When they do that they're not fertile or have gone bad ie they're no longer alive in there. Just remove them if you see them out. Also it's a possibility that she's on too many eggs. Sometimes other hens will lay their eggs near the sitting hen then push them under her! Nice huh? I always candle my eggs first before I throw them away. Don't leave them there or the birds MIGHT eat them.
no fraid not
Ducks lay their eggs on a nest, whether it be in a tree or out on the open ground.
Ducks lay eggs, usually in a nest. This nest may be on the ground, or up inside of a tree trunk.
Mostly the ground in thick bushes to hide their nest easier
they might be duds
She gets off the nest to eat, drink, and get wet, in order to provide humidity in the nest.
No, not if you want the bird to return to incubating the eggs.
Not by choice. They usually nest in tall grass or weeds.
No, they occasionally leave it to get water and/or food
Yeah, most likely, especially if her young are still there. This is not, of course, reason to disturb her nest yourself. And actually, under the Migratory Bird Act, it is illegal to disturb the nest, eggs, or young of native birds.
The cow bird. The cow bird lays it's eggs in another birds nest, and then when the cow bird's eggs begin to hatch, the baby cow birds will push the other birds out of the nest.
No, doing so may cause her to abandon the nest. Ducks do choose strange places to nest but are frequently successful. Try protecting the nest environment without disturbing her.
Not normally. If you take a look in a nest where the eggs have hatched the shells are usually in a zillion pieces in the bottom where they have been crushed by the adult and chicks while the chicks dry before leaving the nest.