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Ears

Barn Owl (Courtesy NEBRASKAland Magazine/NGPC)

Those tufts of feathers you see on an owl's head might look like ears, but they have nothing to do with hearing. You can't really see a bird's ears on the outside, because a bird's hearing structure is almost entirely on the inside.

A bird's ear openings are actually located behind and slightly below its eyes. On most birds, the ears are covered by barbless feathers that protect them from turbulence while flying but still allow the bird to hear.

A bird's ears have parts that enable it to hear as well as other parts that control the bird's balance when it stands, hops, swims, or flies. (The balance structures work separately from the hearing structures.)

Like human ears, bird ears have three sections: the outer ear, the middle ear, and the inner ear.

• The air-filled outer ear canal channels sound to the eardrum.
• The air-filled middle ear sends sound vibrations from the eardrum through a bone (the columella), to another membrane.
• In the inner ear, the vibrations from the columella are sent to a fluid-filled chamber where hair-like cilia convert the vibrations to nerve impulses that receptors carry to the brain.

Birds are able to hear a wider range of sounds than humans. Bird hearing has better resolution than human hearing, so they hear much more detail. Birds "hear faster" – that is, they can hear much shorter notes than you can. Humans can process sounds in bytes about 1/20 of a second long, but birds can distinguish notes up to 1/200 of a second. This means where we hear only one sound, a bird may hear as many as 10 separate notes!

A songbird uses its keen hearing to recognize another bird by its song. An owl uses its hearing gifts to hunt for food in the dark of night.

Nocturnal owls have the most hearing receptors in their brains and they have asymmetrical (different on each side) ear openings. One opening is higher and one is lower to aid in locating prey at night. Because of the difference in the location of the openings, an owl will hear a sound at two slightly different times. The owl uses that very small difference – a 30 millionth of a second, in some cases – to figure out the "left/right" location of its prey. Birds of prey also have asymmetrical flaps in front of their ears that help with figuring out the "higher/lower" location of prey. Being "quiet as a mouse" is not much defense against hearing like that!

Other ear facts worth a listen:

• The Great Grey Owl has hearing so sharp it can hear a mouse moving around under a covering of snow.
• Owls use their eyes to hear. Those large, round structures around owl eyes are really there to catch sound waves. The owl's beak is flattened to keep it out of the way, and the owl tucks its beak downward to aid the sound collection process.
• Woodpeckers use their hearing and distinct patterns of drumming to keep in touch with their mates while they're out finding food.
• A small number of birds use echolocation, as bats do. Some penguins have this ability, but more often the birds that have it are cave-dwellers.