I have a mallard duck that has currently got 20 eggs in her nest, but she still isn't sitting on them. She keeps them covered with hay, and appears to keep them turned, so I thought she was going to sit. She is currently housed with her drake, closed in at night and allowed to go out during the day. Is there anything I can do to encourage her to start sitting? Or is she just plain and simple not interested? I don't have an incubator so I can't try hatching them, nor do I have a broody hen How long will the eggs last before they are no longer hatchable?