Predators directly affect their prey by eating them up. But they can also influence their prey’s population dynamics in another important way, a new study reveals.

While experimenting with song sparrows, a team of researchers found that merely the perceived risk of predation—even if no actual predator was nearby—could decrease the number of offspring produced by the sparrows. And this perceived risk of predation also reduced the survival rates of the fledgling sparrows that were hatched, they say.

The crisis at the Fukushima Daiichi nuclear electricity generating facility, touched off when a tsunami hit northern Japan, has achieved the “key milestone” of cold shutdown where the temperature within the damaged reactors is below the boiling point of water, said Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission (NRC).