MichikoSaur,
Sorry to hear about this attack. I see that you are in Tex.....and I just had a similar experience 3 days ago in the N. Hou area.
I have a condo with a pond where the "yard ducks" live and my 2 adults live in my yard & patio area. I watched a big bird sit on the park benches, walk around the grass, fly over to a balcony and walk around on the concrete and just hang out. He did this all afternoon. Thought it was a red-tail hawk. The pond ducks were suspecious at first as thier instincts directed them to be. But, as the day went on they became comfortable with this great bird of prey standing there like stone. A Pekin hen paid the price for that.
After I discovered what had happened I got another guy and we were discussing what to do about this and as we spoke in the yard the bird flew onto MY patio and attempted to grab one of MY ducks! After that failed attempt he then took another run at ducks in the water and missed. One kill was not enough for this guy. He finally just got up and flew away and has not been seen since.
My first thought was a hawk. However, after doing some research and speaking to some folks that know, I was informed that this was a Golden Eagle and that he could have ripped me to pieces had we come too close to "his" kill or to him. This bird was absolutely fearless and stood there staring at us as we threw rocks and whatever we could find trying to run him off....he just looked at us directly as if he were sizing US up....
I was told that Eagles are making Texas home now for some reason. They have been sighted in several neighboring towns and communities. Hawks are one thing, but an Eagle? theres little defense against those outside of bringing potential prey indoors. At near 2 ft tall with a 3.5 ft wingspan and talons the size of my hand, thats a ferocious preditor.
My birds were shook but recovered pretty quick. They did not get "grabbed" like yours did, but it was close. I'm guessing the cold weather has the preditory birds all searching for their prey anywhere they can find it. I'd hate to have to do something drastic if this creature returned, it is truely a magnificent bird....graceful yet powerful with wing beats that you can hear, slow but powerful. If it came down to it and I had opportunity, I'd protect my ducks with whatever was available, meaning whatever shotgun shells were handy.
If your duck was injured physically, the treatment that I use that works wonders is an increase in fresh greens, cabbage or lettuce, some carrots that have been grated/chopped fine, vitamins in the water and a few drops of apple cider vinegar in the water. I mix that food blend with their mash and maybe some rice and it works wonders. The vinegar is a miracle cure-all for ducks. Isolation (rest/quiet) and warmth from a heating pad in a box and they seem to recover from trauma much faster.
Good luck and I hope that your Owl has moved on...