How do birds hear?

Birds rely on their keen hearing to detect prey and identify other birds based on their songs. In fact, birds have better hearing resolution than humans, so they can hear more detail. However, birds lack the external ear anatomy that humans rely on. So how do birds hear?

Birds have ears, but their ears are structured differently than human ears. Birds and humans both have inner and middle ears. However, birds differ from humans in that they lack external ear structures. Humans have external ear organs, and birds have a funnel-shaped opening that serves as an external ear, located on either side of the head. These openings are usually located behind and slightly below the bird's eye. They are protected by soft, spineless feathers called ear feathers.

The position of a bird's head also plays an important role in its hearing ability. Scientists have determined that different frequencies of noise are recorded on either side of the bird's head. Depending on the angle at which the noise is generated, the left eardrum will register a certain frequency, while the right eardrum will register a different frequency. The frequency difference between the eardrums allows the bird to locate the source of a sound.

Owls, for example, are known for their extremely sharp hearing, which helps them locate prey at night. This hearing ability is due in part to the asymmetrical arrangement of the ear holes, with one hole lower than the other. Sound is recorded in these openings at slightly different times. Owls can use this time difference (sometimes as little as thirty millionths of a second) to determine whether a sound is coming from their left or right. Other birds of prey have valves in front of their ears that help them determine whether a sound is coming from above or below them. Some owls do have ears on the top of their heads, but these are actually tufts of feathers controlled by small muscles under the skin and do not affect their hearing at all.

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