My black swedish duck is brooding her second nest of eggs. She sat on her first nest for about 3 weeks, then abandoned it and took over another ducks fresh nest about 1 week ago. Friday when she came out of the pen for a swim, she was 'goose stepping' - raising her feet up to her belly while she walked - she acted a little wobbly, but seemed to recover. I thought maybe she was just stiff form setting for 4 weeks. Saturday I was leaving for a farm swap wit some chickens when sh came out of the pen. This time, she walked like a drunk. When I approached to pick her up, she tried to run away quacking loudly (she is always quacking loudly), got 2 steps away and fell. Then every 2 or 3 steps, she stumbled and fell. I picked her up and checked her legs, feet, back - basically all over and could find nothing wrong. No sores on the feet, no breaks in the legs, hips seem fine. So I put her back in the pen with food and water (and the other 2 brooding ducks) and locked the gate. She was still setting when I returned later and seemed fine. I have not given the pen a good cleaning in 4 weeks because they are nesting and every time I go in the pen, they jump off their nests and run quacking, or sometimes just scrunch down and hiss. I didn't think it was good to get them that upset (as one of the other ducks has ducklings hatching daily) It is getting gamey in there, so I am going to clean it and replace the litter. I will try not to upset them. I have been feeding layer pellets and a little scratch grain mixed in. They get their water in a bucket fresh every morning and evening and 2 wading pools to play in. When the ducks come out to swim, one of my drakes is very amorous and determined to mate with them, and the alpha drake has to push him off. I am worried that maybe he has injured her? So I am cleaning it today. I guess I need to separate the Romeo (akk another pen!). Is there anything else I can do? should I try adding vitamins to the feed or water?