This is Bird Note.

As a female wood duck swims across a pond with a dozen little ducklings in tow, we see

her as a good mother looking after her brood.

Well, it turns out that some of the youngsters might not be her own.

Wood ducks nest in tree cavities or nest boxes, and it's well known that they'll sometimes

lay some of their eggs in other ducks' nests.

They'll even lay eggs in the nests of other kinds of ducks, like hooded mergancers and

golden eyes.

Biologists call this nest parasitism, or egg dumping.

It may be a kind of adaptive insurance against the loss of a nesting female's own eggs

or brood.

You don't want to have all your eggs in one basket after all.

But can a female duck tell when another duck's eggs have been added to her nest?

Perhaps.

Sometimes hooded mergancers are frequent recipients of eggs from other species, and

sometimes they'll push the alien eggs to the outer edge of their own clutch, or dump

them right out of the nest.

But not always.

So, back to that brood of a dozen little ones we saw crossing the pond.

It's a good bet that the mother duck has at least one and maybe more fostered ducklings

in tow.

For third note, I'm Mary McCann.

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