Barred Owl ear opening
The ears are located at the sides of the head, behind the eyes, and are covered by the feathers of the facial disc. The “Ear Tufts” visible on some species are not ears at all, but simply display feathers.
An Owl’s range of audible sounds is not unlike that of humans, but an Owl’s hearing is much more acute at certain frequencies enabling it to hear even the slightest movement of their prey in leaves or undergrowth.
Some Owl species have asymmetrically set ear openings (i.e. one ear is higher than the other) – in particular the strictly nocturnal species, such as the Barn Owl or the Tengmalm’s (Boreal) Owl. These species have a very pronounced facial disc, which acts like a “radar dish”, guiding sounds into the ear openings. The shape of the disc can be altered at will, using special facial muscles.
Also, an Owl’s bill is pointed downward, increasing the surface area over which the soundwaves are collected by the facial disc.
Great Gray Owl ear opening
The shape of the ear opening (known as the aperture) depends on the species of Owl – in some species, the opening has a valve, called an operculum covering it . The opening varies from a small, round aperture to an oblong slit with a large operculum. All owls of the family Tytonidae have rounded openings with large opercula, while in Strigidae, the shape of the outer ear is more varied.