She's a "bad" mom because ... she abandons "castaway" chicks. Mother grebes build floating nests of rotting vegetation where both parents incubate two eggs until one hatches.
But "once that first chick hatches, [the parents and baby] swim away from the nest and leave the other chick all by its lonesome," Forbes explained. "They are just interested in getting one successful chick off the nest."
Give Mom a break, because ... grebe mothers are simply producing an "insurance offspring"--at least one baby will survive even if there's a problem with the primary chick. "It's pretty routine in large predatory birds," Forbes noted.