20 August 2014
During a visit to an audiologist for a baseline hearing test I learned an awesome thing about birds.
This summer (2014) I had my hearing tested because I noticed I could still hear faint rustling sounds with my right ear but not with my left. For a long time my left ear has been slightly “less good” but this spring was the first time I didn’t have stereo for everything. I was looking in the wrong direction for the very quiet birds.
The hearing test showed that my right ear is still above average but I’ve begun to age and am slowly losing the high end of sound. My left ear has lost more than my right — hence the lack of stereo — but for a human I have good hearing. The sounds I’ve lost would only be noticed by a cat (or a birder). Since those sounds aren’t in the “human” range, the loss is not eligible for hearing aids.
But if I was a bird my body would correct the hearing loss.
Birds and humans hear via tiny “hair cells” that line the cochlea of our inner ear. They are not “hairs” at all but actually protein-filled protrusions that vibrate when sound reaches them, then transmit it electronically to the brain. Age, loud noises, toxins, and strong antibiotics can damage these cells. Mammals cannot regenerate the hair cells. Birds can!
The photo above, from a 2004 article at the University of Washington’s Department of Medicine, shows the man who discovered this with a bird that helped him prove it. In the late 1980’s Dr. Edwin Rubel at the University of Washington and Dr. Doug Cotanche at the University of Pennsylvania simultaneously discovered that birds can recover their hearing. After hair cell loss they grow the hair cells back again! (Click here for the 2004 UW article.) Later research uncovered this same ability in fish. Dr. Rubel’s lab continues to study hair cell regeneration, now with zebrafish.
Their discoveries have led to work on a wide range of possible solutions, none of which are perfected yet.
For now, I compensate when I hear a faint bird sound — I turn my head.
Some day, thanks to birds, there may be a cure for us mammals.
(photo of Dr. Edwin Rubel from a 2004 article about his research at the University of Washington Department of Medicine)