Great Horned Owl
Hearing is exceedingly acute in great horned owls.
It is almost impossible to surprise a great horned owl, even when approach is made as cautiously as possible and from the side where no glimpse of the observer could be obtained. Not only is it possible for them to hear the slightest sound, but they can readily localize it. Experiments were made where the observer, concealed, gave various sounds and each time the direction was detected.