the fencing. There are pieces of frayed, colored rope tied along the fishing line to make it more visible. I have not had any losses in this area at all. Again, knock on wood.