Cowbird Mafia

Turns out cowbirds weren't merely duping the host birds into taking care of their eggs and offspring; it was blackmail, pure and simple. National Geographic News notes:

"Cowbird mothers keep watch on the nests where they've laid their eggs.
"If the birds find that their eggs have been destroyed or removed from the nest, the cowbirds retaliate, the study says.
"The birds reportedly destroy the host birds' eggs, pecking holes in them or carrying them out of the nest and dropping them on the ground."

Not all ornithologists are convinced by this new study, as the cowbirds' deprivations weren't caught in the act, but the proponents say they have ruled out all other possibilities.