How to encourage ducks to go broody?

We have a mixed flock of 10 duck hens with 1 drake. I'm trying to hatch a new brood for the Spring. I've set up a new sheltered nest and kept it loaded with 10-13 fresh eggs for the last couple weeks, but none of the hens seems interested. They do like laying in the nest (so much so that one of our chickens has taken to laying in it!) Is there anything else I can do to encourage a hen to set? More eggs, less eggs?

Our flock is made up of Pekins, Roans, Indian Runners, and Khaki Campbells. I've heard these breeds have all had the brood instinct largely bred out of them. Does this mean we'll wind up incubating?

I've also heard there's not much you can do to encourage broodiness except maybe hold a hen on a nest for a while. Anyone tried this?

Thanks ~ Naga

With the Muscovy flock that I'm familiar with, some of them would go broody in the conveniently provided locations, but others would only do so in hidden spots of their own choosing; tall grass, or under tarps, helpfully. Perhaps providing a wide variety of potential sites might help, if these aren't already available?

Downside, of course, is that this also encourages them to lay all over the place...

Interesting idea, Dillon. They do like to lay under a large salmonberry bush. I usually just collect those eggs as soon as I see them, of course, but I could try letting them build up and see what happens. The downside is that it's outside the coop, so the hen wouldn't be protected from predators at night. We have a fair number of racoons in the neighborhood. I suppose if a duck does decide to set there, I could rig up a makeshift enclosure for her.

Once a duck was being persistent about sitting on eggs, we would collect her and the eggs and put her inside an existing dedicated enclosure.

Two person job ideally; 1 grabs the duck, the other moves the eggs to a nice nest pile inside the enclosure, then 1st person adds the duck. Usually she'd go right back to sitting. We'd keep the broody duck locked up til the eggs hatch, or it becomes apparent they won't be hatching; some of the ducks were just not interested in staying on the nest long enough. Once we'd identified these, we would not let them start to sit; no sense wasting eggs. If two+ went broody near the same time, the known good brooder/mother got all the eggs.

There is some leeway with duck brooding times since they will generally keep sitting after the first duckling emerge; so, even a couple days after starting to brood, warm eggs could be added to bring up the clutch size if the sitting duck isn't producing a large clutch on her own. However, too many eggs, and they won't all stay warm enough. We aimed for 12ish.