Owls possess ears, though they are not visible like human ears, hidden beneath their feathers. These hidden ears are part of an incredibly specialized auditory system, allowing owls to excel as nocturnal predators. Their hearing enables them to locate prey in environments where sight is limited.
Unique Ear Structure
An owl’s ears are not external flaps but openings located on the sides of its head, behind the eyes, concealed by feathers. These ear openings vary in shape and size depending on the owl species, ranging from small, round apertures to oblong slits. Some owls even have movable flaps that provide protection without hindering sound reception. The “ear tufts” seen on some owl species are simply feathers and do not contribute to hearing; they are used for camouflage or communication.
Many owl species have asymmetrical ear openings, with one ear positioned higher than the other and often out of vertical alignment. For instance, in Barn Owls, the left ear opening is typically higher and points slightly downwards, while the right ear is lower and points slightly upwards. This asymmetry can even be reflected in the owl’s skull, appearing “lop-sided” in some species like the Northern Saw-whet Owl or Boreal Owl. This arrangement is key to their ability to precisely locate sounds.
The owl’s face also features a distinctive concave collection of stiff feathers known as the facial disc. This disc acts like a parabolic dish or an old-fashioned ear trumpet, collecting and funneling sound waves directly towards the hidden ear openings. The feathers of the facial disc are acoustically transparent, allowing sound to pass through, while the stiffer feathers around the rim help reflect and direct sound. Owls can adjust these facial disc feathers using specialized muscles, effectively “tuning” their hearing to focus on sounds from different distances.
Pinpoint Hearing Ability
The unique ear structure of owls provides them with precise sound localization capabilities. Asymmetrical ear placement allows an owl to detect minute time differences in when a sound reaches each ear. For instance, a sound from the left will reach the left ear a fraction of a second before the right, sometimes as little as 30 millionths of a second. This interaural time difference (ITD) is primarily used for horizontal sound localization.
In addition to time differences, owls also use interaural level differences (ILD), which are variations in the sound intensity between the two ears. Because one ear is higher and the other lower, sounds coming from above or below the owl’s eye level will be louder in one ear than the other. For example, a sound from below might be louder in the right ear of a Barn Owl. The owl’s brain rapidly processes these subtle time and intensity differences, combining them to create a precise “auditory map” of the sound source’s location in three dimensions: horizontal, vertical, and distance.
This sensitive and precise hearing enables owls to locate prey accurately, even in complete darkness or when prey is hidden beneath snow or dense vegetation. Experiments show Barn Owls can locate and capture prey purely by sound, pinpointing the source to within 1.5 degrees in both horizontal and vertical planes. Their auditory system is acute enough that some species can detect the rustling of a mouse from over 25 meters away, or even the beating of a moth’s wings. This hearing is key to their success as nocturnal hunters, allowing them to strike precisely without relying on sight.