Besides laying eggs in her own nest, any female wood duck will lay an egg in the nest of another female wood duck if she sees the other duck leaving her nest  Under natural nesting conditions, this parasitic behavior is relatively rare because the ducks' nests are well hidden  However, when people put up nesting boxes to help the ducks breed, they actually undercut the ducks' reproductive efforts
These nesting boxes become so crowded with extra eggs that few, if any, of the eggs in those boxes hatch
The nesting boxes would be more effective in helping wood ducks breed if they were less visible to other wood ducks than they currently are.