Too Many Eggs in One Basket

A few species of ducks that nest in tree cavities such as the Wood Duck and Black-bellied Whistling Duck engage in a strange behavior known as “dump nesting” or nest parasitism in which a female duck will lay her eggs in the nest of another female, or even more than one. Sometimes a nest will be parasitized by several other females and the nest egg total may be in the dozens – even over a hundred in a few cases. Of course, relatively few will hatch. If the female owner of the nest does not become frustrated and abandon it, she may lay her clutch on top of the other eggs and incubate them.
Why do ducks do this? No one knows for sure. Speculations are that it might be due to a shortage of nest sites, inexperienced females not really knowing what to do, or a deliberate attempt to have another female raise the young.

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