We can hear thanks to a complicated arrangement of ear canals, small bones and an eardrum that receives the vibrations of sound waves. These are converted to electrical signals the brain interprets as a noise.
Birds also have these internal noise processors and sound reaches them, and is passed on to their brains, from holes just behind and below their eyes.
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The reason these holes are not immediately obvious is because they are covered in downy feathers called auriculars that are specifically designed to protect them from dust, flying insects and wind noise. In some species there is also a valve present, called an operculum.
Do birds have ears?
For most mammals, though, the first stage of hearing is our external ear apparatus, known officially as auricles or pinnae, that collect and funnel the noise. These pinnae project from the sides of our heads, level with our eyes, and their contours help us work out if a sound is coming from ahead or behind us. Put simply, as we turn our heads the sound reaching our external ears is louder if the source is in front and somewhat blocked by our ear flaps if it’s behind.
Birds have no such external noise channelers so working out where a noise is coming from, especially in their three-dimensional living space, has to be done in a different way. Don’t be fooled by those birds that seem to have visible ‘ears’. Species such as the great horned owl, have what are termed ‘ear tufts’ but they are, in reality, skin projections covered in feathers that are employed to make the owl look bigger and more threatening.
Why don't birds have external ears?
Researchers from the Technical University of Munich, Germany, established the answer to the question of why a bird doesn’t need external ears by examining the heads of chickens, ducks and crows and experimenting with different sounds. They discovered that instead of an external ear, the whole head of the birds is involved.
Birds have slightly oval skulls and this affects the way sound waves pass over their heads. Consequently, each ear detects the sound at a different volume and frequency. The bird’s brain can interpret the different frequencies to give a direction and height to the incoming sound.
In largely nocturnal avian species, such as owls, their ear canals can be positioned at marginally different heights. Establishing the exact location of a prey animal is especially important for them because they are mostly hunting in the dark and do not have the advantage of coupling their hearing with acute vision as a hawk would.
The asymmetrical positioning of their ears, and disc-shaped faces that act like radar dishes, greatly assist accuracy. The Owl Pages website explains like this: “In a barn owl, the left ear opening is higher than the right – so a sound coming from below the owl's line of sight will be louder in the right ear. The translation of left, right, up and down signals are combined instantly in the owl's brain and create a mental image of the space where the sound source is located.”