Yes, she will set on a nest of nonfertile eggs.

The sex drive of male mallards is incredible. Especially this time of year when the hens are all setting and are unavailable, or the unattached males are just dieing to get some action. It wouldn't surprise me a bit if they flew in for a romp every day, assuming that you have an uncovered pen, which you must, or why would you even think that they could have bred her? The big danger with that set up, is that she is dead meat if any predators happen by. They don't call them sitting ducks for nothing, although the proper term is "setting".

If the eggs are fertile, you can tell now by candling them with a flashlight. If any are clear, throw them out, leaving the others, and get rid of the ball. If they are all clear, take them, so she'll start laying for you again. You should also know that Campbells, as a laying breed, are notoriously poor mothers. You'll find many exceptions, and people delight in bragging that they have one who sets full term and actually raises the young to boot. Still, those are the exceptions, and in general, even if they do set, they have a high rate of abandonment of eggs, or of ducklings, if they get that far.

Of course all birds do have variations, like I have some guineas that are great setters, and I have some that are lousy setters...and some that won't set at all. If you have a large dog that you can tie out near your duck, that helps keep raccoons away. I had a guinea make a nest in some mint I have growing wild, and I would spread some mint around while she was on it...she actually had a successful hatch and didn't get eaten! I even walked our dog over to where she was hiding to see if he could sniff her out (he's got a great sense of smell), and he didn't know she was there.

Also, if you do candle the eggs, make sure to wait until they have had time to incubate a little.

Read carefully. The bird has been setting for two weeks already. PLENTY of time to show development if they're candled now.

In future, you might like know that duck eggs are great for cooking with, esp. baking. I know of people who substitute them for hen's eggs on a regular basis for all uses, but personally, I don't like them cooked directly - the white gets a more translucent look than hen's eggs when cooked, and I guess a lot of my food preferences are visual, as it puts me off frying or poaching them, or even scrambling them. However, that's my feeling... If you collect the eggs daily, the duck(s) will keep laying for quite a while, unless they go broody.

We have a domestic duck that has been sitting about 2 to 3 weeks and today we noticed that she had uncovered her eggs she also seemed very excited. Could they be ready to hatch?

28 days for Mallard type ducks.