Birds are gorgeous creatures! Each species has a unique plumage that can sometimes take our breath away! However, there’s one odd thing about them – they don’t have ears! Or, at least, they don’t have visible ears. On the other hand, it’s well-known that birds possess a keen sense of hearing. So what’s the explanation?
Birds have ears but lack the external structure visible in humans and mammals. This allows them to detect the sounds around them, although the range of frequencies they’re sensitive to differs from that of other animals. Moreover, they rely on different techniques to detect the location of the sounds they hear.
Do you want to learn more? Keep reading, as we’ve got some jaw-dropping facts about a bird’s hearing sense!
How Do Birds Hear?
Birds can hear thanks to their ears. Yes, you’ve guessed it right, birds do have ears, but obviously, they’re slightly different from those of humans and mammals.
Bird ears are similar to human ears because they have an inner and a middle ear. When it comes to the outer ear, however, things are slightly different.
Humans have an outer ear organ. Birds, on the other hand, have a unique funnel-shaped opening that serves as an outer ear.
These ear openings are located on both sides of their heads, just behind the eyes. They aren’t visible because they’re covered in what scientists call auriculars – specialized soft feathers. Their primary role is protecting the ears and minimizing the wind noise.
On the other hand, it is essential to note that the external ear structure in humans and mammals helps them establish where the sound comes from. In scientific terms, it is called sound elevation. So if birds lack this external structure, can they localize where the sounds come from?
A study shows that birds can establish the elevation of a sound source even without an external structure. The research focused on how chickens, crows, and ducks hear and revealed that a bird’s head played a major role in detecting the sound location. In easier terms, each bird ear registers noises at different frequencies. The frequencies of the noises registered in the right eardrum and in the left eardrum depend on the angle where the noise comes from. As such, the position of the head affects the way the bird hears something.
Another interesting phenomenon that affects the bird’s ability to determine the sound elevation is ear positioning. This is best illustrated by the anatomy of an owl’s ears. Since most owl ears are positioned asymmetrically, the sounds arrive in both at slightly different times – we’re discussing a period of only 30 millionths of a second. It seems nothing to us, but this difference plays a key role in establishing where the sound comes from in owls.
Here are some other things that are different in bird and mammal ears:
- While mammals have three ossicles, birds have only one ossicle. Ear ossicles are bony elements that play a part in transmitting vibrations from the eardrum to the inner ear.
- While mammals have a coiled cochlea, birds have a straight or slightly curved cochlea (a part of the ear where the hearing takes place) whose length varies depending on the species; the length and the form of the cochlea affect the range of frequencies birds can detect; the longer the cochlea, the better the sensitivity to frequencies.
What Can Birds Hear?
Studies show that most bird species can hear sounds produced at around 1-4 kHz. However, some may be sensitive to higher or lower frequencies. Pigeons, for example, are most sensitive to sounds registered at 1-2 kHz, but if required, they can register sounds of up to 10 kHz.
By contrast, the ring-billed gull is most sensitive to sounds of 0.5-0.8 kHz frequencies, and the upper limit is only 3 kHz.
Considering these details and the fact that the frequencies of human voices range from 80 to 255 Hz, we can assume that birds can hear humans talking. They might also be able to hear music if it’s played at a frequency they’re sensitive to.
Can Birds Hear Worms?
Based on the information above, we can definitely suspect that birds can hear worms moving under the soil. In fact, this has been confirmed by a study focused on whether robins could rely on hearing alone to find worms.
However, other studies show that birds are less sensitive to specific frequencies, and while humans can hear faint sounds, birds might not be able to detect them. Moreover, research shows that worm movements produce sounds of around 40 Hz (much lower than the lower limit of a bird’s sensitivity), it’s unknown how exactly birds can hear them.