The ear hidden beneath a feathery funnel
Barn Owls rely on their superb sense of hearing to survive, because they use it to find prey. Imagine finding small mammals like the Short-tailed Vole beneath a cover of tall grass… sound is very important.
What helps a Barn Owl to be so good at hearing?
The face of a Barn Owl is flattened out and almost circular when the owl is alert, but as it relaxes, the “facial disc” falls into a more heart-shaped appearance. The distinctive face is actually very practical, funnelling sound towards the ears.
A ridge of feathers between the eyes effectively splits the face into 2 dishes collecting sound waves. Feathers are arranged in a way that carries sound into the ear openings, which are hidden beneath.
THE POSITION OF THE EARS
Like you, an owl will turn and tilt its head about to help it focus on the position of a sound. Like you, an owl has its ears on each side of its head (hidden by feathers) and so sounds from one side will hit the ear on that side first. These things help owls recognise whether a sound is coming from the left or right – that is, within the “horizontal plane” relative to the position of the head.
But as a flying hunter, usually approaching prey from above, detecting prey in the “vertical plane” is crucial too. Every Barn Owl has its ears positioned at slightly different levels on each side of the head. The left ear is higher than the right. Also, the right ear points slightly upward, and the left ear is naturally pointed slightly downward.
This helps the owl to know whether it is hearing something happening “above” or “below” its face – that is, in the vertical plane.
THE EAR ITSELF
The ear opening of an owl is almost a rectangle in shape, about 8mm by 5mm, rimmed with pink skin which holds a few fine, tiny feathers. There is also a feathered flap of skin between the ear and the eye, which acts as an ear cover. The ear covers are probably in slightly different positions when the owl is relaxed, or when it is alert.
The ear of a Barn Owl is most sensitive to the frequencies of sounds that a small mammal might make. While hearing a mixed noise, it particularly focuses on sounds between 6kHz (kilohertz) and 9kHz.
Barn Owls are excellent at detecting the subtle sounds of their prey, and their brains are very good at using sound information from the ears. Recent studies have found a strong sounds memory in Barn Owls. After fixing on the position of prey, they can be distracted temporarily, but remember the same place accurately afterwards.
Barn Owls are also silent in flight, so their own movements do not interfere with the need to hear clearly. The leading flight feathers (“primaries”) have a fine fringe on the leading edge, and the main wing feathers have a velvet-like topside that cuts smoothly through the air.
The information in this fact-file (and many others) comes from the book by Colin Shawyer “The Barn Owl”, published by Arlequin Press – ISBN 1900159 70 8. The book contains scientific references to studies on Barn Owl hearing.