The long story being that my second heat lamp went out and I couldn't get to the store any time soon to buy a replacement. Desperate for something to keep them warm, I spied my adjustable temperature dehydrator and put it to work sitting over top of the bin on wire. To my amazement, the bin full of duckies with the dehydrator top was doing overall much better than the one with the heat lamp, especially during watering time. They do go through more water overall than the heat lamp bin, but they seem to be larger (if I could find my scale...) and they certainly dry off faster after they're watered. The best part is that since it dries out the litter as well, I only have to change it every other time I change the heat lamp's bin! I don't think it'd be as useful for chickens, but for waterfowl I don't think I'll go back to a regular heat lamp. TL;DR: I found that a heated fan is much better than a heat lamp for brooding duckies.