Do runner ducks go broody?

I have 10 ducks. 3 blue,2 white runner ducks, 3 mallards/rouens(not sure)1 crested blue swedish, and 1 rather large pekin. Out of the 10 I have 2 drakes a mallard and a white runner. Most people tend to say runners will never sit on their eggs to hatch them out. Is this true? What has your experience been with runner ducks. I have one blue runner duck who has a rather large nest with 16 eggs as of today. The nest footprint is small considering all the eggs that she has in there. I'm not totally sure they are all hers though as I have counted more than one egg being laid on some days. Which at least for chickens is not necessarily impossible for one hen to lay 2 eggs a day.
About the nest:
I found it in an area close to the house, hidden in high grass. Due to a small 2ft x1ft board the grass has kind of overgrown which was the perfect hiding spot since only by chance did I notice her their one morning. She has only recently started covering the eggs with a light layer of grass. And as of this morning started putting feathers over it as well. Does this mean she will probably sit soon? Or do all runner ducks go out of their way to make a nest of this sort, just to not sit on them?
I'm hoping she will sit on her nest to hatch them out considering all the trouble she has gone through to make a nest. As for the other ducks they mostly just lay their eggs where ever they are or in a small enclosed area that has wood shaving and just be on their way. The pekin sometimes tries covering the eggs with wood shavings but not with feathers like my blue runner. They are about 27 weeks old and have just started laying within the past 2 weeks.
Blue Runner:
I usually find that she will start to lay around 5am and be there for up to 2 hours. Not sure if this is how long it takes for her to lay her egg, or if she is trying to keep them warm. I do live in texas so temperatures can range from high 70's/low 80's at night to high 90's during the day. So once daylight hits temperatures start to rise fast. So it's quite possible the eggs reach a temp of around 80-100 degrees and stay that way for most of the day being that that side of the house gets full sun with the board sorta of blocking the actual nest for most of the day. As the sun starts to go down the nest gets full sun for maybe an hour when temps reach around mid 80's.

Are these eggs still good and viable?