Just hearing recordings of predators caused sparrows to raise fewer babies
Nothing but fear itself can actually be dangerous for nesting birds.
Song sparrows protected from attack but subjected to recordings of predator yowls and leaf-crunching approach noises raised 40 percent fewer offspring in a year compared with neighbors living amid innocuous noises, says population ecologist Liana Zanette of the University of Western Ontario in Canada. Predators do not need to kill a single prey to have a big effect, she says.
Scary noises, broadcast where the sparrows nested in the wild, took a toll throughout the breeding season, Zanette and her colleagues report in the Dec. 9 Science. The alarmed sparrows laid fewer eggs to begin with, and they proved such