Poor dear. Gareth noticed a few days ago when he let the ducks out in the morning that Nancy Drew was limping. He brought her in, and I looked closely at the foot and leg and couldn't find anything amiss. No scratches, no swelling, no redness, nothing different at all from her other leg.
I checked online and found that a limp can be caused by a rip or object in a foot, which would be seen, or an infection, which would be swollen, red, and/or hot. They can get something called "bumblefoot" which sounds more like a Beany baby than a disease. But that's from not having fresh straw to walk on, so that they walk in their manure. Not the case here. And then there was the "other" category. I found lots of duck owners who had individual ducks with just a "mystery limp". Some ducks got better in a couple of weeks, others always kept that limp. Rest was recommended as much as possible.
Nancy herself is resting quite a bit. Nigel has been putting the ducks in the barn earlier, as well, and Gareth pushed his barn opening a half hour later. And several days we've brought all of them in for a lonnnng bath in the tub so that she can float to rest the leg, and get plenty of water and extra food in the form of torn-up lettuce that we throw in the tub. The others are foraging, but she is not. This has helped, or else she would have gotten better slowly anyway, because her limp is getting less pronounced.
The ducks are officially old enough to lay eggs as of this week, but of course are less likely to do so because of the short days. We don't have artificial light in the barn to stimulate them, so it will be interesting to see if they start laying before the days get longer in the spring.