Hmm, I'm not sure then. The nearest I have to a wild mallard is a Call Duck Mallard Drake who comes and goes as he pleases, and I'm not expecting any eggs from him!
I would imagine that wild ducks may well lay less than domesticated ones. I'm not sure if ducks would have more than one set of young within the season either. It certainly sounds like eggs are being thought about. I hope she is not egg bound - although I think you would know about that too, as she would look like she is straining.
Maybe you should buy some fake eggs, or a golf balls, and put them in the nests, and see what happens? I bought 3 fake duck eggs and put them in the duck nests in their house the second week of February. A week later they were laying. I did however thing they were showing signs of starting to lay before I put the fake eggs in, ie wandering from home.
How long have your mallards been living in the run for? Are they quite tame? One of my ducks just lays randomly late in the morning, so we are losing her egg, as they are free range but just get locked in their run at night. I have also found an outside nest one was laying in. They can be quite fickle - coming over all broody, then just loosing it again, although I would think wild mallards would be less like this.
