Monica Retamosa was in the middle of changing the batteries of a tape recorder when she heard a bellbird for the first time. Standing on a forest floor, she looked up into the trees, scanning for the source of its metallic and powerful sound, searching for the bird for half an hour to no avail. The bellbird sings from the treetops where it is visible to its peers but invisible to those below. Still, Retamosa smiled: She cares for ecosystems in Costa Rica’s AmistOsa Biological Corridor by listening to them.
In nature, living things use sound for almost everything. They make calls to attract mates, communicate identities, warn of dangers,