Leaving Eggs in Other Duck's Nests

Sitting in the kitchen looking out the window watching wood ducks float on Cindy's pond. That made me think about where their nests are. Found out some more about these ducks including this item from Google.

Interesting notes: The female wood duck has the unusual habit of laying some of her eggs in other wood ducks' nests, leaving the raising of the nestlings to another female. Called "brood parasitism" or "dump nesting," one study showed that over 50% of wood duck nests may contain eggs from more than one wood duck (Semel and Sherman 1986). Some nests have been reported to contain eggs from as many as four or five different wood ducks (Belrose 1976). What would cause this behavior? The most obvious answer is that the female is then relieved of child-rearing duties, however, this doesn't explain why a female that has dumped some of her eggs in another wood duck's nest will still make her own nest and raise young.

A currently accepted theory, for all animal behavior, is that each animal is driven by the need to leave offspring. In contrast to the old, and no longer accepted, idea of "survival of the species," most animals act in ways that will insure their offspring's survival. If the female wood duck leaves some of her eggs in another wood duck's nest and also raises her own, she increases her chances of leaving more offspring (Davies 1991).